A stroke occurs when blood flow to a part of the brain is interrupted, either by a blocked artery (ischemic stroke) or the rupture of a blood vessel (hemorrhagic stroke). This disruption deprives brain cells of oxygen and nutrients, leading to damage. A recognized complication of stroke is the occurrence of seizures.
The Link Between Stroke and Seizures
A stroke can lead to seizures through several interconnected mechanisms within the brain. When a stroke damages brain tissue, it disrupts the normal electrical signaling between nerve cells. This damage can create an unstable electrical environment, making the brain more prone to abnormal bursts of electrical activity that characterize a seizure.
Following a stroke, inflammation occurs in the affected area. This neuroinflammation can contribute to neuronal hyperexcitability, increasing the likelihood of seizures. Over time, damaged brain tissue can form scar tissue, a process known as gliosis. This glial scar tissue can become an epileptic focus, meaning it acts as an irritable area that generates abnormal electrical discharges.
The specific location and severity of the stroke are significant factors influencing seizure risk. Strokes affecting the cerebral cortex, the outer layer of the brain, carry a higher risk. Hemorrhagic strokes are also associated with a greater likelihood of post-stroke seizures compared to ischemic strokes.
Types and Timing of Post-Stroke Seizures
Post-stroke seizures are categorized based on their timing relative to the stroke event. Early post-stroke seizures occur within the first week following the stroke, often within the first 24 hours. These seizures are a direct result of the acute brain injury, including metabolic and physiological disturbances or inflammation. About 2% to 33% of stroke patients experience early seizures.
Late post-stroke seizures develop more than a week after the stroke, sometimes months or even years later. These seizures are often linked to the development of post-stroke epilepsy, defined by recurrent unprovoked seizures. The formation of glial scar tissue and chronic changes in brain circuitry are thought to underlie late seizures. The risk of late seizures varies.
Seizures after a stroke can manifest in different ways. Focal seizures, also known as partial seizures, originate in the brain region affected by the stroke. Symptoms can vary, ranging from localized muscle twitches or sensory changes to confusion or altered awareness. These focal seizures can sometimes spread to affect both sides of the brain, becoming secondarily generalized seizures, leading to symptoms like muscle spasms and loss of consciousness. Generalized seizures, involving widespread electrical activity across both brain hemispheres, can also occur, causing full-body muscle spasms and loss of consciousness.
Identifying and Managing Post-Stroke Seizures
Identifying post-stroke seizures involves careful clinical observation of symptoms, as well as diagnostic tests. An electroencephalogram (EEG) is a primary tool used to detect abnormal electrical activity in the brain, which can confirm a seizure diagnosis. Brain imaging, such as MRI or CT scans, is also used to assess the extent and location of stroke damage and to rule out other potential causes of seizures.
Managing post-stroke seizures begins with a medical consultation to determine the appropriate course of action. Not all seizures after a stroke necessitate long-term medication, especially if it is an isolated early seizure. However, anti-seizure medications are often prescribed, particularly for recurrent seizures or if epilepsy develops. Common medications include levetiracetam and lamotrigine.
Lifestyle adjustments and safety precautions are also important for individuals experiencing seizures. This includes steps to prevent injury during a seizure, such as avoiding activities where a sudden loss of consciousness could be dangerous. Prophylactic use of anti-seizure medications to prevent seizures is generally not recommended due to potential side effects and lack of strong evidence for benefit. Decisions regarding medication, including when to start or discontinue treatment, are individualized and made in consultation with a neurologist.