Aneurismas de arteria cerebral media: avances en las técnicas microquirúrgicas y resultados del tratamiento

TESIS POR COMPENDIO DE ARTÍCULOS Departamento de Medicina Aneurismas de Arteria Cerebral Media: Avances en las Técnicas Microquirúrgicas y Resultados del Tratamiento Ana Rodríguez-Hernández Dirigida Por: Rosario Sarabia Herrero Iñaki Arrese Regañón Pedro Enríquez Giraudo Aneurismas ACM A. Rodríguez-Hernández 2 Aneurismas ACM A. Rodríguez-Hernández 3 Facultad de Medicina Departamento de Medicina Aneurismas de Arteria Cerebral Media: Avances en las Técnicas Microquirúrgicas y Resultados del Tratamiento Memoria presentada por Ana Rodríguez Hernández para optar al grado de Doctora por la Facultad de Medicina de la Universidad de Valladolid DIRECTORES Rosario Sarabia Herrero Jefa del Sª de Neurocirugía H. Universitario Río Hortega Profesora asociada Facultad de Medicina Universidad de Valladolid Pedro Enríquez Giraudo Sº de Medicina Intensiva H. Universitario Río Hortega Profesor asociado Facultad de Medicina Universidad de Valladolid Iñaki Arrese Regañón Sª de Neurocirugía Coordinador de la U. Patología Cerebrovascular H. Universitario Río Hortega Universidad de Valladolid Valladolid, a 7 de Septiembre de 2015 Aneurismas ACM A. Rodríguez-Hernández 4 Aneurismas ACM A. Rodríguez-Hernández 5 “What is right is not always popular and what is popular is not always right.” Albert Einstein (1879-1955) Aneurismas ACM A. Rodríguez-Hernández 6 Aneurismas ACM A. Rodríguez-Hernández 7 A Celia, en honor a la memoria de su madre Aneurismas ACM A. Rodríguez-Hernández 8 Aneurismas ACM A. Rodríguez-Hernández 9 Agradecimientos Aneurismas ACM A. Rodríguez-Hernández 16 Aneurismas ACM A. Rodríguez-Hernández 17 RESUMEN El tratamiento de los aneurismas cerebrales ha cambiado radicalmente desde la publicación del ISAT (International_Subarachnoid_Aneurysm_Trial), que provocó la adopción generalizada de una política pro-embolización en la que la cirugía se reserva solo para aquellos casos en los que fallan los tratamientos endovasculares. Sin embargo, este nuevo algoritmo terapéutico es foco de importantes controversias y numerosos autores plantean serias dudas sobre su validez científica. En el caso de los aneurismas de la arteria cerebral media (ACM), una de las localizaciones más frecuentes de aneurismas intracraneales, el nuevo paradigma terapéutico ha generado, si cabe, más dudas y confusión. Estos aneurismas se han considerado clásicamente complejos para el tratamiento endovascular y, en cambio, favorables y fácilmente accesibles para el tratamiento microquirúrgico. Además, las técnicas microquirúrgicas han avanzado notablemente en los últimos años, permitiendo un tratamiento aun más eficaz y seguro de los aneurismas de ACM complejos. Este trabajo pretende explorar la hipótesis de que los aneurismas de ACM son un claro ejemplo de aneurismas cuyo tratamiento quirúrgico sigue ofreciendo actualmente resultados muy superiores al endovascular. Para ello se revisa la base de datos prospectiva del Servicio de Neurocirugía Vascular de la Universidad de California (San Francisco) en la que, durante un período de 13 años, se incluyeron un total de 2455 aneurismas tratados con microcirugía, de los cuales 631 fueron aneurismas de ACM. Los resultados clínicos y radiológicos del clipaje convencional y de los nuevos avances técnicos en microcirugía, se analizaron y se compararon con los resultados de otras series de tratamiento quirúrgico y endovascular identificadas mediante una revisión sistemática de la literatura. Los resultados obtenidos se han condesando en las cuatro publicaciones que dan origen a esta tesis y que nos han permitido concluir que: 1) la cirugía debe seguir siendo el tratamiento de elección para los aneurismas de ACM; 2) las técnicas no convencionales como el flash de fluorescencia, el clipaje contralateral y las opciones de bypass intracraneal amplían las posibilidades de tratar con éxito aneurismas complejos y; 3) los resultados quirúrgicos de esta revisión pueden servir como referente de los resultados a los que debe aspirar la terapia endovascular. Aneurismas ACM A. Rodríguez-Hernández 18 ABSTRACT The treatment of cerebral aneurysms has radically changed since the publication of the International_Subarachnoid_Aneurysm_Trial (ISAT), which led to the widespread adoption of a pro-embolization policy in which surgery is reserved only for those cases in which endovascular treatment fails. However, this new therapeutic algorithm has raised controversy and serious concerns about its scientific validity. The management of middle cerebral artery (MCA) aneurysms, one of the most frequent locations of intracranial aneurysms, has been questioned and confused by these changes in aneurysm practice. These aneurysms have long been considered unfavorable for endovascular treatment and, conversely, favorable and easily accessible for microsurgical options. Also, microsurgical techniques have significantly advance in recent years, granting an even safer and more effective treatment of complex MCA aneurysms. This manuscript investigates the hypothesis that MCA aneurysms remain an example of intracranial aneurysms where surgical treatment is currently superior to the available endovascular options. The prospective database of the Neurosurgical Vascular Service at the University of California (San Francisco) was reviewed. During a 13 years period, 2455 intracranial aneurysms were microsurgically managed at the institution and 631 of them were MCA aneurysms. Clinical and radiological results of conventional clipping and new developments in microsurgical techniques were analyzed and compared with the results of previous surgical and endovascular series that were identified through a systematic review of the literature. The results have been published through the four manuscripts that integrate this thesis project and allowed us to conclude that: 1) Surgery should remain the treatment of choice for MCA aneurysms; 2) Non-conventional microsurgical techniques such as flash-fluorescence, contralateral clipping and intracranial bypass options expand the possibilities of successfully treating complex MCA aneurysms and; 3) Surgical Results from our experience set a benchmark that endovascular results should match before being considered an alternative. Aneurismas ACM A. Rodríguez-Hernández 19 II.- Introducción Aneurismas ACM A. Rodríguez-Hernández 20 Aneurismas ACM A. Rodríguez-Hernández 21 II.- INTRODUCCION 1.- Epidemiología Los aneurismas cerebrales consisten en una dilatación patológica de la pared arterial que puede ir aumentando progresivamente de tamaño causando síntomas neurológicos por efecto de masa o llegando a romperse provocando una hemorragia intracraneal generalmente de distribución subaracnoidea. Se estima que la incidencia global de hemorragia subaracnoidea (HSA) de origen aneurismático es de aproximadamente unos 9 casos/100000 habitantes año, aunque varía de forma importante entre diferentes países, como en el caso de la población japonesa y finlandesa donde la incidencia ronda los 20 casos/100.000 hab/ año (37, 61, 74, 87, 122). En nuestro país, aunque no existen datos generales, se estima que la incidencia de HSA es algo menor que la media y ronda los 5-6 casos/100000 habitantes (23, 77). La HSA aneurismática es un problema de salud importante. Un 12% de los pacientes que sufren una HSA fallecen antes de poder recibir ningún tipo de atención médica (139). De los que consiguen llegar al hospital y recibir tratamiento, la mortalidad se estima entre un 27-44% (44, 60, 74, 76, 102, 133, 162). Entre aquellos que sobreviven, menos del 50% vuelven a su estado funcional previo al sangrado a pesar de los avances en el tratamiento (44, 62, 69, 78, 133). Además, los pacientes afectados por una HSA son relativamente jóvenes, con una edad media de 50 años (69). Sin embargo, un porcentaje no desdeñable de los aneurismas intracraneales son asintomáticos (se estima que solo 1 de cada 200-400 aneurismas intracraneales llegaría a romperse a lo largo de la vida del individuo; (157)) por lo que su incidencia real en la población es difícil de concretar. En los últimos años, los avances en las técnicas de neuroimagen no invasiva y su amplia disponibilidad están contribuyendo a aportar cada vez más datos sobre la epidemiología y la historia natural de estas lesiones (4, 157). Por el momento, según los datos procedentes de series de autopsias y de estudios angiográficos, se estima que la prevalencia de Aneurismas ACM A. Rodríguez-Hernández 22 aneurismas intracraneales en la población adulta podría variar entre un 1-5%, siendo menor hasta la segunda década de la vida y aumentando de forma constante a partir de la tercera (3, 60, 91, 123, 157, 160). La arteria cerebral media es una de las localizaciones más habituales de aneurismas intracraneales tanto rotos como no rotos, representando entre un 21-40% de los casos dependiendo de las series consultadas (33, 77, 124). En nuestro medio, según la base multicéntrica de hemorragia subaracnoidea (HSA) gestionada por el grupo de trabajo de Patología Vascular de la Sociedad Española de Neurocirugía, los aneurismas de la ACM son responsables del 21% de las HSA (77). 2.- Etiología Salvo en raras excepciones (95, 150), los aneurismas cerebrales no están presentes en el momento del nacimiento ni en la primera infancia, si no que constituyen una patología que se adquiere a lo largo de la vida. Es probable que los aneurismas cerebrales se formen a partir de un complejo conjunto multifactorial de circunstancias que incluirían una predisposición anatómica congénita potenciada por factores ambientales locales o sistémicos que debilitan aún más la pared arterial y conducen a la formación de la dilatación aneurismática. Sekhar y Heros resumen los datos histológicos disponibles y apuntan a un número de factores congénitos implicados en la formación de aneurismas: defectos en la media, defectos en la elástica, punto de origen de vasos pequeños y fallo involutivo de ramas arteriales (140). El componente genético de estos factores puede ser hereditario en algunos casos, explicando así el 10% de aneurismas familiares (70, 131, 170). Otros factores etiológicos adquiridos como los cambios degenerativos, adelgazamiento de la íntima, inflamación, ateroesclerosis, hipertensión y stress hemodinámico jugarían también un papel importante (140). El tabaco y algunas drogas como la cocaína también se asocian a una mayor incidencia de aneurismas cerebrales y, por Aneurismas ACM A. Rodríguez-Hernández 23 tanto, se les supone un papel etiológico en la formación de los mismos. El hecho de que la incidencia de aneurismas sea mayor en mujeres hace suponer también la implicación etiológica, aún no completamente definida, de los estrógenos. Algo menos de un 10% de los aneurismas intracraneales se dan en pacientes afectos de otras patologías sistémicas como la poliquistosis renal, el lupus eritematoso sistémico, el Ehlers-Danhlos tipo IV, el síndrome de Marfan y otras patologías con afectación sistémica vascular o a nivel del tejido conectivo (13, 46, 88, 157, 158, 161). En aquellos aneurismas localizados en bifurcaciones arteriales los factores hemodinámicos parecen tener un papel fundamental en su formación (8, 93, 94, 142, 156). En el ápex de las bifurcaciones, la pared arterial está sometida al impacto directo del flujo sanguíneo y por tanto al mayor stress hemodinámico, lo que favorece la alta frecuencia de aneurismas en las mismas. Aproximadamente el 80-85% de los aneurismas de ACM se localizan en la bifurcación del segmento M1 de la arteria (33, 58, 124, 175) y habitualmente se dirigen lateralmente, en la dirección del eje longitudinal del segmento prebifurcación del tronco principal. Es decir, se originan en la dirección de máxima fuerza hemodinámica, en aquella que el chorro de sangre hubiese seguido de no existir la curva de la bifurcación arterial. Además, varios autores han demostrado la relación entre la geometría de la bifurcación de la ACM y la presencia o no de aneurismas (17, 63, 134), lo que aportaría más argumentos a favor del importante papel de los factores hemodinámicos en la formación de los aneurismas de ACM. Ocasionalmente los aneurismas también se pueden originar cerca de la salida de arterias lenticuloestriadas grandes o ramas corticales tempranas del segmento M1 o en los puntos de ramificación principal del segmento M2. Los aneurismas más distales son bastante raros y generalmente tienen una etiología inflamatoria (130). Aneurismas ACM A. Rodríguez-Hernández 24 3.