Migraine and epilepsy: are they connected in any way?

Migraine and epilepsy: statistical overlap

Do people with migraines have a higher risk of epilepsy? And what about the other way around: Do people with epilepsy suffer from migraines more often? Are both of these things true? A British and Dutch research team conducted a comprehensive review of the existing data on the links between migraine and epilepsy. Looking at all the data from multiple studies with a total of 1.5 million participants, a clear pattern emerged. People with epilepsy were 52% more likely to also have migraines, compared to people without epilepsy. At the same time, people with migraines were 79% more likely to also have epilepsy.

Are there shared root causes?

The authors of the study believe genes may be part of the reason for the strong link. Over the years, scientists have discovered several genetic factors that show up in both conditions, suggesting close connections between them. Another possible connection lies in “cortical spreading depression” (CSD), a wave of electrical activity that moves across the brain during a migraine attack – and which may also play a role in epilepsy (see this article on CSD). When doctors examined patients’ brain activity more closely, they found evidence to support this theory. The hyperexcitability of certain areas of the brain underlying CSD, which is found in people with migraine, might also contribute to the processes resulting in epilepsy. If true, this would reveal a fundamental similarity between the two conditions.

If the evidence confirms that the same processes are involved in the development of migraine and epilepsy, it would mean that the two disorders share a common underlying process, or pathophysiology. There is another finding which supports this idea: people who have both migraine and epilepsy tend to experience more severe symptoms and a poorer prognosis than those with epilepsy alone.

A challenge for research

However, scientists going through the existing research papers noticed an issue. Most of the research results available so far are hard to compare because different studies use different methods to diagnose whether someone truly has migraine or epilepsy. As well as making it harder to compare results across studies, these differences make it hard to draw conclusions. So overall, there is not enough hard data to say if or how epilepsy and migraine are connected. This is an issue often pointed out by the authors of review papers in this and other areas. Future studies should use standardized methods and tools to provide a solid basis for comparisons and reliable results.

Is there a connection in terms of timing?

To understand more about possible overlaps between migraine and epilepsy, researchers have also looked at when headaches occur in relation to epileptic seizures, and vice versa. In one study with over 500 epilepsy patients, scientists asked when headaches occurred and what kind of headaches they were. Most participants had focal epilepsy, which affects around 400,000 people in Germany. In this form of epilepsy, a seizure starts in one part of the brain but can spread to the rest of it.

In more than three-quarters of participants (78%), the headaches occurred after the seizure. About 43% reported headaches between two separate seizures. “Postictal” headaches (occurring after a seizure) usually start within three hours and may last up to three days. Most are much shorter than that, however. The most common type of headache in this patient population was tension-type headache (around 35%). About 12% reported migraine attacks.

Why do migraines and epilepsy occur together?

Why is there a connection between the timing of migraine and epilepsy? Scientists don’t know for certain. So far, researchers can only point to possible mechanisms that might play a role in the underlying processes causing the diseases. It seems clear that, after a seizure, blood vessels in the brain widen, changing blood flow in the affected area. Researchers believe that this might help trigger a migraine attack.

Another clear connection is the aforementioned shared hyperexcitability in the brain’s cortex. This could mean that one event (a seizure or migraine) can trigger or increase the likelihood of the other. Some scientists also suspect that the trigeminal nerve, an important cranial nerve that supplies sensory information to large areas of the face, is involved. The trigeminal nerve has long been thought to play a major part in migraine attacks. Finally, there are probably genetic factors that contribute to both disorders – either as direct causes or as influences that make the brain more sensitive. One thing is absolutely clear: a great deal more research is needed in the decades ahead to gain a clear understanding of all the underlying connections.