Seizures (brief episodes of abnormal electrical activity in the brain) and migraines (severe headaches often accompanied by neurological symptoms like aura) share a complex, intertwined relationship. This connection is not always simple, as it involves both direct causation and frequent co-occurrence. The link stems from shared biological pathways that make the brain susceptible to both paroxysmal events. Understanding this relationship requires examining how one event can follow the other and the underlying vulnerabilities that predispose an individual to both conditions.
Headaches Following Seizures (Postictal Phenomenon)
One direct causal link is the headache that frequently occurs immediately after a seizure, known as a postictal headache. This phenomenon is common, affecting 30% to 50% of adults who experience epileptic seizures. These headaches typically begin within three hours of the seizure ending and resolve spontaneously within 72 hours.
While many postictal headaches resemble tension headaches, a significant portion exhibits migrainous features. These features include a throbbing quality, moderate to severe intensity, and sensitivity to light and sound. The proposed mechanism involves the massive metabolic and physiological changes that occur as the brain recovers from the intense electrical discharge of a seizure.
The seizure causes a rapid depletion of neurotransmitters and significant fluctuations in cerebral blood flow. Initially, blood flow increases, followed by a prolonged period of reduction. This fluctuation is thought to activate pain-sensitive pathways in the brain. This cascade of neurochemical and vascular changes explains why a seizure can manifest as a headache that sometimes mirrors a migraine attack.
Migraine as a Potential Seizure Trigger
The reverse relationship, where a migraine provokes a seizure, is less common but still occurs. A severe migraine attack, particularly one with a prominent aura, can occasionally trigger a seizure, especially in individuals predisposed to epilepsy. The International Classification of Headache Disorders (ICHD-3) classifies this specific sequence as a “migraine aura-triggered seizure.”
The underlying mechanism for this triggering is Cortical Spreading Depression (CSD). CSD is a slow-moving wave of intense neuronal and glial depolarization that travels across the brain’s gray matter. It is considered the physiological basis of the migraine aura. This wave involves a massive redistribution of ions and a temporary suppression of electrical activity.
In a brain prone to seizures, the hyperexcitability caused by CSD lowers the seizure threshold. As the CSD wave spreads, it creates an environment where brain tissue is more susceptible to generating the uninhibited electrical discharge characteristic of a seizure. If a seizure occurs, it typically happens during the aura phase or within an hour of its onset.
Shared Vulnerability and Co-occurrence
Beyond immediate causal links, a deep connection exists as comorbidity, meaning the two conditions frequently co-occur without one acutely causing the other. Individuals with epilepsy are substantially more likely to experience migraines compared to the general population. Studies show they are nearly twice as likely to suffer from migraine headaches, pointing to a shared underlying vulnerability in brain biology.
This shared susceptibility often traces back to genetic factors affecting ion channels in nerve cells. These channels regulate the flow of charged particles (ions) across the cell membrane, determining neuronal excitability. Mutations in genes coding for these ion channels can lead to a generally hyperexcitable brain. This predisposition affects both the electrical storm of a seizure and the neurovascular instability of a migraine.
Family studies provide evidence for a strong genetic basis linking the two conditions, especially migraine with aura and epilepsy. The shared genetic and neurobiological foundations also involve dysregulation of neurotransmitter systems like serotonin and glutamate. These factors create a single spectrum of brain excitability disorders, explaining why many individuals experience both conditions independently.
Conditions Where Seizures and Migraines Overlap
In certain rare clinical syndromes, the distinction between a migraine and a seizure becomes blurred. An “epileptic headache,” also called an “ictal epileptic headache,” is a condition where the headache itself is the primary manifestation of seizure activity. The headache, which can be throbbing or sharp, is present during the seizure and resolves when the seizure ends.
A rare variant is hemicrania epileptica, characterized by a headache on the same side of the head as the epileptic discharge. The term “migraine aura-triggered seizure” describes the acute situation where a migraine aura directly precipitates a seizure. Although the older term “Migralepsy” is sometimes used, the clinical community favors the more precise ICHD-3 classification to avoid confusion.
These specific overlapping conditions require precise diagnosis, often involving electroencephalography (EEG), to confirm the electrical nature of the event. Correctly identifying the relationship is important for treatment. Treatments aimed at preventing seizures, such as anti-epileptic medications, are often effective in preventing migraines, and vice versa, underscoring their intertwined nature.