- Presentación Clínica Similar al resto de aneurismas intracraneales, los aneurismas de la ACM pueden presentarse tras una ruptura aguda en forma habitualmente de hemorragia subaracnoidea. Antes de que lleguen a romperse, pueden presentarse con síntomas neurológicos por efecto de masa, isquemia transitoria, crisis epilépticas, etc. También se diagnostican frecuentemente de forma incidental durante el estudio de alguna otra patología no relacionada. La hemorragia subaracnoidea se presenta típicamente como una cefalea muy intensa y repentina que la mayoría de los pacientes describe de forma característica como la peor cefalea que han tenido en su vida. Se puede acompañar de naúseas, vómitos, meningismo, fotofobia, déficit neurológico, disminución del nivel de conciencia e incluso éxitus. Hasta en un 20% de los casos, y especialmente en aquellos asociados a aneurismas de la ACM, se pueden producir también crisis epilépticas en las primeras 24h tras la HSA (31). Desde un 15 hasta un 37% de los pacientes que sufren una HSA presentan cefaleas menos intensas en los días previos (11, 50, 65). Estas cefaleas se atribuyen a hemorragias centinela del aneurisma (50) y algunos estudios señalan que multiplican por 10 el riesgo de resangrado precoz (12) Como veremos en detalle más adelante, el recorrido de los segmentos más proximales de la ACM transcurre por la cisura de Silvio, completamente rodeada de cerebro. Por este motivo, los aneurismas de ACM frecuentemente se “incrustan” en el parénquima cerebral según crecen y, consecuentemente, cuando se rompen se presentan también de forma habitual con un hematoma intraparenquimatoso asociado a la HSA. Algunos autores encuentran hematomas intraparenquimatosos asociados hasta en el 45-50% de las HSA por aneurisma de ACM (10, 33, 124). La particular propensidad de los aneurismas de ACM a presentar signos focales como hemiparesia o crisis comiciales parciales, se explica también (al menos parcialmente) por esta tendencia a sangrar en el parénquima cerebral. Los hematomas intraparenquimatosos tienden a Aneurismas ACM A. Rodríguez-Hernández 25 afectar principalmente al lóbulo temporal (hasta en el 85% de los casos según Dashti et al. (33)) y al frontal, y con menos frecuencia se extienden hacia los ganglios de la base. Los aneurismas no rotos se diagnostican frecuentemente de forma incidental durante el estudio de una HSA por otro aneurisma en distinta localización o durante el estudio de otras patologías no relacionadas con el aneurisma (161). Los aneurismas de ACM son los que más frecuentemente se encuentran de forma casual (157) y se etiquetan como asintomáticos. Algunos autores estiman que hasta un 60% de los aneurismas de ACM se diagnostican de forma incidental (14). Pero los aneurismas no rotos, especialmente los de mayor tamaño, también pueden presentarse con todo tipo de síntomas que incluyen cefaleas, afectación de pares craneales, efecto de masa, déficit motor y/o sensitivo, crisis epilépticas, episodios isquémicos, etc. 4.- Diagnóstico y Evaluación Preoperatoria La angiografía cerebral con sustracción digital (ASD) continúa siendo a día de hoy el “gold standard” para el diagnóstico y el estudio anatómico de los aneurismas cerebrales. Aporta la mayor sensibilidad para el diagnóstico de aneurismas de menos de 3mm de diámetro y la mejor resolución de imagen para los vasos de menor calibre como son las arterias perforantes (32, 92, 179). La reconstrucción de las imágenes en 3D nos permite analizar todo el recorrido de la ACM en la cisura de Silvio, la longitud y profundidad de los distintos segmentos arteriales, el tamaño, morfología y proyección del aneurisma y su relación con las ramas arteriales adyacentes. Estas imágenes se pueden rotar para simular la visión que tendríamos en el campo quirúrgico, lo cual facilita la planificación tanto de la estrategia de disección como de clipaje del aneurisma (75, 174). A pesar de todas las ventajas enumeradas, la ASD no deja de ser una prueba invasiva que comporta cierto riesgo de complicaciones que aunque no llegan al 1% de los casos, incluyen infarto cerebral, daño arterial e incluso rotura del aneurisma entre otras (28, 157). Aneurismas ACM A. Rodríguez-Hernández 32 Craneotomía La gran mayoría de aneurismas de la ACM se pueden resolver con una craneotomía fronto-temporal o pterional clásica iniciada con uno o varios agujeros de trépano. La localización más habitual para los agujeros de trépano es temporal y pterional (“key hole”), aunque se han descrito múltiples variaciones a esta técnica (14, 33, 52, 53, 175). La parte posterior de la craneotomía clásica sigue la línea temporal de la incisión de piel y una vez superada la línea temporal superior, se curva hacia delante siguiendo una dirección anterior para terminar medial al foramen del nervio supraorbitario. Desde ahí se curva hacia abajo siguiendo la dirección de la fosa craneal anterior hasta llegar al pterion, que impedirá el paso del craneotomo. La craneotomía se completa subiendo el craneotomo desde el trépano temporal hacia el pterion y fresando o partiendo la porción de hueso que queda sobre este. El pterion es la estructura tridimensional que constituye la unión del hueso frontal, el hueso parietal y el ala mayor del esfenoides. Se puede localizar en la superficie gracias a la intersección de la sutura coronal con el ala mayor del esfenoides. Su estructura interna es tridimensional, lo que impide cortarlo directamente con el craneotomo requiriendo gubias y fresado para su exéresis. El objetivo es fresar el pterion y el ala menor del esfenoides medialmente a la cisura orbitaria superior para aplanar la superficie que conecta la fosa craneal anterior con la fosa media y permitir así, una vez abierta la dura, una visión completa y libre de obstáculos de la cisterna carotidea. Una vez completada la craneotomía y el fresado del pterion, se abre la dura con una incisión semicircular desde el suelo de la fosa media hasta el suelo de la fosa craneal anterior y se retrae el colgajo sobre el pterion mediante suturas que lo mantengan fuera del ángulo de visión que queremos obtener hacia la cisterna carotidea. Aneurismas ACM A. Rodríguez-Hernández 33 Figura 3.- Visión de la cisura de Silvio y las cisternas óptica y carotídea una vez realizada una craneotomía pterional izquierda y la apertura dural. Disección intracraneal La craneotomía pterional permite dos tipos de abordaje microquirúrgico a los aneurismas de ACM: transilviano o subaracnoideo (disecando la cisura de Silvio para llegar a la lesión) y transcortical o subpial (a través del girus temporal superficial). a) Abordaje subaracnoideo o transilviano La cisura de Silvio constituye una puerta de entrada natural hacia cualquier aneurisma localizado en el polígono de Willis. Su disección permite separar el lóbulo frontal del lóbulo temporal, abriendo así un pasillo de acceso hacia las cisternas arteriales de la base craneal. La apertura inicial se realiza con un microbisturí de entre 20-23G o con pinzas de relojero. La disección subaracnoidea progresa cortando la aracnoides con microtijeras, separando suavemente los planos con ayuda de la punta del aspirador, inyectando suero salino en el espacio subaracnoideo y abriendo y cerrando las puntas de la pinza bipolar una vez alineadas en paralelo con las arterias y las superficies piales. Se pueden utilizar lentinas para Aneurismas ACM A. Rodríguez-Hernández 34 mantener el espacio subaracnoideo abierto y para controlar algún pequeño sangrado venoso. Es importante preservar en todo momento el plano pial para evitar edema y contusiones postquirúrgicas. La cisura de Silvio se puede disecar de distal a proximal (o de lateral a medial), abriendo primero la porción más lateral de la cisura y trazando las ramas corticales de la ACM hacia la bifurcación. Este abordaje minimiza la retracción y, por tanto, las posibilidades de dañar tejido cerebral, las ramas de la ACM y sus perforantes. Sin embargo, una disección de distal a proximal aborda los aneurismas de la ACM sin tener control vascular proximal, lo cual no debería suponer mayor problema con los aneurismas no rotos pero puede resultar peligroso con aneurismas que han sangrado. En los casos de aneurismas rotos se puede iniciar la apertura distalmente para establecer los planos de disección subaracnoidea y a continuación cambiar a disección proximal para tener control vascular. En la disección de proximal a distal (o de medial a lateral), se retrae el lóbulo frontal exponiendo el nervio óptico y la carótida. Se abre la cisterna carotídea y desde ahí se diseca distalmente siguiendo el segmento M1 de la ACM hacia la cisura de Silvio. Este abordaje permite la exposición y control de la ACM antes de exponer el aneurisma, pero suele requerir el uso de retractores. Además, la disección proximal produce a liberación precoz de LCR puede colapsar aún más una cisura ya de por sí difícil de disecar en los casos de HSA. b) Abordaje transcortical o subpial A través de una incisión en el girus temporal superficial y una posterior disección subpial, se expone la ACM, sus ramas y el cuello del aneurisma. Este abordaje inicialmente descrito por Heros (54), reduce la retracción cerebral y disminuye la manipulación de la ACM y sus ramas. Sin embargo, cabe la posibilidad de encontrarse la cúpula del aneurisma primero. Y, dada la incisión cortical, el riesgo de epilepsia postquirúrgica es mayor. Aneurismas ACM A. Rodríguez-Hernández 35 Clipaje Una vez expuesto el aneurisma, podemos emplear diferentes técnicas de clipaje (un clip simple, múltiples clips, clips en tándem, etc) para su oclusión. La colocación del o los clips debe cerrar el cuello sin dejar remanentes y conseguir al mismo tiempo preservar el flujo normal en el segmento arterial que da origen al aneurisma. Un solo clip puede ocluir con facilidad un aneurisma pequeño, de morfología simple y cuello estrecho (Figura 4A). Sin embargo, un alto porcentaje de aneurismas de ACM, especialmente los localizados en la bifurcación, presentan un cuello ancho y una morfología irregular que a veces incluye una o ambas ramas de la bifuración. Los cuellos complejos se pueden descomponer en partes más sencillas que se van clipando progresivamente hasta conseguir la oclusión completa. Por ejemplo, en un aneurisma de cuello ancho podemos colocar un primer clip que cierre la porción más distal y profunda del cuello y, a continuación, ir colocando clips por encima hasta llegar a la porción más proximal y conseguir el cierre completo (Figura 4B). Las porciones del cuello que presenten ateroesclerosis o calcificaciones, se pueden evitar mediante la aplicación de un clip fenestrado que salve dicha porción más un clip menor que cierre la fenestración del anterior. Los aneurismas parcialmente trombosados se pueden abrir por completo para extraer parte del material trombótico y reconstruir posteriormente toda la cúpula con clips. Figura 4.- Ejemplos de distintas técnicas de clipaje Aneurismas ACM A. Rodríguez-Hernández 36 Independientemente de la técnica empleada, una vez clipado el aneurisma, se debe comprobar la correcta permeabilidad de las ramas circundantes mediante inspección microscópica directa y mediante doppler, videoangiografía intraoperatoria con verde de indocianina y/o angiografía convencional (36, 82). B.-Tratamiento Endovascular Anestesia El tratamiento endovascular o embolización se puede realizar bajo sedación consciente o bajo anestesia general. En un paciente con comorbilidades importantes, la sedación evita la intubación traqueal y permite la comprobación constante de la exploración neurológica durante el procedimiento. Tiene la desventaja de producir artefactos de movimiento en la imagen y, además, no es una buena opción en aquellos pacientes con algún grado de confusión o que no cooperan adecuadamente. La anestesia general permite un mejor control de la tensión arterial y la oxigenación y ayuda a reducir los artefactos por movimiento. Las desventajas incluyen la imposibilidad de realizar exámenes neurológicos y el riesgo de hipotensión sistémica (68, 83, 165). Cateterización Vascular La arteria femoral derecha en su segmento proximal a la bifurcación y distal a la salida de la arteria epigástrica, es habitualmente el vaso de elección para el acceso endovascular. Una vez localizada en la ingle aproximadamente sobre la cabeza del fémur, se cateteriza con un catéter guía unido a una irrigación continúa de salino y heparina para evitar complicaciones tromboémbolicas. En los aneurismas no rotos, se puede administrar un bolo inicial de 70-100 UI/kg; en los rotos, algunos autores prefieren esperar hasta que la cúpula del aneurisma esté ya protegida con coils para evitar un resangrado con la infusión del bolo de heparina (38). Habitualmente la anticoagulación con heparina se revierte al final del procedimiento salvo que Aneurismas ACM A. Rodríguez-Hernández 37 se haya producido alguna complicación tromboembólica o salvo que se sospeche que los coils pudieran protruir por fuera del cuello aneurismático (35). Una vez avanzado el catéter guía hasta la carótida interna, se debe realizar una primera imagen general de la circulación intracraneal para obtener una imagen inicial del aneurisma y detectar posibles estenosis, áreas de vasoespasmo o émbolos que requieran tratamiento antes de continuar avanzando el catéter. Microcateterización del aneurisma Se puede realizar de forma directa introduciendo la microguía en el aneurisma y pasando el microcatéter a través de ella, o de forma indirecta, pasando incialmente tanto la microguía como el microcatéter más allá del cuello del aneurisma, hacia la arteria distal y entrando en el cuello aneurismático con una maniobra de retirada. Embolización del saco aneurismático Una vez situado el microcatéter en el aneurisma, se puede comenzar a subir y liberar los coils. Habitualmente, el primer coil debe ser del tamaño del aneurisma o ligeramente inferior en el caso de aneurismas rotos (para evitar un resangrado). Después se deben ir liberando coils de forma progresiva hasta conseguir una oclusión completa del aneurisma. Entre la colocación de cada coil y al final del procedimiento, se debe realizar una imagen angiográfica para comprobar la correcta posición del coil, la porción de aneurisma que aún permanece permeable (o la oclusión completa si estamos al final del procedimiento), la ausencia de extravasación de contraste (que indicaría una ruptura) y la ausencia de complicaciones tromboembólicas. Embolización con stent y embolización con balón Para evitar que los coils se hernien desde el aneurisma a la arteria de origen, se pueden usar dos técnicas: Aneurismas ACM A. Rodríguez-Hernández 38 1.- Embolización asistida con stent: consiste en colocar un stent en la rama que da origen al aneurisma de tal forma que dicho stent cubra de un lado al otro del cuello. En los aneurismas de la bifurcación de ACM, esta técnica requerirá de dos stents en “Y” colocados desde la porción prebifurcación y hacia cada una de las ramas distales. La embolización asistida con stent se puede realizar accediendo con un microcatéter al saco aneurismático a través del stent. Sin embargo, puede ser complicado pasar el microcatéter a través de la red del stent. Una alternativa para evitar este problema es la técnica conocida como “jailing” o “enjaulado” que consiste en introducir primero un microcatéter en el aneurisma y liberar a continuación el stent con un segundo microcatéter, evitando así tener que acceder a través del stent. 2.