A stroke occurs when blood flow to the brain is disrupted, either by a blockage (ischemic stroke) or a burst blood vessel (hemorrhagic stroke). This interruption deprives brain cells of oxygen, causing injury. Post-stroke seizures (PSS) are a complication resulting from this damage, representing a sudden, abnormal burst of electrical activity within the injured brain tissue. These seizures can occur at any time, from the moment of the stroke to years later. Understanding the risk and timing of these electrical disturbances is important for effective management.
How Often They Occur and When
The overall prevalence of post-stroke seizures is estimated to be around 10% among all stroke patients, making stroke the most common cause of seizures in older adults. However, the likelihood and long-term implications depend heavily on when the first seizure occurs relative to the stroke event. Seizures are broadly classified into two categories based on this timing: early and late.
Early seizures are defined as those that happen within the first seven days following the stroke. These acute symptomatic seizures affect approximately 2% to 16% of patients, with the majority occurring within the initial 24 hours. They are often triggered by the immediate injury, such as brain swelling, inflammation, or acute metabolic changes.
Late seizures occur more than seven days after the stroke and are associated with a higher risk of developing chronic epilepsy. These seizures develop in about 3% to 4% of survivors and often signify the formation of enduring scar tissue, making the brain prone to electrical misfiring. A single unprovoked late seizure is often enough for a diagnosis of post-stroke epilepsy (PSE). The recurrence risk for patients who experience a late seizure is often greater than 50%, compared to a much lower risk for those who only have an early seizure.
Factors That Increase Seizure Risk
Certain characteristics of the stroke significantly increase the likelihood of post-stroke seizures. The type of stroke is a major differentiator in risk. Hemorrhagic strokes, which involve bleeding, carry a higher risk (6% to 16% of patients). Ischemic strokes, caused by a blockage, have a lower associated risk (roughly 3% to 7% of patients).
The location of the brain injury is the most important predictor of seizure risk. Strokes that involve the cortex are significantly more likely to cause seizures than those in deeper brain structures. Cortical involvement is a primary risk factor for both early seizures and the development of long-term post-stroke epilepsy.
The severity and size of the injury also play a direct role in determining risk. Larger, more severe strokes are associated with a higher incidence of post-stroke seizures. For ischemic strokes, the presence of hemorrhagic transformation (bleeding within the blocked area) increases the risk of early seizures. Younger age is another factor linked to a higher risk of developing post-stroke seizures.
Recognizing the Signs of a Seizure
Seizures following a stroke do not always present as full-body shaking. Most post-stroke seizures begin as focal seizures, starting in the specific area of the brain damaged by the stroke. Focal seizures, sometimes called partial seizures, may involve only localized symptoms without loss of consciousness. Signs can include localized twitching in one arm or leg, strange tastes or smells, or sudden, inexplicable fear.
Focal seizures with impaired awareness might manifest as a person appearing dazed, confused, or staring blankly for a few minutes. They may also engage in repetitive, non-purposeful behaviors like lip-smacking or hand movements. A generalized seizure, which affects both sides of the brain, is more recognizable and can cause a loss of consciousness and full-body rhythmic shaking, known as a tonic-clonic seizure.
If a seizure is observed, focus on safety and observation. Gently ease the person to the floor and turn them onto their side to help with breathing. Clear any hard or sharp objects from the immediate area to prevent injury. Timing the event is important information for medical professionals. Emergency services should be called if the seizure lasts longer than five minutes, or if another seizure begins before the person recovers.
Treating and Managing Post-Stroke Seizures
The decision to treat a post-stroke seizure depends heavily on its timing and recurrence pattern. For a single seizure that occurs in the acute phase (within the first week), long-term anti-seizure medication (ASM) is generally not recommended. The seizure is often a symptom of the acute brain injury and swelling, and the risk of long-term epilepsy is lower. However, if an acute seizure is prolonged or does not stop on its own, short-acting medications are used to terminate the episode.
Long-term ASM therapy is typically reserved for individuals diagnosed with post-stroke epilepsy, meaning they have experienced recurrent late seizures. The goal of this chronic management is to prevent future seizures and improve the patient’s quality of life. Common ASMs used for this purpose include newer-generation drugs such as lamotrigine and levetiracetam.
The selection of a specific medication is often guided by minimizing potential interactions with other necessary stroke medications, such as blood thinners. While post-stroke epilepsy is a chronic condition, it is often manageable with these medications. A significant proportion of patients can achieve long-term seizure freedom through individualized treatment plans.