Like stroke and depression, migraine and epilepsy have a well-documented association. Individuals with migraine or epilepsy are more than twice as likely to have the other condition. While the prevalence of epilepsy in the general population is only 0.5 to 1 percent, in migraineurs it is about 5.9 percent. Similarly, the Epilepsy Family Study of Columbia University found that 24 percent of people with epilepsy have been found to have migraines, compared with only 12 percent of the general population.
It has been found that the age of first seizure is unrelated to the risk of developing migraines, suggesting that migraines are not solely responsible for epilepsy and also not the sole result. It is possible that there are subtle alterations in brain chemistry, such as lower levels of magnesium, changes in neurotransmitter levels, or other possible complex biological factors that could simultaneously increase the risk of both migraine and epilepsy.
Despite being distinct conditions, epilepsy and migraine share a surprising number of commonalities. They are both episodic, chronic, neurological disorders. A 2005 study in the journal
Altered consciousness is also a common symptom between the two conditions; it is found only in rare subtypes of migraines but takes place in about 40 percent of seizures. Even headache, which might seem to indicate a migraine by definition, is not a definitive diagnostic tool. The 2005 study reports that up to 20 percent of migraine auras may occur in isolation from a headache, while as many as 19 percent of patients with epilepsy report a headache during the course of, or following, a seizure.
The study suggests that electroencephalography (EEG) may be one of the few ways to quantitatively distinguish between an epileptic seizure and a migraine when they share these common manifestations.
In a migraine, the EEG usually appears normal, though some focal slowing may be present. During a seizure, however, the EEG usually shows a typical seizure pattern, although simple partial seizures may be mild enough not to have a diagnostic seizure pattern easily visible on the EEG. Therefore, while EEG is a useful tool to distinguish between some migraines and seizures, it is not completely reliable.
Since migraine and epilepsy are comorbid and often occur together, techniques like EEG may be necessary to supplement a clinical diagnosis. EEG is a common tool used to diagnose epilepsy but is rarely used on migraineurs.
In addition to having some similar characteristics, migraine and epilepsy are also frequently found together in the same patient. For example, one migraine variation, familial hemiplegic migraine, is often associated with epilepsy, although the manifestation of each is different enough to allow separate diagnoses. As in other migraine comorbidities, it is often advantageous to the patient to find a drug that can treat both migraine and epilepsy simultaneously.
Other neurological problems are sometimes comorbid with migraines, and can have similar treatments to epilepsy. For example, the treatments described for epilepsy are often also effective for patients who have bipolar or manic depressive illness as well as a prophylaxis for migraines.
Some drugs primarily intended to treat epilepsy have shown to be very effective in treating migraines as well. Divalproex sodium (Depakote) and topiramate (Topamax) are indicated by the FDA as effective in treatment for both epilepsy and migraines. Chapter 8 has more information on antiepileptic drugs, or AEDs, used to treat migraine.