- Embolización asistida con balón: una vez introducido el microcatéter en el aneurisma, se coloca e infla un balón de un lado a otro del cuello para evitar que los coils se hernien hacia la arteria. Una vez terminada la embolización, el balón se desinfla y se retira. La embolización asistida con stent tiene la ventaja de dejar de forma permanente el stent como soporte de la masa de coils, sin embargo requiere el uso prolongado de antiagregantes (motivo por el cual no se recomienda usar en aneurismas rotos) y presenta complicaciones a largo plazo por estenosis del stent. El balón evita el uso de antiagregantes y las posibles complicaciones de estenosis a largo plazo. Sin embargo puede provocar isquemia en el territorio distal a su colocación. Por este motivo, requiere el inflado y desinflado periódico durante el proceso de embolización, con el consiguiente riesgo de rotura arterial cada vez que el balón se infla de nuevo. Algunos estudios (167, 168) señalan una mayor tasa de repermeabilización en los aneurismas embolizados con asistencia de balón. Flow diverters Los dispositivos de desviación de flujo o “flow diverters” consisten en stents con una doble malla metálica trenzada que ofrece una cobertura hasta tres veces mayor que la de los Aneurismas ACM A. Rodríguez-Hernández 39 stents previos y cuyo mecanismo de acción consistiría, principalmente, en disminuir la entrada de flujo sanguíneo en el aneurisma redirigiendo dicho flujo a través del cuello. Inicialmente su uso se aprobó para aneurismas gigantes o de cuello ancho (más de 4mm) de la carótida interna en los que el tratamiento quirúrgico y/o la embolización no ofrecían resultados completamente satisfactorios (38). Sin embargo, al ir aumentado la experiencia clínica con estos dipositivos, su uso se ha ido ampliando a otros aneurismas incluyendo incluso los localizados en bifurcaciones arteriales como sería el caso de los aneurismas de ACM (15, 18, 19, 20, 24, 89, 177). Hasta la fecha, no se han completado estudios prospectivos randomizados que comparen la eficacia y los riesgos y beneficios de los stents desviadores de flujo frente a la embolización simple o el clipaje. Existe al menos un estudio multicéntrico que previsiblemente se completará en 2017 (118). Hasta entonces, la ausencia de pruebas sólidas sobre la seguridad (especialmente a largo plazo) de estos dispositivos, aboga por estudiar cada caso detenidamente y hacer un uso prudente de esta tecnología (7, 30). En particular, en los aneurismas localizados en las bifurcaciones, el uso de desviadores de flujo se ha asociado a graves complicaciones que en principio deberían contraindicar su uso (89). Embolización con dispositivo WEB El WEB (“Woven Endobridge Device”; Sequent Medical, Inc.,Aliso Viejo, CA, USA) consiste en un dispositivo auto-expandible de red metálica trenzada con forma de esfera achatada por los polos, diseñado para actuar como un derivador de flujo pero que se libera dentro del saco aneurismático (72). Su uso requiere un estudio detallado de la morfología, diámetro, altura y tamaño del cuello del aneurisma a tratar para poder elegir el tamaño adecuado del dispositivo WEB. Se recomienda elegir un dispositivo 1 mm mayor que el diámetro medio del aneurisma y 1 mm Aneurismas ACM A. Rodríguez-Hernández 40 menor que la altura media del mismo (111). Una vez posicionado el catéter guía, la cateterización del aneurisma requiere un microcateter de tamaño bastante mayor (27 French) a los utilizados para embolización con coils. Una vez colocado el dispositivo en el aneurisma, se realiza una imagen de control. Si el tamaño o la posición no son los adecuados, se recalienta el dispositivo para poder modificar su posición o para retirarlo y colocar uno nuevo de tamaño más adecuado. A pesar de la ausencia de datos clínicos al respecto, algunos autores defienden que el uso del dispositivo WEB se puede asociar al uso de stents clásicos y coils si se estima necesario (111). La tasa de complicaciones tromboémbolicas con este tipo de dispositivo ronda el 16% de los casos, por lo que sería mayor que la descrita para otro tipo de tratamientos endovasculares (110, 111, 112). Además, no está claramente relacionada con el uso o no de antiagregantes ni con la dosis o tipo de fármaco empleado. Las series clínicas de experiencia preliminar con este dispositivo para aneurismas de ACM, describen una oclusión completa en menos del 30% de los casos tratados (111). C.- Observación En los últimos años parece haberse incrementado el porcentaje de aneurismas de ACM diagnosticados de forma incidental antes de que pudieran romperse. Es en estos casos diagnosticados de forma incidental en los que podría plantearse el dilema de tratar o no, ya que parece que solo una minoría de estos aneurismas acabarían rompiéndose y ya que cualquier opción de tratamiento tiene cierto riesgo de morbilidad e incluso mortalidad (13, 22, 25, 51). Si nos guiamos por los resultados del estudio internacional de aneurismas intracraneales no rotos (161), solo debería plantearse tratamiento de los aneurismas de ACM en pacientes asintomáticos cuando el saco aneurismático supere los 7mm de diámetro máximo, ya que por debajo de dicho umbral el riesgo de rotura sería prácticamente desdeñable. Por lo tanto, en pacientes con un aneurisma por debajo del citado tamaño, sería razonable ofrecerles Aneurismas ACM A. Rodríguez-Hernández 41 observación clínico-radiológica como la opción de elección para el manejo de su patología. Sin embargo, algunos autores señalan que hasta en un 29% de los casos de aneurismas de ACM rotos, el saco aneurismático tenía un diámetro menor de 8mm, lo cual sugiere que los aneurismas pequeños también pueden ser peligrosos y cuestiona los resultados del estudio ISUIA y los algoritmos de manejo derivados del mismo (33, 42). Además, aunque el riesgo de rotura en determinados casos sea pequeño, las consecuencias de una posible HSA son devastadoras en un alto porcentaje de pacientes que desgraciadamente suelen ser relativamente jóvenes (16). 7.- Selección Opciones de Tratamiento: Justificación del Estudio El tratamiento de los aneurismas cerebrales ha cambiado radicalmente desde la publicación en 2002 del ISAT (“International Subarachnoid Aneurysm Trial”, (96)), que provocó la adopción generalizada de una política pro-embolización en la que todos los aneurismas se consideran inicialmente para tratamiento endovascular y se reserva la cirugía solo para aquellos que presentan una anatomía desfavorable o en los que fallan los intentos de embolización (29). Sin embargo, este algoritmo terapéutico que parece haberse implantado ampliamente gracias al ISAT, es foco de importantes controversias y numerosos autores plantean serias dudas sobre el mismo (2, 9, 117) . En primer lugar, aunque el ISAT se limitaba a analizar un pequeño grupo de pacientes con aneurismas rotos (de los 9559 pacientes posibles solo se incluyeron 2143, un 22.4%), los resultados han sido extrapolados para justificar el tratamiento endovascular tanto de aneurismas rotos como no rotos y en cualquier localización intracraneal. Por ejemplo, hay una tendencia a asumir que el tratamiento endovascular de los aneurismas de la bifurcación basilar es mejor que la cirugía y, de hecho, es la única opción terapéutica que se ofrece para estos aneurismas en muchos centros, a pesar de que el ISAT solo incluyó 26 pacientes (1.2%) de este tipo. En segundo lugar, las ventajas del tratamiento endovascular sobre el quirúrgico desaparecen a partir de los 3-5 años de seguimiento debido a las recurrencias, resangrados y morbid- Aneurismas ACM A. Rodríguez-Hernández 48 Aneurismas ACM A. Rodríguez-Hernández 49 IV.- MATERIAL y MÉTODOS Se revisa la base de datos prospectiva del Servicio de Neurocirugía Vascular de la Universidad de California (San Francisco), una institución de reconocido prestigio en este ámbito y que mantiene una política de ofertar la cirugía como tratamiento de primera línea de los aneurismas de ACM. Durante un periodo de 13 años comprendido desde Septiembre de 1997 hasta Marzo de 2010, un total de 2455 aneurismas fueron tratados con microcirugía en 1913 pacientes. De estos pacientes, 543 (28,4% del total de pacientes) presentaron 631 aneurismas de ACM (25,7% del total de aneurismas). Había 406 mujeres (75%) y 137 hombres (25%), con una edad media de 55,3 años (rango, 1 – 87 años). La exclusión de los aneurismas se evaluó de forma independiente por un neurorradiólogo que clasificó los resultados como oclusión completa (sin aneurisma residual), mínimo aneurisma residual (mínimo resto de cuello) u oclusión incompleta (resto de más del 5% del aneurisma inicial). Los resultados neurológicos se evaluaron mediante la escala modificada de Rankin. Una enfermera o un neurólogo no involucrados directamente en la atención del paciente y no pertenecientes al Servicio de Neurocirugía, realizaron estas evaluaciones clínicas de forma preoperatoria, postoperatoria precoz y a lo largo de todo el período de seguimiento disponible. El análisis estadístico de las variables categóricas se realizó utilizando la Chi cuadrado, corrigiendo mediante Bonferroni para comparaciones múltiples y estableciendo una p<0.05 como criterio de significación estadística en el análisis univariante. Se utilizó el programa Stata 12 para dicho análisis. Para comparar los resultados con otras series de tratamiento quirúrgico y endovascular, se realizó una revisión de la literatura en PubMed y Medline utilizando como palabras clave y Aneurismas ACM A. Rodríguez-Hernández 50 como texto libre: “middle cerebral artery aneurysms” ó “MCA aneurysms” y “treatment” ó “management”. Se limitó la búsqueda a artículos en inglés y español publicados a partir de enero de 1984 y hasta enero de 2012. Inicialmente se revisó el resumen de los artículos identificados y posteriormente se obtuvo el texto completo de aquellos potencialmente relevantes. Las referencias de cada artículo incluido se revisaron también para buscar artículos adicionales. Aneurismas ACM A. Rodríguez-Hernández 51 V.- Resultados Aneurismas ACM A. Rodríguez-Hernández 52 Aneurismas ACM A. Rodríguez-Hernández 53 V.- RESULTADOS La tesis se basa en los resultados de las siguientes publicaciones originales: 1. Current management of middle cerebral artery aneurysms: surgical results with a “clip first” policy. Rodríguez-Hernández A, Sughrue ME, Akhavan S, Habdank-Kolaczkowski J, Lawton MT. Neurosurgery 72:415–427, 2013. 2. Flash fluorescence with indocyanine green videoangiography to identify the recipient artery for bypass with distal middle cerebral artery aneurysms: operative technique. RodríguezHernández A, Lawton MT. Neurosurgery 70:ons209–220, 2012. 3. Contralateral Clipping of Middle Cerebral Artery Aneurysms: Rationale, Indications, and Surgical Technique. Rodríguez-Hernández A, Gabarrós A, Lawton MT. Neurosurgery, 71:ons116-123, 2012. 4. End-to-End Reanastomosis Technique for Fusiform Aneurysms: 3D Operative Video. Rodríguez-Hernández A, Lawton MT. Neurosurgery 10:157-158, 2014. Aneurismas ACM A. Rodríguez-Hernández 54 Aneurismas ACM A. Rodríguez-Hernández 55 1er Artículo Aneurismas ACM A. Rodríguez-Hernández 56 Aneurismas ACM A. Rodríguez-Hernández 57 Current Management of Middle Cerebral Artery Aneurysms: Surgical Results With a “Clip First”Policy BACKGROUND: One response to randomized trials like the International Subarachnoid Aneurysm Trial has been to adopt a “coil first” policy, whereby all aneurysms be considered for coiling, reserving surgery for unfavorable aneurysms or failed attempts. Surgical results with middle cerebral artery (MCA) aneurysms have been excellent, raising debate about the respective roles of surgical and endovascular therapy. OBJECTIVE: To review our experience with MCA aneurysms managed with microsurgery as the treatment of first choice. METHODS: Five hundred forty-three patients with 631 MCA aneurysms were managed with a “clip first” policy, with 115 patients (21.2%) referred from the Neurointerventional Radiology service and none referred from the Neurosurgical service for endovascular management. RESULTS: Two hundred eighty-two patients (51.9%) had ruptured aneurysms and 261 (48.1%) had unruptured aneurysms. MCA aneurysms were treated with clipping (88.6%), thrombectomy/clip reconstruction (6.2%), and bypass/aneurysm occlusion (3.3%). Complete aneurysm obliteration was achieved with 620 MCA aneurysms (98.3%); 89.7% of patients were improved or unchanged after therapy, with a mortality rate of 5.3% and a permanent morbidity rate of 4.6%. Good outcomes were observed in 92.0% of patients with unruptured and 70.2% with ruptured aneurysms. Worse outcomes were associated with rupture (P= .04), poor grade (P= .001), giant size (P= .03), and hemicraniectomy (P,.001). CONCLUSION: At present, surgery should remain the treatment of choice for MCA aneurysms. Surgical morbidity was low, and poor outcomes were due to an inclusive policy that aggressively managed poor-grade patients and complex aneurysms. This experience sets a benchmark that endovascular results should match before considering endovascular therapy an alternative for MCA aneurysms. KEY WORDS: Bypass, Clip first policy, Clipping, Microsurgery, Middle cerebral artery aneurysms Neurosurgery 72:415–427, 2013 DOI: 10.1227/NEU.0b013e3182804aa2 www.neurosurgery-online.com The International Subarachnoid Aneurysm Trial (ISAT) changed the management of brain aneurysms in developed countries, 1,2 legitimizing endovascular coiling as a safe alternative to surgical clipping and supplanting clipping as the aneurysm treatment of choice for many aneurysms at many centers. The Barrow Ruptured Aneurysm Trial reinforced many of the results from the ISAT and eliminated the criticism that American surgeons with more aneurysm experience would have better microsurgical results. 3 One response to these randomized trials has been the adoption of a“coil first”policy, whereby all aneurysms be considered for coiling, reserving surgery for those with unfavorable anatomy or failed coiling attempts. 