Both migraine and epilepsy are heterogeneous families of chronic disorders with highly variable clinical features, natural histories, and patterns of treatment response.1,2 Both are characterized by episodes of neurologic dysfunction, sometimes accompanied by headache, as well as gastrointestinal, autonomic, and psychological features. Each has an internationally recognized classification system.3
The International Headache Society (IHS) criteria divide headache disorders into two main groups, with similarities to groups of epilepsies:3
- Secondary headaches, symptomatic of an underlying condition such as trauma or a mass lesion. This group is analogous to the symptomatic epilepsies.
- Primary headaches, with no identifiable underlying cause. This group includes migraine, tension-type headache, cluster headache, and a number of rare disorders; it is analogous to the idiopathic epilepsies.
The following pages focus on the relationship between headache (especially migraine) and epilepsy for several reasons:
Migraine and epilepsy are highly comorbid.
Individuals with one disorder are at least twice as likely to have the other.1,4–7 Comorbid disease presents challenges in both differential diagnosis and concomitant diagnosis.8 When diseases are comorbid, the principle of diagnostic parsimony does not apply. Individuals with one disorder are more likely, not less likely, to have the other.
In the Epilepsy Family Study, among probands with epilepsy who were classified as having migraine on the basis of their self-reported symptoms, only 44% reported physician-diagnosed migraine.91 In the general population, 29% of men and 40% of women with migraine reported a medical diagnosis.12 The proportion of probands reporting a physician’s diagnosis of migraine was surprisingly low, given that all were already being treated for epilepsy.
Why is the comorbidity of migraine and epilepsy not recognized? Epilepsy may be viewed as a more serious disorder than migraine. As a result, the migrainous symptoms of patients with a diagnosis of epilepsy may have been overlooked or attributed to the seizure disorder.
The clinical presentation may overlap, creating diagnostic difficulty.
In typical patients, the clinical history usually allows the separation of migraine and epilepsy. The diagnosis of atypical migraine symptoms can be quite difficult, however, and a number of epileptic and nonepileptic syndromes may mimic migraine. In more complex cases, EEG and video-EEG monitoring are useful. Because migraine and epilepsy are associated, clinicians should be sensitive to the issue of concomitant diagnoses.
Risk factors, mechanisms, and treatments overlap.
Some patients with epilepsy and migraine may not report their headaches because the headaches are being effectively treated with an antiepileptic drug without a diagnosis of migraine. On the other hand, the interview used in the Epilepsy Family Study may lead to the over-diagnosing of migraine in some patients.
Because of its greater prevalence, migraine is common in people with epilepsy, whereas epilepsy is rare in migraineurs. The diagnosis and treatment of each disorder must take into account the potential presence of the other.8
Adapted from: Silberstein, SD, and Lipton RB. Headache and epilepsy. In: Ettinger AB and Devinsky O, eds. Managing epilepsy and co-existing disorders. Boston: Butterworth-Heinemann; 2002;239–254.
With permission from Elsevier (www.elsevier.com).