Migraine, epilepsy, and psychiatric comorbidity

Several years ago, Deprez et al.¹ reported linkage of occipitotemporal lobe epilepsy and migraine with visual aura to chromosome 9q21-q22 in Belgian families. In this issue of Neurology®, Tikka-Kleemola et al.² revisit the 9q21-q22 locus, with linkage of visual migraine aura in 36 Finnish families. Is this a coincidence, or evidence for a migraine–epilepsy comorbidity gene?

Comorbidity is defined as the co-occurrence of 2 or more separate disorders more than expected by chance. The comorbidity of migraine and epilepsy highlighted in the article by Tikka-Kleemola et al. is well-established. The relationships between migraine and epilepsy can also be viewed as part of a clustered network of multiple comorbid neurologic and psychiatric conditions. Overlapping relationships among migraine, epilepsy, major depression, and suicidality have been identified in both cross-sectional and case-control or prospective studies.³ Cross-sectional studies show associations between anxiety disorders and both epilepsy and migraine.^4–7 Examination of such comorbidity clusters can illuminate shared pathophysiology, and can have profound implications for diagnosis, prognosis, and treatment.

There is strong evidence that the relationships among these comorbid disorders are bidirectional. Depression and suicidality are not only more frequent in prevalent epilepsy, they have been shown to precede the onset of seizures^8–10 and to occur more often than in controls following epilepsy onset.¹¹ The relationship between migraine and epilepsy is also bidirectional; the risk …