4 This management policy raises serious concerns. First, although the ISAT examined a small subset of eligible patients with ruptured aneurysms (2143/9559, 22.4%), the results have been Ana Rodr ıguez-Herna ´ndez, MD Michael E. Sughrue, MD Sina Akhavan, BS Julian Habdank-Kolaczkowski, BS Michael T. Lawton, MD Department of Neurological Surgery, University of California at San Francisco, San Francisco, California Correspondence: Michael T. Lawton, MD, Department of Neurological Surgery, University of California, San Francisco, 505 Parnassus Ave, San Francisco, CA 94143. E-mail: [email protected] Received, April 1, 2012. Accepted, November 26, 2012. Published Online, November 30, 2012. Copyright ª2012 by the Congress of Neurological Surgeons ABBREVIATIONS: ICG, indocyanine green; ISAT, International Subarachnoid Aneurysm Trial; MCA, middle cerebral artery; mRS, modified Rankin score; SAH, with subarachnoid hemorrhage RESEARCH—HUMAN—CLINICAL STUDIES TOPIC RESEARCH—HUMAN—CLINICAL STUDIES NEUROSURGERY VOLUME 72 | NUMBER 3 | MARCH 2013 | 415 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. Aneurismas ACM A. Rodríguez-Hernández 64 less frequently in patients undergoing endovascular therapy than in patients undergoing surgery (3.1% vs 5.7%), but the associated morbidity and mortality was higher (1.1% vs 0%), because there are fewer endovascular options for dealing with this complication. Importantly, Brinjikji et al 23 found an 18.9% rate of aneurysm recurrence, of which 9.6% was deemed major and required retreatment. Many of these factors influenced eligibility in ISAT, which required therapeutic equipoise between clipping and coiling for inclusion. The relatively few patients with MCA aneurysms in the ISAT is an acknowledgment of these difficulties with endovascular therapy. The absolute (6.9%) and relative (22.6%) risk reductions in dependency and death after endovascular coiling were responsible for significant increases in endovascular therapy worldwide. However, subsequent analysis of ISAT data revealed the following: the advantages of coiling over clipping in terms of death and severe disability at 1 year vanished at 5 years (proportion of independent survivors, 83% and 82%, respectively) 5 ; coiled aneurysms had an increased risk of rebleeding 1 ; late retreatment rates are 6.9 times more likely with coiling than with clipping 32 ; coiling incurred higher costs for the initial procedure, subsequent procedures, follow-up angiography, additional late procedures, and associated complications or adverse events 33 ; clipping protected young patients (,40 years) from SAH better than coiling, with only FIGURE 1. A, a 7-year-old boy presented in coma with a subarachnoid hemorrhage from this giant, dolichoectatic M1 MCA aneurysm (digital subtraction angiography, right internal carotid artery injection, anteroposterior view). A right orbitozygomatic-pterional craniotomy and sylvian fissure split exposed the aneurysm (B), but an attempt at clip reconstruction failed to preserve flow in the efferent M1 segment (C). D, the aneurysm was excised, and the proximal and distal M1 segments were reconnected with an interposition radial artery graft sutured end-to-end. Although 2 lenticulostriate arteries were sacrificed, flow to the distal MCA territory was reconstituted (E), as seen on the postoperative angiogram (right internal carotid artery injection, anteroposterior view) (F). Hemicraniectomy helped control intracranial pressure postoperatively, and he recovered with only mild arm weakness. This case demonstrates 1 bypass option that is available when conventional clipping fails with complex aneurysms. MCA, middle cerebral artery. RODRI ´GUEZ-HERNA ´NDEZ ET AL 422 | VOLUME 72 | NUMBER 3 | MARCH 2013 www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. Aneurismas ACM A. Rodríguez-Hernández 65 TABLE 6. Comparison of Endovascular and Surgical Complications Endovascular Surgery Total Ruptured Aneurysms Unruptured Aneurysms Total Ruptured Aneurysms Unruptured Aneurysms Complications n % n % n % n % n % n % Intraprocedural rupture 32/1030 3.1 19/395 4.8 6/364 1.7 31/543 5.7 21/282 7.4 9/261 3.4 Morbidity from rupture 5/1030 0.5 5/395 1.2 0/364 0.0 0/543 0.0 0/282 0.0 0/261 0.0 Mortality from rupture 6/1030 0.6 4/395 1.0 1/364 0.3 0/543 0.0 0/282 0.0 0/261 0.0 Thromboembolism NA NA NA NA NA NA 7/543 1.3 3/282 1.1 4/261 1.5 Morbidity from thromboembolism 33/1030 3.2 11/455 2.4 19/448 4.2 0/543 0.0 0/282 0.0 0/261 0.0 Mortality from thromboembolism 6/1030 0.6 4/455 0.9 1/448 0.2 4/543 0.7 2/282 0.7 2/261 0.8 Early postoperative hemorrhage 6/1030 0.6 6/530 1.1 0/500 0.0 1/543 0.2 1/282 0.4 0/261 0.0 Morbidity from rehemorrhage 2/1030 0.2 2/530 0.4 0/500 0.0 0/543 0.0 0/282 0.0 0/261 0.0 Mortality from rehemorrhage 0/1030 0.0 0/530 0.0 0/500 0.0 1/543 0.2 1/282 0.4 0/261 0.0 Total morbidity/mortality 5.1 5.9 4.7 0.9 1.1 0.8 Complete aneurysm occlusion 887/1076 82.4 244/310 78.7 273/320 82.7 622/631 98.6 282/282 100.0 340/349 97.4 Incomplete aneurysm occlusion 137/1076 12.7 52/310 16.8 43/320 13.0 9/631 1.4 0/282 0.0 9/349 2.6 Failed attempt 52/1076 4.8 14/310 4.5 14/320 4.2 0/631 0.0 0/282 0.0 0/349 0.0 Minor recurrence 70/758 9.3 0/106 0.0 Major recurrence with retreatment 73/758 9.6 0/106 0.0 Endovascular complications were based on the systematic review of Brinjikji et al, and surgical complications were based on the current series of 631 aneurysms in 543 patients. MCA ANEURYSMS NEUROSURGERY VOLUME 72 | NUMBER 3 | MARCH 2013 | 423 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. Aneurismas ACM A. Rodríguez-Hernández 66 small differences in safety 34 ; and clipping resulted in better outcomes in elderly patients with MCA aneurysms (rate of functional independence, 86.7% and 45.5% with clipping and coiling, respectively). 35 These late findings from the ISAT attracted less attention than its initial publication, but are important reminders that the early advantages of endovascular therapy cannot be assumed to last or generalize to all aneurysms. The ISAT was a study of ruptured aneurysms, and class I data favoring coiling over clipping for unruptured aneurysms does not exist. Even with ruptured aneurysms, data favoring coiling over clipping does not exist with certain aneurysms like MCA aneurysms. Limitations and Trends This was not a randomized, controlled trial comparing clipping and coiling of MCA aneurysms, but rather a single-center, singlesurgeon, retrospective review of surgical results only. Even though there was a “clip first”policy on the Vascular Neurosurgical service, patients were treated endovascularly during the study period when referred directly to the Neurointerventional Radiology service, preferred coiling over clipping, and had anatomy favorable for coiling. There were 64 such patients, and these patients were not included in this review because they were outside of the “clip first”policy on the Neurosurgical service. Our study was not designed to determine therapeutic superiority like the ISAT or Barrow Ruptured Aneurysm Trial. Instead, our study was designed to capture the complete picture of MCA aneurysm management from a neurosurgical perspective, including the full spectrum of patients from intact to moribund, with simple and complex aneurysms, both unruptured and ruptured. Inhomogeneity makes our study results more difficult to interpret than a randomized, controlled trial or FIGURE 2. A, a 69-year-old woman with a left MCA aneurysm was initially treated with coiling and her aneurysm recurred 6 months later, as seen on surveillance angiography (digital subtraction angiography, right internal carotid artery injection, anteroposterior view). B, intraoperatively, the aneurysm had a broad neck, diffuse atherosclerosis, neck calcifications, and coil extrusion through the dome. Tandem clipping repaired the neck, with a fenestrated clip around the proximal coils (C), and additional clips to close the proximal neck beneath the coils (D). E, postoperative angiography demonstrated complete aneurysm occlusion with preservation of the M2 branches (right internal carotid artery injection, anteroposterior view). This case demonstrates the difficulty in achieving a complete and durable coil occlusion of a broad neck MCA aneurysm, and the ease of the surgical solution. MCA, middle cerebral artery. RODRI ´GUEZ-HERNA ´NDEZ ET AL 424 | VOLUME 72 | NUMBER 3 | MARCH 2013 www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. Aneurismas ACM A. Rodríguez-Hernández 67 FIGURE 3. A, a 53-year-old woman presented with SAH from a left MCA aneurysm (digital subtraction angiography, left internal carotid artery injection, anteroposterior view). B, the aneurysm was successfully coiled, but compacted 6 months later (left internal carotid artery injection, anteroposterior view). The aneurysm was re-treated with an additional coil (C), but this coil migrated out of the aneurysm and lodged in a distal M2 branch, as seen on 12-month surveillance angiography (left internal carotid artery injection, anteroposterior view) (D). Intraoperatively, the inferior trunk arose from the base of the aneurysm (E), and a daughter aneurysm was identified posteriorly (F). This daughter aneurysm can be appreciated as a double density on the initial angiogram (A). The daughter aneurysm (G) and the primary aneurysm (H) were clipped with separate clips. I, postoperative angiography confirmed complete aneurysm occlusion (left internal carotid artery injection, anteroposterior view). This case demonstrates the difficulties in deciphering complex MCA anatomy angiographically, the problem of aneurysm recurrence, and embolic complications associated with endovascular coiling. MCA, middle cerebral artery; SAH, subarachnoid hemorrhage. MCA ANEURYSMS NEUROSURGERY VOLUME 72 | NUMBER 3 | MARCH 2013 | 425 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. Aneurismas ACM A. Rodríguez-Hernández 68 a retrospective review of results with 1 subgroup like unruptured MCA aneurysms. 36 However, 1 clear interpretation is that surgery offered as part of a clip first policy has the versatility to deal with this wide spectrum of patients. Multicenter, multisurgeon randomized controlled trials may not be the best methodology to establish best practices for MCA aneurysms because various patient exclusions and variability between surgeons and institutions blur the results. Although controlled studies facilitate outcome comparisons according to treatment modality, all-inclusive, single-surgeon experiences minimize these variables, reflect a realistic practice, and examine critical management factors. Another clear interpretation of our study is that surgical management can achieve results that can be a benchmark for endovascular therapies as they evolve beyond simple coiling techniques to include stent-assisted coiling, intra-arterial flow diverters, intra-aneurysmal flow diverters, and other novel techniques. We attribute our good results to our application of neurosurgical advancements like retractorless sylvian fissure dissection, 37 bypass techniques, 11,38 ICG angiography, 10 and aggressive management of patients who have subarachnoid hemorrhage in the operating room, intensive care unit, and angiography suite. 39 However, just as multicenter trials introduce confounding variabilities, single-surgeon experiences introduce that individual’s unique skills, judgments, and experience. These qualities vary greatly among surgeons and benchmark results from 1 experience may not generalize to other neurosurgeons or centers. Therefore, neurosurgeons should examine their own results, and local competencies and expertise must be considered when determining management policies at individual institutions. Our results as well as published data on surgical clipping and simple coiling support the clip first policy at our institution and microsurgery generally as the treatment of choice for MCA aneurysms. Advances in endovascular technology will continue to spur attempts to treat MCA aneurysms. Stents or flow diverters may improve results, but the requirement of antiplatelet agents limits their application in patients with ruptured aneurysms. Furthermore, the deployment of flow diverters is technically challenging and their efficacy is unclear. Current results with the Pipeline embolization device are best in the cavernous and paraclinoid internal carotid artery where the parent artery is large and branch arteries are few, and worst in the posterior circulation were there are numerous perforators. MCA aneurysms are similarly associated with multiple branches and lenticulostriate perforators, and results in this region are unknown. Technological and technical advancements in endovascular therapy will inevitably challenge the clip first policy with MCA aneurysms, but must demonstrate results that are equivalent or superior to surgical clipping. For now, the MCA aneurysm stands out as an example of how therapeutic management decisions can be made based on aneurysm location alone. Patients are managed best when they are in specialized centers, receive care from dedicated experts, have all treatment options available to them, and are free to make their own choices. Still, they need clear recommendations from their neurosurgeons and other clinicians. Although recommendations or management policies cannot be mandated, consensus supporting surgical clipping of MCA aneurysms is particularly strong and clinicians should feel comfortable speaking with a clear and consistent voice that favors clipping for MCA aneurysms. CONCLUSION Surgery should remain the treatment of choice for MCA aneurysms, except when there are extenuating comorbidities or overriding patient preferences. Surgical morbidity is low, and the patient outcomes are determined largely by neurological presentation. Poor Hunt-Hess grade is often an indication for endovascular therapy, but patients with MCA aneurysms often benefit from hemicraniectomy and clot evacuation. Conventional clipping will repair most MCA aneurysms, but unconventional techniques like thrombectomy/clip reconstruction and bypass/ aneurysm occlusion are possible with open surgery. Surgical results from our experience set a benchmark that endovascular results should match before considering endovascular therapy as an alternative for these lesions. Disclosure The authors have no personal financial or institutional interest in any of the drugs, materials, or devices described in this article. REFERENCES 1. Molyneux AJ, Kerr RS, Yu LM, et al. International subarachnoid aneurysm trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised comparison of effects on survival, dependency, seizures, rebleeding, subgroups, and aneurysm occlusion. Lancet. 