A stroke can cause a seizure. This is a recognized complication that arises when the sudden disruption of blood flow damages brain tissue. A stroke occurs when a blood vessel in the brain is blocked (ischemic stroke) or bursts (hemorrhagic stroke), leading to the death of brain cells. A seizure, in contrast, is an abrupt, abnormal surge of electrical activity within the brain’s neural networks. The injured brain tissue can become electrically unstable, creating a focus for these disorganized electrical bursts.
Understanding Neural Instability After a Stroke
The initial injury from a stroke, whether a lack of blood flow or bleeding, results in the death of neurons in the central lesion area. This neuronal loss triggers a complex repair process involving glial cells, specifically astrocytes, which respond to the trauma. The astrocytes proliferate and become hypertrophic, forming a dense barrier around the damaged area to contain the injury and protect the surrounding healthy tissue. This boundary is known as the gliotic scar, and while it is protective by sealing off the lesion, it is also electrically dysfunctional.
The formation of this scar tissue fundamentally alters the local environment and communication between surviving neurons at the border of the infarct. Healthy brain function relies on a delicate balance between excitatory signals and inhibitory signals. The presence of the gliotic scar and the surrounding inflammation disrupts this balance, often leading to a state of hyperexcitability. This shift toward excitation means the surviving neurons are more prone to firing excessively and synchronously, which is the underlying physical precursor for a seizure.
The physical location and type of stroke significantly influence the risk of developing this electrical instability. Strokes that affect the cerebral cortex carry a much higher seizure risk than those located deep within the brain structure. Hemorrhagic strokes, which involve bleeding, also tend to have a higher incidence of seizures compared to ischemic strokes. This is likely due to the greater inflammation and tissue distortion caused by the presence of blood within the brain tissue.
Seizure Timing Acute Versus Remote
The time elapsed between the stroke event and the first seizure has significant implications for prognosis and treatment. Acute symptomatic seizures occur within the first seven days following the stroke event. These seizures are generally considered a consequence of the brain’s immediate response to injury, driven by transient factors like acute swelling, inflammation, bleeding, or metabolic changes.
Because these acute seizures are provoked by temporary disturbances, they do not necessarily indicate a long-term risk of epilepsy. The underlying brain tissue is still highly unstable and undergoing rapid changes during this first week. Therefore, a person experiencing an acute seizure may not require long-term anti-seizure medication.
Remote symptomatic seizures, by contrast, are those that occur after the first seven days post-stroke. These seizures are typically unprovoked and are strongly associated with the stable, permanent changes to brain structure, particularly the fully formed gliotic scar tissue. When a person experiences repeated remote seizures, they are diagnosed with post-stroke epilepsy. This diagnosis carries a high risk of seizure recurrence because the underlying cause is a persistent anatomical and electrical abnormality.
Diagnosis and General Management
When a seizure is suspected following a stroke, a systematic approach is used to confirm the diagnosis and determine the cause. Clinical observation is paramount, as the physician needs to gather a detailed account of the event from witnesses to differentiate a seizure from other post-stroke conditions. Brain imaging, such as computed tomography (CT) or magnetic resonance imaging (MRI), is used to visualize the stroke lesion, confirming its location and size, which helps to assess the seizure risk.
The most definitive diagnostic tool for confirming abnormal electrical activity is the electroencephalogram (EEG). This test involves placing electrodes on the scalp to record the brain’s electrical signals, which can reveal the characteristic synchronized, excessive neuronal firing patterns associated with seizures. An EEG is especially useful in identifying seizures that do not involve noticeable convulsive movements.
The general management strategy for post-stroke seizures depends heavily on the timing and recurrence of the events. For acute symptomatic seizures, long-term anti-epileptic drugs (AEDs) are often not recommended, as the seizure risk may resolve as the brain stabilizes. Short-term treatment may be used in cases of multiple acute seizures or status epilepticus. For a diagnosis of post-stroke epilepsy, long-term AED therapy is typically initiated. The goal of this treatment is to control the seizures and minimize side effects.