Cognitive performance in chronic migraine

131 https://doi.org/10.1590/0004-282X20200024 EDITORIAL Cognitive performance in chronic migraine Desempenho cognitivo na enxaqueca crônica Isabel Pavão MARTINS1,2,3 1Universidade de Lisboa, Faculty of Medicine, Lisbon, Portugal. 2Universidade de Lisboa, Institute of Molecular Medicine, Lisbon, Portugal. 3Hospital Universitário de Santa Maria, Head of Headache Outpatient Clinic, Consultant Neurologist, Lisbon, Portugal. Isabel Pavão MARTINS https:// orcid.org/0000-0002-9611-7400 Correspondence: Isabel Pavão Martins; E-mail: ipavaomartins@ gmail.com Conflict of interest: There is no conflict of interest to declare. Received on February 20, 2020 Accepted on February 28, 2020 Migraine is a ubiquitous disorder that affects 15% of the world population, particularly women during their most productive years1. Migraine produces a variety of symptoms, but its most common presentation consists of recurrent attacks of disabling headaches associated to nausea and intolerance to all sensory stimuli. During attacks, patients often experience cognitive difficulties, with poor ability to concentrate or think clearly, and are unable to deal with multiple tasks2,3. Thecause of this transient cognitive dysfunction is not known but has been attributed to the complex and widespread brain dysfunction underlying the development of the attacks4,5,6, because it cannot be simply explained by pain. In fact, it is not observed in other primary headaches, and the cognitive difficulties are often present during the premonitory and resolution phases of migraine, i.e., both before the onset and after the resolution of pain7,8. The finding of repetitive, transient cognitive dysfunction during migraine attacks raises questions regarding its long-term effects in learning and cognitive development in children with migraine or in later life of adults, especially because migraine has also been related to silent brain lesions, regional atrophy and disorders of brain connectivity9,10. Roughly 2% of the population and 8% of subjects with migraine have a severe form of the disorder, called chronic migraine, which is characterized by very frequent attacks that almost merge into each other, often leading to a background of pain with super imposed aggravations11,12. Although it is recognized that migraine-related cognitive dysfunction depends on attack frequency13,14, it is not known if it reverts between attacks in cases of chronic migraine, with patients experiencing 15 or more days per month with headache, according to the current definition. Moreover,patients with chronic migraine often have medication overuse and many co-morbidities, such as depression, sleep disorders, anxiety and their respective treatment, which may impactcognition. The article by Latysheva NV etal., published in Arquivos de Neuro-Psiquiatria15, adds a relevant piece of information to this topic. The authors performed a neuropsychological evaluation in 144 individuals with chronic migraine (outside acute exacerbations) and compared them to controls with episodic migraine, matched for age, gender and literacy. Individuals with severe depression were excluded, and cognitive performance was controlled for the severity of depressive symptoms and medication overuse. The authors found that subjects with chronic migraine scored below controls in all applied cognitive tests, including attention and processing speed (Digit Symbol Substitution Test), verbal memory (Rey Auditory Verbal Learning Test) and a cognitive screening tool (Montreal Cognitive Assessment). Thedegree of impairment was not severe, because it did not reach very low scores, but it was consistently low. Moreover, participants with chronic migraine also tend to present more cognitive complaints that those with episodic migraine on a Perceived Deficits Questionnaire. These results thus indicate that chronic migraine is associated to cognitive dysfunction, even between acute attacks, which enlarges the spectrum of difficulties reported by these patients. Such data have clinical and research implications. First,it means that one must not overlook the cognitive complaints reported by patients with chronic migraine, considering they may correspond to an objective lower cognitive performance. Second, it raises the question of the temporal, and eventually causal, relation between migraine chronification and cognitive dysfunction (which comes before or after) and its long-term outcome, namely its reversibility and impact on age-associated decline. Third, in methodological terms, it means that one needs to separate 132 Arq Neuropsiquiatr 2020;78(3):131-132 chronic from episodic migraine populations in any cognitive study. In fact, although most studies did not associate episodic migraine with interictal dysfunction16,17, one of the studies stating the opposite included 20% of patients with chronic migraine18, which may have introduced a bias in the results. The current report study does not allow to answer these questions and more studies will be needed. 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