2005;366(9488):809-817. 2. Taha MS, Patel UJ. Clipping versus coiling for ruptured intracranial aneurysms after the international subarachnoid aneurysm trial. United Kingdom experience. Neurosciences (Riyadh). 2009;14(2):118-123. 3. McDougall CG, Spetzler RF, Zabramski JM, et al. The Barrow Ruptured Aneurysm Trial. J Neurosurg. 2012;116(1):135-144. 4. Qureshi AI, Vazquez G, Tariq N, Suri MF, Lakshminarayan K, Lanzino G. Impact of International Subarachnoid Aneurysm Trial results on treatment of ruptured intracranial aneurysms in the United States. Clinical article. J Neurosurg. 2011;114 (3):834-841. 5. Bakker NA, Metzemaekers JD, Groen RJ, Mooij JJ, Van Dijk JM. International subarachnoid aneurysm trial 2009: endovascular coiling of ruptured intracranial aneurysms has no significant advantage over neurosurgical clipping. Neurosurgery. 2010;66(5):961-962. 6. Raper DM, Allan R. International subarachnoid trial in the long run: critical evaluation of the long-term follow-up data from the ISAT trial of clipping vs coiling for ruptured intracranial aneurysms. Neurosurgery. 2010;66(6):1166-1169. 7. van Dijk JM, Groen RJ, Ter Laan M, Jeltema JR, Mooij JJ, Metzemaekers JD. Surgical clipping as the preferred treatment for aneurysms of the middle cerebral artery. Acta Neurochir (Wien). 2011;153(11):2111-2117. 8. Lawton MT, Quinones-Hinojosa A, Sanai N, Malek JY, Dowd CF. Combined microsurgical and endovascular management of complex intracranial aneurysms. Neurosurgery. 2008;62(6 suppl 3):1503-1515. 9. Lawton MT. Selecting therapy for complex aneurysms. World Neurosurg. 2011;75 (3-4):408. 10. Rodr ıguez-Hernández A, Lawton MT. Flash fluorescence with ICG videoangiography to identify the recipient artery for bypass with distal middle cerebral artery aneurysms: operative technique. Neurosurgery. 2012;70(2 suppl operative): 209-220. RODRI ´GUEZ-HERNA ´NDEZ ET AL 426 | VOLUME 72 | NUMBER 3 | MARCH 2013 www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. Aneurismas ACM A. Rodríguez-Hernández 69 11. Sanai N, Zador Z, Lawton MT. Bypass surgery for complex brain aneurysms: an assessment of intracranial-intracranial bypass. Neurosurgery. 2009;65(4):670-683. 12. Sughrue ME, Saloner D, Rayz VL, Lawton MT. Giant intracranial aneurysms: evolution of management in a contemporary surgical series. Neurosurgery. 2011;69 (6):1261-1270. 13. Iijima A, Piotin M, Mounayer C, Spelle L, Weill A, Moret J. Endovascular treatment with coils of 149 middle cerebral artery berry aneurysms. Radiology. 2005;237(2):611-619. 14. Horowitz M, Gupta R, Gologorsky Y, et al. Clinical and anatomic outcomes after endovascular coiling of middle cerebral artery aneurysms: report on 30 treated aneurysms and review of the literature. Surg Neurol. 2006;66(2):167-171. 15. Doerfler A, Wanke I, Goericke SL, et al. Endovascular treatment of middle cerebral artery aneurysms with electrolytically detachable coils. AJNR Am J Neuroradiol. 2006;27(3):513-520. 16. Lubicz B, Graca J, Levivier M, et al. Endovascular treatment of middle cerebral artery aneurysms. Neurocrit Care. 2006;5(2):93-101. 17. Quadros RS, Gallas S, Noudel R, Rousseaux P, Pierot L. Endovascular treatment of middle cerebral artery aneurysms as first option: a single center experience of 92 aneurysms. AJNR Am J Neuroradiol. 2007;28(8):1567-1572. 18. Guglielmi G, Viñuela F, Duckwiler G, Jahan R, Cotroneo E, Gigli R. Endovascular treatment of middle cerebral artery aneurysms. Overall perioperative results. Apropos of 113 cases. Interv Neuroradiol. 2008;14(3):241-245. 19. Vendrell JF, Costalat V, Brunel H, Riquelme C, Bonafe A. Stent-assisted coiling of complex middle cerebral artery aneurysms: initial and midterm results. Am J Neuroradiol. 2011;32(2):259-263. 20. Suzuki S, Tateshima S, Jahan R, et al. Endovascular treatment of middle cerebral artery aneurysms with detachable coils: angiographic and clinical outcomes in 115 consecutive patients. Neurosurgery. 2009;64(5):876-888. 21. Bracard S, Abdel-Kerim A, Thuillier L, et al. Endovascular coil occlusion of 152 middle cerebral artery aneurysms: initial and midterm angiographic and clinical results. J Neurosurg. 2010;112(4):703-708. 22. Oishi H, Yoshida K, Shimizu T, Yamamoto M, Horinaka N, Arai H. Endovascular treatment with bare platinum coils for middle cerebral artery aneurysms. Neurol Med Chir (Tokyo). 2009;49(7):287-293. 23. Brinjikji W, Lanzino G, Cloft HJ, Rabinstein A, Kallmes DF. Endovascular treatment of middle cerebral artery aneurysms: a systematic review and singlecenter series. Neurosurgery. 2011;68(2):397-402. 24. Yasargil MG. Microneurosurgery. Vol 1. New York, NY: Thieme Startton; 1984. 25. Suzuki J, Yoshimoto T, Kayama T. Surgical treatment of middle cerebral artery aneurysms. J Neurosurg. 1984;61(1):17-23. 26. Ogilvy CS, Crowell RM, Heros RC. Surgical management of middle cerebral artery aneurysms: experience with transylvian and superior temporal gyrus approaches. Surg Neurol. 1995;43(1):15-22. 27. Rinne J, Hernesniemi J, Niskanen M, Vapalahti M. Analysis of 561 patients with 690 middle cerebral artery aneurysms: anatomic and clinical features as correlated to management outcome. Neurosurgery. 1996;38(1):2-11. 28. Chyatte D, Porterfield R. Nuances of middle cerebral artery aneurysm microsurgery. Neurosurgery. 2001;48(2):339-346. 29. Güresir E, Schuss P, Berkefeld J, Vatter H, Seifert V. Treatment results for complex middle cerebral artery aneurysms. A prospective single-center series. Acta Neurochir (Wien). 2011;153(6):1247-1252. 30. Rodr ıguez-Hernández A, Gabarrós A, Lawton MT. Contralateral clipping of middle cerebral artery aneurysms: rationale, indications, and surgical technique. Neurosurgery. 2012;71(1 suppl operative):116-123. 31. Lagares A, Gómez PA, Alén JF, et al. Aneurysmal subarachnoid hemorrhage: group of study of cerebrovascular pathology of the Spanish society of neurosurgery management guideline [in Spanish]. Neurocirugia (Astur). 2011;22(2):93-115. 32. Campi A, Ramzi N, Molyneux AJ, et al. Retreatment of ruptured cerebral aneurysms in patients randomized by coiling or clipping in the International Subarachnoid Aneurysm Trial (ISAT). Stroke. 2007;38(5):1538-1544. 33. Wolstenholme J, Rivero-Arias O, Gray A, et al. International Subarachnoid Aneurysm Trial (ISAT) Collaborative Group. Treatment pathways, resource use, and costs of endovascular coiling versus surgical clipping after aSAH. Stroke. 2008; 39(1):111-119. 34. Mitchell P, Kerr R, Mendelow AD, Molyneux A. Could late rebleeding overturn the superiority of cranial aneurysm coil embolization over clip ligation seen in the International Subarachnoid Aneurysm Trial? J Neurosurg. 2008;108(3):437-442. 35. Ryttlefors M, Howells T, Nilsson P, Ronne-Engström E, Enblad P. Secondary insults in subarachnoid hemorrhage: occurrence and impact on outcome and clinical deterioration. Neurosurgery. 2007;61(4):704-714. 36. Morgan MK, Mahattanakul W, Davidson A, Reid J. Outcome for middle cerebral artery aneurysm surgery. Neurosurgery. 2010;67(3):755-761. 37. Spetzler RF, Sanai N. The quiet revolution: retractorless surgery for complex vascular and skull base lesions. J Neurosurg. 2012;116(2):291-300. 38. Lawton MT, Quiñones-Hinojosa A. Double reimplantation technique to reconstruct arterial bifurcations with giant aneurysms. Neurosurgery. 2006;58: 347-353. 39. Huang AP, Arora S, Wintermark M, Ko N, Tu YK, Lawton MT. Perfusion computed tomographic imaging and surgical selection with patients after poorgrade aneurysmal subarachnoid hemorrhage. Neurosurgery. 2010;67(4):964-974. MCA ANEURYSMS NEUROSURGERY VOLUME 72 | NUMBER 3 | MARCH 2013 | 427 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. Aneurismas ACM A. Rodríguez-Hernández 70 Aneurismas ACM A. Rodríguez-Hernández 71 2º Artículo Aneurismas ACM A. Rodríguez-Hernández 72 Aneurismas ACM A. Rodríguez-Hernández 73 Flash Fluorescence With Indocyanine Green Videoangiography to Identify the Recipient Artery for Bypass With Distal Middle Cerebral Artery Aneurysms: Operative Technique BACKGROUND: Distal middle cerebral artery (MCA) aneurysms frequently have nonsaccular morphology that necessitates trapping and bypass. Bypasses can be difficult because efferent arteries lie deep in the opercular cleft and may not be easily identifiable. OBJECTIVE: We introduce the “flash fluorescence” technique, which uses videoangiography with indocyanine green (ICG) dye to identify an appropriate recipient artery on the cortical surface for the bypass, enabling a more superficial and easier anastomosis. METHODS: Flash fluorescence requires 3 steps: (1) temporary clip occlusion of the involved afferent artery; (2) videoangiography demonstrating fluorescence in uninvolved arteries on the cortical surface; and (3) removal of the temporary clip with flash fluorescence in the involved efferent arteries on the cortical surface, thereby identifying a recipient. Alternatively, temporary clips can occlude uninvolved arteries, and videoangiography will demonstrate initial fluorescence in efferent arteries during temporary occlusion and flash fluorescence in uninvolved arteries during reperfusion. RESULTS: From a consecutive series of 604 MCA aneurysms treated microsurgically, 22 (3.6%) were distal aneurysms and 11 required a bypass. The flash fluorescence technique was used in 3 patients to select the recipient artery for 2 superficial temporal artery-to-MCA bypasses and 1 MCA-MCA bypass. The correct recipient was selected in all cases. CONCLUSION: The flash fluorescence technique provides quick, reliable localization of an appropriate recipient artery for bypass when revascularization is needed for a distal MCA aneurysm. This technique eliminates the need for extensive dissection of the efferent artery and enables a superficial recipient site that makes the anastomosis safer, faster, and less demanding. KEY WORDS: Distal middle cerebral artery aneurysms, Indocyanine green videoangiography, Intracranial bypass, Recipient artery, Superficial temporal artery-middle cerebral artery bypass Neurosurgery 70[ONS Suppl 2]:ons209–ons220, 2012 DOI: 10.1227/NEU.0b013e31823158f3 Most middle cerebral artery (MCA) aneurysms are located at the bior trifurcation of the MCA in the proximal sylvian fissure, 1 but2%to6%ofMCA aneurysms are located in the distal sylvian fissure, 2-5 typically along insular segments that run between the limen insulae and the circular sulcus. Microsurgical treatment of distal MCA aneurysms is more demanding than proximal MCA aneurysms because the distal sylvian fissure is more difficult to split, there are fewer anatomic landmarks to guide the dissection, and distal aneurysms frequently have nonsaccular morphology that necessitates trapping and bypass. 2,4,6 Bypasses to efferent arteries can be technically difficult because they lie deep within the opercular Ana Rodrl´guez-Herna ´ndez, MD Michael T. Lawton, MD Department of Neurological Surgery, University of California, San Francisco, California Correspondence: Michael T. Lawton, MD, Department of Neurological Surgery, University of California at San Francisco, 505 Parnassus Avenue, M780, San Francisco, CA 94143-0112. E-mail: [email protected] Received, March 15, 2011. Accepted, June 8, 2011. Published Online, August 9, 2011. Copyright ª2011 by the Congress of Neurological Surgeons WHAT IS THIS BOX? A QR Code is a matrix barcode readable by QR scanners,mobile phones with cameras, and smartphones. The QR Code above links to Supplemental Digital Content from this article. ABBREVIATIONS: ICG, indocyanine green; MCA, middle cerebral artery; STA, superficial temporal artery Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www.neurosurgery-online.com). CEREBROVASCULAR Operative Technique NEUROSURGERY VOLUME 70 | OPERATIVE NEUROSURGERY 2 | JUNE 2012 | ons209 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. Aneurismas ACM A. Rodríguez-Hernández 80 The MCA trunks were followed into the insular recess where the aneurysm was encountered. The afferent artery was identified, but the efferent artery was not visualized. The flash fluorescence technique was used to select the cortical recipient artery from 3 angular arteries exiting the distal sylvian fissure (Figure 8). Temporary clips were placed proximally on 3 arteries that were uninvolved with the aneurysm, leaving the afferent artery to the aneurysm open (indirect technique). ICG videoangiography illuminated 2 of the angular arteries on the frontal side of the sylvian fissure. The temporary clips were then removed, with flash fluorescence in the uninvolved arteries on the temporal side of the fissure (see Video 2, Supplemental Digital Content 2, http://links.lww.com/NEU/A427, in which ICG videoangiography demonstrates the flash fluorescence technique for case 3). The STAMCA bypass was completed and the aneurysm clip occluded proximally. Postoperative angiography revealed complete thrombosis of the distalMCAaneurysmandpatencyoftheSTA-MCAbypass(Figure 9). The patient was discharged home on postoperative day 4 and was neurologically intact at the 6-week follow-up evaluation. DISCUSSION Distal MCA aneurysms are rare, accounting for 3.6% of the total number of MCA aneurysms in our surgical experience. Half of these aneurysms required bypass as part of their treatment, FIGURE 7. Case 3, diagnostic studies. A, noncontrast, axial head CT showed a hyperdense lesion in the left insular region. B, CT angiography (sagittal view), and C, catheter angiography (left common carotid injection, anterior oblique view). Both revealed a fusiform aneurysm (arrow) located at the M2-M3 junction that was smaller than the lesion seen on CT scans, consistent with intraluminal thrombus. D, angiography with 3D reconstruction showed this aneurysm to be on a branch from the superior trunk of the left MCA. MCA, middle cerebral artery. RODRl´GUEZ-HERNA ´NDEZ AND LAWTON ons216 | VOLUME 70 | OPERATIVE NEUROSURGERY 2 | JUNE 2012 www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. Aneurismas ACM A. Rodríguez-Hernández 81 FLASH FLUORESCENCE FOR MCA BYPASS NEUROSURGERY VOLUME 70 | OPERATIVE NEUROSURGERY 2 | JUNE 2012 | ons217 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. Aneurismas ACM A. Rodríguez-Hernández 82 because of fusiform or dolichoectatic morphology, giant size, infectious etiology, and/or intraluminal thrombus that prevented direct clipping. Extracranial-intracranial bypass techniques are useful because the superficial temporal artery is so applicable to MCAterritoryrevascularization. 6,11 Intracranial-intracranial bypass techniques that reconstruct efferent arteries using parent or adjacent arteries are also applicable to distal MCA aneurysms, 12,13 . Primary reanastomosis of the afferent and efferent arteries, reimplantation of efferent arteries, and intracranial bypass with radial artery grafts were all used in our experience. 12,14 Acritical FIGURE 9. Case 3, postoperative angiogram. Left common carotid artery angiography (anteroposterior [A] and lateral views [B]) demonstrated no aneurysm filling. Left external carotid artery angiography (anteroposterior [C] and lateral views [D]) demonstrated patency of the STA-MCA bypass (red circle) and retrograde filling back to the site of the thrombosed aneurysm. MCA, middle cerebral artery; STA, superficial temporal artery. FIGURE 8. Case 3, intraoperative pictures. A, wide splitting of the sylvian fissure identified the superior and inferior trunks of MCA. B, the afferent artery was traced to the aneurysm (*), which was white in color and fusiform, located deep in the insular recess. C, 3 potential recipient arteries were observed exiting the distal sylvian fissure. D, temporary clips were placed on 3 arteries that were uninvolved with the aneurysm, leaving the afferent artery open to supply the aneurysm. E, ICG videoangiography illuminated 2 of the angular arteries on the frontal side of the sylvian fissure. F, the temporary clips were then removed and flash fluorescence was observed in the uninvolved arteries on the temporal side of the fissure (indirect technique). G, after performing the STA-MCA bypass, the afferent artery was clip occluded proximally. ST, superior trunk; IT, inferior trunk; MCA, middle cerebral artery; ICG, indocyanine green; STA, superficial temporal artery; ICA, internal carotid artery; CNII, optic nerve. RODRl´GUEZ-HERNA ´NDEZ AND LAWTON ons218 | VOLUME 70 | OPERATIVE NEUROSURGERY 2 | JUNE 2012 www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. Aneurismas ACM A. Rodríguez-Hernández 83 element of the procedure is the appropriate selection of the recipient artery, 15,16 regardless of the bypass technique selected. The obvious way to select the recipient artery is to trace the efferent artery from the aneurysm to an open surgical corridor where the bypass can be performed comfortably. However, efferent arteries from distal MCA aneurysms are difficult to visualizedeepintheinsularrecessorcircularsulcus. 2,6 Large or giant aneurysms can cover or hide this outflow anatomy. Overlying brain consists of pars triangularis, pars opercularis, preand postcentral gyri, and superior temporal gyrus, which harbor eloquent function, particularly in the dominant hemisphere. 1 Splitting the sylvian fissure and separating frontal and temporal lobe is more difficult distally than proximally because the sylvian cistern ends and opercular surfaces are adherent. Opercular arteries help define the subarachnoid dissection plane, but are smaller in caliber than the sphenoidal and insular segments and provide less plane of separation. An overlying confluence of superficial middle cerebral, frontoparietal (Trolard), and posterior temporal (Labbe) veins can also impair access to the distal fissure. 2 Theseanatomicandtechnical limitations often result in a distal sylvian corridor around the efferent artery that is narrow, confining, and not favorable for a bypass. Some neurosurgeons have suggested using navigation and awake craniotomy to overcome some of these limitiations. 17 Others have proposed intraoperative angiography or superselective ICG angiography to select the recipient artery, but these techniques require endovascular access, catheterization of the afferent artery under fluoroscopic guidance, and systemic heparinization. 18 The flash fluorescence technique offers a simple alternative to efferent artery dissection or intraoperative catheter angiography. This technique clearly identifies the efferent artery on the cortical surface, often several centimeters downstream from the artery’s exit from the aneurysm. Identification of the recipient on the cortical surface makes additional dissection deep in the distal sylvian fissure unnecessary and spares patients the associated morbidity. The anastomosis is significantly easier to perform on the cortical surface than in a narrow sylvian corridor. Brain retraction is not necessary, and the overall procedure is quicker. The more distal location of the anastomosis requires extending the craniotomy further posteriorly than the standard pterional craniotomy; failure to extend the craniotomy may position the recipient artery beyond the exposed brain surface. The bypass provides flow in the recipient artery that is both antegrade and retrograde, back to its junction with the trapped aneurysm. The flash fluorescence technique is useful with all types of bypasses, including the STA-MCA and radial artery interposition bypasses shown here. The technique is also applicable with other in situ bypasses, and we recently used it for an M3-to-M3 side-to-side bypass in a patient with a diminutive STA. The flash fluorescence technique minimizes the dissection on the distal side of the aneurysm. In cases 1 and 3, proximal occlusion was sufficient because the aneurysms were unruptured and thick-walled. Proximal occlusion and distal bypass induced complete aneurysm thrombosis in both cases. However, it was still necessary in case 2 to identify the efferent trunk to complete the aneurysm trapping for suction decompression. The flash fluorescence technique minimized, but did not eliminate, the need for distal aneurysm dissection in this case. CONCLUSION The flash fluorescence technique provides quick and reliable intraoperative localization of the appropriate recipient artery for bypass when revascularization is needed for a distal MCA aneurysm. This technique eliminates the need for extensive deep dissection of efferent arteries and enables a more superficial recipient site that makes the anastomosis safer, faster, and less technically demanding. Disclosure The authors have no personal financial or institutional interest in any of the drugs, materials, or devices described in this article. REFERENCES 1. Gibo H, Carver C, Rhoton AL Jr, et al. Microsurgical anatomy of the middle cerebral artery. J Neurosurg. 1981;54(2):151-169. 2. Joo SP, Kim TS, Choi JW, et al. Characteristics and management of ruptured distal middle cerebral artery aneurysms. Acta Neurochir (Wien). 2007;149(7): 661-667. 3. Rinne J, Hernesniemi J, Niskanen M, Vapalahti M. Analysis of 561 patients with 690 middle cerebral artery aneurysms: anatomic and clinical features as correlated to management outcome. Neurosurgery. 1996;38(1):2-11. 4. Lee SH, Bang JS. Distal middle cerebral artery M4 aneurysm surgery using navigation-CT angiography. J Korean Neurosurg Soc. 2007;42(6):478-480. 5. Horiuchi T, Tanaka Y, Takasawa H, Murata T, Yako T, Hongo K. Ruptured distal middle cerebral artery aneurysm. J Neurosurg. 2004;100(3):384-388. 6. Dashti R, Hernesniemi J, Niemelä M, et al. Microneurosurgical management of distal middle cerebral artery aneurysms. Surg Neurol. 2007;67(6):553-563. 7. Raabe A, Nakaji P, Beck J, et al. Prospective evaluation of surgical microscopeintegrated intraoperative near-infrared indocyanine green videoangiography during aneurysm surgery. J Neurosurg. 2005;103(6):982-989. 8. Woitzik J, Horn P, Vajkoczy P, Schmiedek P. Intraoperative control of extracranial-intracranial bypass patency by near-infrared indocyanine green videoangiography. J Neurosurg. 2005;102(4):692-698. 9. Holm C, Mayr M, Höfter E, Dornseifer U, Ninkovic M. Assessment of the patency of microvascular anastomoses using microscope-integrated near-infrared angiography: a preliminary study. Microsurgery. 2009;29(7):509-514. 10. Schuette AJ, Cawley CM, Barrow DL. Indocyanine green videoangiography in the management of dural arteriovenous fistulae. Neurosurgery. 2010;67(3): 658-662. 11. Sekhar LN, Stimac D, Bakir A, Rak R. Reconstruction options for complex middle cerebral artery aneurysms. Neurosurgery. 2005;56(1 suppl):66-74; discussion 66-74. 12. Sanai N, Zador Z, Lawton M. Bypass surgery for complex brain aneurysms: an assessment of intracranial-intracranial bypass. Neurosurgery. 2009;65(4): 670-683. 13. Seo BR, Kim TS, Joo SP, et al. Surgical strategies using cerebral revascularization in complex middle cerebral artery aneurysms. Clin Neurol Neurosurg. 2009;111(8): 670-675. 14. Quiñones-Hinojosa A, Lawton MT. In situ bypass in the management of complex intracranial aneurysms: technique application in 13 patients. Neurosurgery. 2008; 62(6 suppl 3):1442-1449. 15. Mohit AA, Sekhar LN, Natarajan SK, Britz GW, Ghodke B. High-flow bypass grafts in the management of complex intracranial aneurysms. Neurosurgery. 2007; 60(2 suppl 1):105-123. FLASH FLUORESCENCE FOR MCA BYPASS NEUROSURGERY VOLUME 70 | OPERATIVE NEUROSURGERY 2 | JUNE 2012 | ons219 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. Aneurismas ACM A. Rodríguez-Hernández 84 16. Kadri P, Krisht A, Gandhi G. An anatomic mathematical measurement to find an adequate recipient M4 branch for superficial temporal artery to middle cerebral artery bypass surgery. Neurosurgery. 2007;61(3):74-78. 17. Lüders JC, Steinmetz MP, Mayberg MR. Awake craniotomy for microsurgical obliteration of mycotic aneurysms: technical report of three cases. Neurosurgery. 2005;56(1 suppl):E201. 18. Gruber A, Dorfer C, Bavinzski G, Standhardt H, Ferraz-Leite H, Knosp E. Superselective indocyanine green angiography for selective revascularization in the management of peripheral cerebral aneurysms [published online ahead of print March 17, 2011]. AJNR Am J Neuroradiol. doi: 10.3174/ajnr.A2424. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www.neurosurgery-online.com). COMMENTS This article describes distal MCA-bypass surgery supported by ICG angiography in a very selected population of aneurysm patients. Very few publications have reported similar work. The described innovation in surgical technique is of significant interest to vascular neurosurgeons. The conclusion of the authors, that this technique "makes the anastomosis safer, faster and less technically demanding" is very true. The article is relatively short and clear in design. The case description is concise. The surgical technique is well illustrated via radiological scans, images of the intraoperative site, and short videos. This publication represents a valuable addition to the current literature on this topic. Jacek Szczygielski Joachim Oertel Mainz, Germany This article describes a very useful and innovative technique for bypass surgery in patients harboring distal MCA aneurysms. The procedure is well illustrated and represents an important adjunctive technique in the management of cerebral aneurysms by therapeutic parent artery occlusion under bypass protection. Aneurysm dissection in the depth of the sylvian fissure can be challenging and can be the source of procedural morbidity in some cases. To overcome the problem of extensive dissection, a superficial cortical branch can be chosen for bypass surgery instead. The authors present a simple and effective technique to identify the correct cortical recipient artery. We have recently described a similar technique, ie, superselective intraoperative ICG angiography, as a possible solution for the same problem. 1 In compared with our technique, the procedure reported by the authors has the clear advantage that neither intraoperative microcatheter manipulation nor intraarterial ICG dye injection is required. Christian Dorfer Andreas Gruber Vienna, Austria 1. Gruber A, Dorfer C, Bavinzski G, Standhardt H, Ferraz-Leite H, Knosp E. Superselective indocyanine green angiography for selective revascularization in the management of peripheral cerebral aneurysms [published online ahead of print November 16, 2011]. AJNR Am J Neuroradiol doi: 10.3174/ajnr. A2424. The very experienced group at USF nicely introduces the "flash fluorescence" technique using ICG dye to identify an appropriate recipient cortical artery for a bypass and thereby making it safer, easier, and faster. In Helsinki, we have actively been using ICG angiography since its introduction and have found it very useful in aneurysm surgery. 1 As the authors state, distal MCA aneurysms are often challenging, not only because of the often needed bypass due to their fusiform nature, but also, when clippable and small in size, their dissection sometimes necessitates the use of neuronavigation. So far, these aneurysms are better treated by microsurgery, 2 and the current article addresses the importance of dedicated neurovascular centers being able to do that. As can be seen, there is constant ongoing development also in and around microsurgical techniques ultimately benefiting the patients. Mika Niemelä Juha Hernesniemi Helsinki, Finland 1. Dashti R, Laakso A, Niemelä M, Porras M, Hernesniemi JA. Microscope-integrated near-infrared green video angiography during surgery of intracranial aneurysms: the Helsinki experience. Surg Neurol 2009;71(5):543-550. 2. Dashti R, Hernesniemi J, Niemelä M, et al. Microneurosurgical management of distal middle cerebral artery aneurysms. Surg Neurol 2007;67:553-563. RODRl´GUEZ-HERNA ´NDEZ AND LAWTON ons220 | VOLUME 70 | OPERATIVE NEUROSURGERY 2 | JUNE 2012 www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. Aneurismas ACM A. Rodríguez-Hernández 85 3er Artículo Aneurismas ACM A. Rodríguez-Hernández 86 Aneurismas ACM A. Rodríguez-Hernández 87 Contralateral Clipping of Middle Cerebral Artery Aneurysms: Rationale, Indications, and Surgical Technique BACKGROUND: Contralateral clipping of middle cerebral artery (MCA) aneurysms seems dangerous and ill advised but could become an important technique because of the prevalence of MCA aneurysms, the limitations of endovascular therapy, and increasing interest in less invasive techniques. OBJECTIVE: To define patient selection, surgical technique, and results with contralateral MCA aneurysm clipping. METHODS: Forty-two patients with bilateral MCA aneurysms were treated either in 1 stage with a single craniotomy and contralateral aneurysm clipping (group 1, 11 patients) or in 2 stages with bilateral craniotomy (group 2, 31 patients). Surgical technique consisted of ipsilateral sylvian fissure split, subfrontal dissection, contralateral sylvian fissure split, mobilization of medial orbital gyrus, and contralateral aneurysm clipping. RESULTS: Group 1 patients were older than group 2 patients (60.3 vs 55.4 years, respectively). Clinical presentation with subarachnoid hemorrhage was less common in group 1. Nine group 1 patients (82%) had left-sided craniotomies, and the ipsilateral aneurysm was larger than the contralateral aneurysm. All aneurysms were clipped without intraoperative complications (136 aneurysms). Mean neurosurgical charges were decreased by contralateral MCA aneurysm clipping: $39 297 in group 1 vs $57 977 in group 2. CONCLUSION: Contralateral MCA aneurysm clipping can be viewed as an extreme microsurgical technique or as a less invasive technique that spares patients a second craniotomy in the management of bilateral aneurysms. This technique is acceptable in selected patients with contralateral aneurysms that are unruptured, have simple necks, project inferiorly or anteriorly, are associated with short M1 segments, and reside in older patients with sylvian fissures widened by brain atrophy. KEY WORDS: Bilateral aneurysms, Contralateral clipping, Middle cerebral artery aneurysm, Minimally invasive surgery, Mirror aneurysms Neurosurgery 71[ONS Suppl 1]:ons116–ons124, 2012 DOI: 10.1227/NEU.0b013e31824d8f66 Contralateral aneurysm clipping has been well described and practiced for ophthalmic artery, superior hypophyseal artery, and internal carotid artery (ICA) bifurcation aneurysms. 1-6 An approach to the aneurysm from the opposite side might provide a better view or a medial perspective that can improve surgical treatment. For example, a medially projecting ophthalmic artery aneurysm typically requires anterior clinoidectomy and dissection of the distal dural ring with an ipsilateral approach but may not require either with a contralateral approach. Eliminating clinoidectomy and paraclinoid dissection reduces the risk of optic nerve morbidity and visual deficits. Similarly, a contralateral ICA bifurcation aneurysm associated with other ipsilateral aneurysms can be exposed with minimal additional subfrontal dissection, sparing the patient a second craniotomy. The typical superior projection of most ICA bifurcation aneurysms affords adequate views of the Ana Rodríguez-Herna ´ndez, MD* Andreu Gabarro ´s, MD‡ Michael T. Lawton, MD* *Department of Neurological Surgery, University of California, San Francisco, California; ‡Department of Neurological Surgery, Hospital de Bellvitge, Barcelona, Spain Correspondence: Michael T. Lawton, MD, Department of Neurological Surgery, University of California at San Francisco, 505 Parnassus Ave, M780, San Francisco, CA 94143-0112. E-mail: [email protected] Received, September 26, 2011. Accepted, January 4, 2012. Published Online, February 2, 2012. Copyright ª2012 by the Congress of Neurological Surgeons ABBREVIATIONS: ACA, anterior cerebral artery; ICA, internal carotid artery; MCA, middle cerebral artery; mRS, modified Rankin Scale CEREBROVASCULAR Technique Assessment ons116 | VOLUME 71 | OPERATIVE NEUROSURGERY 1 | SEPTEMBER 2012 www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. Aneurismas ACM A. Rodríguez-Hernández 88 neck and posterior perforators for safe clipping. Contralateral aneurysm clipping works well for other aneurysms located at short distances across the midline. Contralateral paramedian aneurysms include A1 segment anterior cerebral artery (ACA), A1-A2 junction, P1 segment posterior cerebral artery, and superior cerebellar artery aneurysms. These aneurysms around or near the circle of Willis are favorable for contralateral clipping, but aneurysms outside or beyond the circle of Willis are less favorable. Contralateral clipping of middle cerebral artery (MCA) aneurysms has been described 7-10 but is not practiced widely because of long dissection distances, limited view, and impaired maneuverability FIGURE 1. Microsurgical technique for contralateral middle cerebral artery (MCA) aneurysm clipping. A, left pterional craniotomy and (B) transsylvian dissection expose the ipsilateral MCA aneurysm for clipping. Dissection to the contralateral MCA aneurysm follows a lateral subfrontal trajectory that requires minimal retraction, often just with gentle pressure from an instrument. C, the ipsilateral frontal lobe is freed from the optic tract and chiasm. The contralateral frontal lobe and olfactory tract are dissected from the contralateral optic nerve along its course from the optic canal to the chiasm. D, subfrontal exposure accesses the contralateral carotid and sylvian cisterns, which are opened widely. E, the contralateral sylvian fissure is split from its medial side, following the M1 MCA segment to the aneurysm. F, retraction on the contralateral medial orbital gyrus may be needed to expose the distal sylvian fissure and can be done with the suction rather than a fixed retractor blade. G, the aneurysm is clipped with a straight clip. CONTRALATERAL CLIPPING OF MCA ANEURYSMS NEUROSURGERY VOLUME 71 | OPERATIVE NEUROSURGERY 1 | SEPTEMBER 2012 | ons117 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. Aneurismas ACM A. Rodríguez-Hernández 89 in the operative corridor. Furthermore, complications like intraoperative aneurysm rupture are difficult to manage with this approach. Contralateral clipping of MCA aneurysms seems dangerous and ill advised, and some neurosurgeons have condemned or abandoned this technique. However, others have adopted this technique because of the prevalence of MCA aneurysms, the limitations of endovascular therapy with these particular lesions, and increasing patient interest in less invasive aneurysm management. The controversy surrounding this technique demands further analysis and consensus. Our confidence in contralateral clipping of MCA aneurysms has grown, but we contend that adoption of this technique depends on patient selection and surgical technique, which are defined in this report. PATIENTS AND METHODS Clinical Material This study was approved by the Institutional Review Board and conducted in compliance with Health Insurance Portability and Accountability Act regulations. The prospectively collected database of the Vascular Neurosurgery Service at the University of California, San Francisco, was searched to identify all patients with MCA aneurysms. Between August 1997 and December 2010, 566 patients harboring 606 MCA aneurysms were treated microsurgically by the senior author (M.T.L.). Forty-two of these patients (7.4%) had bilateral MCA aneurysms that were treated: 11 patients in 1 stage with a single craniotomy and contralateral MCA aneurysm clipping (group 1) and 31 patients in 2 stages with bilateral craniotomy (group 2). Medical records, radiographic studies, intraoperative photographs, and clinical follow-up evaluations were retrospectively reviewed. Clinical outcomes were assessed by a nurse clinician under the supervision of a neurologist using the modified Rankin Scale (mRS) 6 weeks after surgery and at last follow-up. The outcome was considered improved when the difference between the preoperative mRS and the postoperative mRS was positive, unchanged when there was no difference, and worse when that difference was negative. Treatment costs were estimated by neurosurgical hospital charges. Surgical Technique for Contralateral Clipping of MCA Aneurysms A standard pterional craniotomy is used for contralateral MCA aneurysm clipping (Figure 1A). The side of the craniotomy is selected ipsilateral to the larger or more complex of the 2 MCA aneurysms, placing the smaller or simpler aneurysm on the contralateral side (Figure 1B). The patient is positioned supine with the head fixed in a Mayfield frame and rotated 15to 20away from the side of the ipsilateral MCA aneurysm, with slight extension. Mannitol is administered at the start of the operation for brain relaxation. Ventricular or lumbar drains are not used; cerebrospinal fluid is drained by widely opening the subarachnoid cisterns and fenestrating the lamina terminalis. The incision starts at the zygomatic arch 1 cm anterior to the tragus and follows the hairline to the midline. The temporalis muscle is mobilized anteroinferiorly, and frontotemporal craniotomy is made with a single temporal burr hole. The pterion and the medial part of the sphenoid wing are drilled down to the lateral edge of the superior orbital fissure, flattening the bone connecting the anterior and middle cranial fossae. After opening of the dura, the ipsilateral sylvian fissure is opened widely under the microscope. The M1 MCA is exposed for proximal control, and the aneurysm is dissected and clipped. Ipsilateral clips can interfere with the contralateral approach, in which case ipsilateral clipping is deferred until after contralateral clipping. The contralateral approach begins at the ipsilateral ICA bifurcation, where the A1 ACA is identified and followed to the anterior communicating artery complex (Figure 1C). Fenestration of the lamina terminalis releases cerebrospinal fluid to slacken the brain for subsequent frontal retraction. The chiasmatic and lamina terminalis cisterns are opened extensively, and arachnoidal trabeculations between the inferior frontal lobe and optic nerve are incised. The optic nerve and olfactory tract are separated for further frontal lobe elevation. This arachnoidal dissection extends anteriorly to the optic canal to free the frontal lobe and to open the subfrontal corridor (Figure 1D). Mobilization of the frontal lobe, either with a fixed retractor on the medial orbital gyrus or with dynamic retraction from a surgical instrument, exposes the contralateral A1 ACA. This segment is traced to the ICA bifurcation, which rises above the plane of the optic apparatus. The carotid cistern is opened widely to visualize the origin of M1 MCA and arachnoid of the sylvian cistern (Figure 1E). FIGURE 2. A, preoperative magnetic resonance angiogram (anteroposterior view) demonstrated bilateral middle cerebral artery (MCA) aneurysms. The inferior projection of the right aneurysm made it ideal for contralateral clipping. B, through a left pterional craniotomy and subfrontal approach to the contralateral side, the right-sided aneurysm was exposed in the sylvian fissure. Note the sylvian veins bridging from the frontal lobe to the sphenoparietal sinus. C, the superior and inferior trunks coursed superiorly away from the neck, and the aneurysm was clipped with a simple curved clip. D, postoperative digital subtraction angiography (right internal carotid artery injection, anteroposterior view) demonstrated complete occlusion of the aneurysm. RODRÍGUEZ-HERNA ´NDEZ ET AL ons118 | VOLUME 71 | OPERATIVE NEUROSURGERY 1 | SEPTEMBER 2012 www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. Aneurismas ACM A. Rodríguez-Hernández 96 Aneurismas ACM A. Rodríguez-Hernández 97 4º Artículo Aneurismas ACM A. Rodríguez-Hernández 98 End-to-End Reanastomosis Technique for Fusiform Aneurysms: 3-Dimensional Operative Video Ana Rodríguez-Hernández, MD, Michael T. Lawton, MD Department of Neurological Surgery, University of California at San Francisco, San Francisco, California Intracranial aneurysms with a fusiform morphology are rarely amenable to direct clipping and instead require occlusion techniques that involve revascularization. One such technique is aneurysm trapping and excision with end-to-end reanastomosis of the inflow and outflow arteries. Middle cerebral artery and posterior inferior cerebellar artery (PICA) aneurysms often have redundant parent artery that allows primary reanastomosis. End-to-end anastomosis requires fewer bites than end-to-side anastomosis, and rotation of arteries helps to visualize both suture lines. In this video, we illustrate this technique with 2 different aneurysms. In the first case, a 73-year-old man presented with expressive aphasia and a partially thrombosed, giant serpentine left middle cerebral artery aneurysm. The aneurysm was exposed through a pterional craniotomy; inflow and outflow arteries were temporary clipped; thrombectomy decompressed the aneurysm mass to bring the transected ends together; and end-to-end anastomosis was performed with running suture. Postoperative angiography confirmed filling of the middle cerebral artery territory through a patent anastomosis. In the second case, a 45year-old woman with severe headache had a 7-mm distal p3 PICA aneurysm. A far lateral approach exposed the caudal loop of PICA harboring the aneurysm, and atherosclerosis plus fusiform morphology prevented clipping. The aneurysm was trapped and excised, and the parent artery was reanastomosed. Postoperative angiography confirmed filling of the distal PICA territory through the bypass. End-to-end reanastomosis of the parent artery after aneurysm excision is an efficient revascularization technique for fusiform aneurysms that have 1 afferent and 1 efferent artery, obviating the need for harvesting extracranial donor arteries. Disclosure Dr Lawton receives a royalty from Mizuho America for surgical instruments designed for bypass. Dr Rodríguez-Hernández is supported by a grant from the La Caixa Foundation. The authors have no personal financial or institutional interest in any of the drugs, materials, or devices described in this article. Acknowledgments We thank Guido Hattendorf from Zeiss and Ernesto Ramirez, Magnus Classon, and William Scott from the University of California at San Francisco operating rooms for their technical support. The 3-D video can be viewed at http:// bit.ly/13SXx8S or to view the video on a mobile device, scan this QR Code to link to an anaglyph (red/green) version of this 3-D video. COMMENTS The authors masterfully illustrated the use of end-to-end anastomosis as part of their microsurgical armamentarium for complex brain aneurysm treatment. End-to-end anastomosis without or with graft interposition is a very useful technique for microsurgical vascular reconstruction. Although the indications for bypass during aneurysm surgery are likely diminishing because of advances in endovascular technology, it surely remains a very important tool. It is our responsibility to keep up our bypass skills, especially in times of lower use. I congratulate the authors for sharing their expertise and educating current and future generations on microanastomic techniques and their use. Ricardo A. Hanel Jacksonville, Florida The authors display a nice 3-dimensional technical video of an end-toend anastomosis for fusiform middle cerebral artery and posterior inferior cerebellar artery aneurysms. The technique and pertinent imaging are nicely demonstrated. Although current technologies have made endovascular treatment of most aneurysms possible, certain aneurysms are best managed with open microsurgery. There may be temptation to push the boundaries of endovascular techniques in each of these cases. However, we must not forget that there are instances in which open surgery is the more appropriate and less risky option. This technical video Watch now at http://bit.ly/13SXx8S 3-D Video OPERATIVE NEUROSURGERY VOLUME 10 | NUMBER 1 | MARCH 2014 | 157 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. Aneurismas ACM A. Rodríguez-Hernández 99 demonstrates how a simple, yet elegant, open microsurgical approach safely and effectively cures 2 fusiform aneurysms of intracranial arteries. In addition, the video highlights the importance that patients with intracranial aneurysms be treated at high-volume centers with surgeons skilled in both open and endovascular techniques who can offer an unbiased appraisal of the best treatment for each patient. Mandy J. Binning Erol Veznedaroglu Hamilton, New Jersey The authors nicely demonstrate the utility of an often-overlooked technique for excluding a difficult aneurysm that is not amenable to clip ligation. In the first case, a giant thrombosed middle cerebral aneurysm is excluded, with enough redundancy of the M1 branch to perform a direct end-to-end anastomosis. It was necessary in this case to reduce the mass of the aneurysm to enable enough length to perform the end-to-end anastomosis. This obviously adds some time to the cross-clamp time on the distal middle cerebral territory, and another option would be to consider revascularization of a more distal middle cerebral artery branch with bypass before trapping of the aneurysm. With the present technique, it may be also prudent to have a backup bypass donor vessel (eg, superficial temporal artery) if the end-to-end anastomosis cannot be performed. The second case demonstrates a distal posterior inferior cerebellar artery aneurysm, which is a perfect indication for such a technique if the anatomy and wall of the aneurysm are such that clipping will be impractical or may be associated with a risk of vessel occlusion. I commend the authors on a beautiful surgical result in both of these cases; it provides native anterograde arterial supply without the need for bypass. This technique can also be used with the internal carotid artery directly by using the redundancy of the anterior loop and performing an end-to-end anastomosis after resection of a cavernous sinus tumor (article in press). William T. Couldwell Salt Lake City, Utah RODRÍGUEZ-HERNA ´NDEZ, AND LAWTON, 158 | VOLUME 10 | NUMBER 1 | MARCH 2014 www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. Aneurismas ACM A. Rodríguez-Hernández 100 Aneurismas ACM A. Rodríguez-Hernández 101 VI.- Discusión Aneurismas ACM A. Rodríguez-Hernández 102 Aneurismas ACM A. Rodríguez-Hernández 103 VI.- DISCUSIÓN El tratamiento quirúrgico de los aneurismas de ACM ha demostrado de forma consistente y continúa excelentes resultados clínicos y radiológicos (1, 2, 33, 34, 40, 47, 66, 67, 71, 81, 97, 105, 120, 121, 149, 153). Como se puede observar en la tabla 5 del artículo 1, las series quirúrgicas publicadas en las últimas décadas describen tasas de oclusión completa del aneurisma por encima del 90 % (2, 26, 33, 49, 97, 105, 153, 164, 175, 176). En cuanto a los resultados clínicos, desde un 88% hasta un 100% de los pacientes con aneurismas no rotos tienen un buen resultado neurológico. Para los aneurismas rotos, los resultados neurológicos son algo más variables. La experiencia con 631 aneurismas de ACM en 543 pacientes revisada en este trabajo, demuestra que la microcirugía sigue dando excelentes resultados con un amplio espectro de lesiones y pacientes que incluyen aneurismas gigantes y trombóticos, aneurismas rotos en pacientes con mal grado clínico, y aneurismas no rotos en pacientes de edad avanzada. Con la microcirugía como tratamiento de primera elección, los aneurismas de ACM fueron el aneurisma quirúrgico más común (25 % del total de aneurismas quirúrgicos) y las técnicas quirúrgicas disponibles (clipaje simple, trombectomía, reconstrucción, abordaje contralateral, bypass asistido con flash fluorescence, etc) solucionan con éxito la variedad de anatomías aneurismáticas sin necesidad de tratamiento endovascular. El análisis por subgrupos sugiere que los malos resultados se deben sobre todo a esta política quirúrgica “inclusiva” consistente en manejar de forma agresiva a pacientes Hunt-Hess grado IV y V con hemicraniectomía y evacuación del hematoma, y los aneurismas complejos con trombectomía y bypass. Los resultados de este trabajo apoyan una política consistente en seguir ofreciendo el clipaje como primera opción para los aneurismas de ACM. 1.- Argumentos a Favor de la Cirugía Los aneurismas de la ACM se exponen correctamente con una craneotomía pterional básica. Las craneotomías más agresivas (orbitocigomáticas y orbito-pterional) se utilizan en Aneurismas ACM A. Rodríguez-Hernández 104 casos seleccionados y representaron solo el 10 % de todas las craneotomías. La ubicación lateral y superficial de los aneurismas de ACM permite la miniaturización de la craneotomía pterional, opción cada vez más utilizada en los últimos años del período que ocupa el presente estudio. La craneotomía “mini – pterional” es particularmente útil en los pacientes de más edad porque a menor tamaño de la craneotomía, menor riesgo de desgarros durales y complicaciones secundarias. Además, la habitual atrofia de la cisura Silviana en pacientes mayores permite una fácil exposición del aneurisma obviando la necesidad de una craneotomía más grande. La disección de la cisura de Silvio y la separación de los lóbulos frontal y temporal es una técnica neuroquirúrgica básica que consigue exponer fácilmente y a plena vista, la anatomía relevante para tratar un aneurisma de ACM. Los riesgos asociados con la disección silviana incluyen el sacrificio de alguna vena con el consiguiente infarto venoso, oclusión de alguna rama arterial, transgresión pial y contusiones. Aunque el presente estudio no mide específicamente estos riesgos, la percepción es que fueron mínimos. Habitualmente las venas se pueden movilizar hacia el lóbulo temporal, las ramas arteriales se separan hacia el lóbulo correspondiente y se disecan hasta llegar a los troncos arteriales, la pía se protege para evitar lesiones y los retractores no suelen ser necesarios en esta localización. Cuando los lóbulos frontal y temporal se separan, el campo quirúrgico resultante es amplio y poco profundo, lo que permite una fácil maniobrabilidad para la reparación del aneurisma. Los diferentes tipos de clip (rectos, curvos, fenestrados, en bayoneta, etc.) y las distintas configuraciones de clipaje (simple, con clips apilados, solapados, en intersección, en tándem, etc.) permiten reparar la mayoría de los aneurismas de ACM (89% en nuestra experiencia). Una amplia disección silviana también facilita técnicas más difíciles como la trombectomía/reconstrucción y el bypass/oclusión (ver vídeo artículo 4). Aneurismas ACM A. Rodríguez-Hernández 105 Una importante ventaja de la cirugía es la capacidad para dilucidar la compleja anatomía del cuello del aneurisma, sus ramos superior, inferior e incluso a veces medios y la disposición de las lenticulostriadas circundantes. La percepción obtenida a través de la disección in situ de esta anatomía es habitualmente más informativa que las propias imágenes angiográficas. La manipulación del saco aneurismático durante la disección resultó en un riesgo de rotura intraoperatoria que es mayor que la asociada con la terapia endovascular (5,7 % vs. 3,1 %). Sin embargo, las roturas intraoperatorias de los aneurismas de ACM son mucho más fáciles de manejar que las de otras localizaciones ya que el control proximal requiere un solo clip, el control distal es fácilmente accesible y el campo microquirúrgico es amplio. En la serie presentada, ninguna de las roturas intraoperatorias resultó en una morbilidad o mortalidad añadida. Otra gran ventaja de la cirugía es la flexibilidad para utilizar técnicas no convencionales cuando sea necesario, ya sea de forma pre planificada basada en la anatomía del aneurisma específico o en respuesta a hallazgos intraoperatorios inesperados. La cisura de Silvio es también una puerta de entrada a otros aneurismas de todo el polígono de Willis , permitiendo el clipaje de otros 284 aneurismas en 192 pacientes, incluyendo el clipaje contralateral de aneurismas de ACM en espejo, lo cual ahorró una segunda craneotomía a un total de 30 pacientes. La reparación de un aneurisma de forma eficaz y duradera que ofrece el cierre mecánico del cuello, representa la ventaja más importante que ofrece el clipaje quirúrgico. De hecho, los resultados quirúrgicos fueron excelentes con una oclusión completa del aneurisma en el 98.3% de los casos y sólo una rotura post-tratamiento (0.2 %). Se puede argumentar también que la cirugía ofrece importantes ventajas para el paciente en mal grado clínico que presenta una presión intracraneal elevada: la evacuación de posibles hematomas, una hemicraniectomía descompresiva, y la liberación de LCR al fenestrar la lamina terminalis y la Aneurismas ACM A. Rodríguez-Hernández 112 Aneurismas ACM A. Rodríguez-Hernández 113 VII.- Conclusiones Aneurismas ACM A. Rodríguez-Hernández 114 Aneurismas ACM A. Rodríguez-Hernández 115 VII.- CONCLUSIONES  La cirugía debe seguir siendo el tratamiento de elección para los aneurismas de la ACM, salvo imponderables. La morbilidad quirúrgica es baja y los resultados de los pacientes están principalmente determinados por la presentación neurológica inicial. Un mal grado en la escala HuntHess es a menudo una indicación de tratamiento endovascular, pero se debe considerar que los pacientes con aneurismas de la ACM a menudo se benefician de hemicraniectomía y evacuación del coágulo.  La cirugía abierta consigue tratar la mayoría de aneurismas de ACM mediante técnicas de clipaje convencional, pero además amplía las posibilidades a otras técnicas no convencionales como la trombectomía /reconstrucción y el bypass/oclusión.  La técnica de flash de fluorescencia proporciona la localización intraoperatoria rápida y fiable de la arteria receptora apropiada para el bypass cuando se necesita revascularización para un aneurisma de ACM distal. Esta técnica elimina la necesidad de una amplia disección profunda de las arterias eferentes y permite a un sitio receptor más superficial que hace la anastomosis más segura, más rápida y menos exigente desde el punto de vista técnico.  El clipaje contralateral de aneurismas de ACM puede ser visto como una técnica menos invasiva en el tratamiento de aneurismas bilaterales que ahorra al paciente una segunda craneotomía. Este trabajo demuestra que la técnica es factible y segura. Esta técnica está indicada en pacientes con aneurismas de ACM contralaterales no rotos, con cuello simple, que proyecten inferior o anteriormente, que se asocian con segmentos M1 cortos y en pacientes de edad avanzada con cisuras de Silvio amplia debido a la atrofia cerebral asociada a la edad. Aneurismas ACM A. Rodríguez-Hernández 116  Los resultados quirúrgicos de esta revisión pueden servir como el referente al que deben aspirar los resultados endovasculares antes de considerar la terapia endovascular como alternativa para estas lesiones. Aneurismas ACM A. Rodríguez-Hernández 117 VIII.- Bibliografía Aneurismas ACM A. Rodríguez-Hernández 118 Aneurismas ACM A. Rodríguez-Hernández 119 VIII.- BIBLIOGRAFIA 1. Abla AA, Jahshan S, Kan P, Mokin M, Dumont TM, Eller JL, et al.: Results of endovascular treatment of middle cerebral artery aneurysms after first giving consideration to clipping. Acta Neurochir (Wien) 155:559–568, 2013 2. Abla AA, Lawton MT: Predictors of Complications with unruptured MCA aneurysm Clipping in a Surgically Treated series of 416 patients. A Clip First approach is still best. World Neurosurg:2015 3. Acosta-Rua GJ, Lyerly JG, Sullivan EJ, Lyerly JG, Chandler HC: Cerebral aneurysm. J Fla Med Assoc 63:847–849, 1976 4. 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