As if a stroke weren't enough to overcome, patients who survive strokes are more likely to have seizures. The risk of seizure after ischemic stroke is at least 5%, according to recent research, while hemorrhagic strokes entail even greater risk of one or more subsequent seizures.
Yet seizures and epilepsy after stroke are generally under-recognized by physicians, according to experts. The seizures may be missed because they may not look like typical seizures and can resemble stroke symptoms or because stroke patients have difficulty communicating about their symptoms.
However, the experts also say that there are signs, symptoms, and risk factors that physicians can use to predict the possibility of developing epilepsy after stroke.
Poststroke seizures have heterogeneous presentations, depending on what part of the brain is affected, according to Kara Sands, MD, a neurologist at Mayo Clinic in Phoenix. Consequently, they don't necessarily look like the generalized tonic-clonic seizure that most people envision when they hear the word “seizure.”
“One patient's seizure may present with limb posturing or abnormal movements, while another's might do so as clumsiness or a fall,” she said.
In addition, seizures are considered stroke mimics, explained Dr. Sands. As a result, even the most trained and experienced physician will sometimes have a tough time differentiating between the two, she noted.
When the clinician examines a patient can make a difference, said Dr. Sands. The diagnosis of seizure is much simpler if a physician enters a patient's room as he is rhythmically jerking in the midst of an active seizure event, as opposed to when he is sleeping soundly after the event has occurred, she explained.
Another challenge is that following a stroke, some patients are unable to verbalize their symptoms, which family members might fail to recognize as well, according to Archie Ong, MD, a neurologist at NorthShore University HealthSystem in Evanston, Ill.
These factors combine to make the seizures easy to overlook. “If a seizure is a convulsion, that, of course, would be obvious. But subtle seizures can occur and if the patient is unable to report them, they could go unnoticed,” said Roy Sucholeiki, MD, a neurologist at Northwestern Medicine Central DuPage Hospital in Winfield, Ill.
Poststroke epilepsy can also be missed because clinicians are focused on more urgent issues at first. “The priority is addressing the life-threatening or severe disabling nature of the illness,” said Dr. Sucholeiki.
The experts did offer some strategies for identifying seizures in poststroke patients. “We look for any abnormal involuntary movements—which way the eyes are looking,” said Dr. Sands. “Typically, a seizure patient's eyes will be deviated away from the irritative seizure focus,” she said.
A stroke works the other way around: A patient's eyes will be looking in the direction of the side of the brain where the ischemia or bleeding occurred.
For example, if a patient were being treated for a large ischemic stroke on the left side of the brain, “we'd expect his eyes to preferentially look to the left and have weakness on his right side and language problems,” said Dr. Sands.
If, years later, the same patient came to the ED with similar signs or symptoms, like right-sided weakness or abnormal movement or language troubles, but his eyes were looking to the right, a physician should be suspicious of seizure, she added.
Any paroxysmal movements, including twitching or jerking, eye deviation, or apparent alteration of awareness, are some signs that may raise suspicion for seizure, added Jennifer Hopp, MD, an associate professor of neurology at the University of Maryland School of Medicine and director of the epilepsy division at University of Maryland Medical Center in Baltimore.
To assess, use focused questions, such as whether a patient has experienced any blackouts or episodes of losing time or has been awakened with a tongue bite or incontinence in the morning, which could suggest an unwitnessed generalized tonic-clonic seizure, said Dr. Hopp. Another good question is whether a patient has uncontrolled jerking or twitching of an extremity, particularly on one side of the body, she noted.
After-effects of a stroke typically are static, while symptoms associated with seizures and epilepsy are more transient, the experts said.
Another difference is that seizures usually cause positive phenomena, such as movement, while strokes cause negative symptoms, like weakness, noted Nathan Fountain, MD, professor of neurology at the University of Virginia in Charlottesville and director of the Comprehensive Epilepsy Program.
To determine whether a patient has had a seizure, a neurologist would review the medical history, recent neuroimaging, and labs. In the event of any suspicion for seizure activity, an electroencephalogram would be ordered to look for any abnormalities suggestive of seizures.
There are also predictive risk factors. The greater the damage caused by the stroke, the more likely the development of poststroke epilepsy, researchers said. Brain damage from a stroke tends to be more extensive in younger patients and consequently the risk that they'll develop poststroke epilepsy is higher.
Poststroke epilepsy is also believed to be most likely after strokes in the cortical or outer layer of the cerebrum, especially with evidence of hemorrhaging, said Dr. Fountain. That's because blood is more likely to cause a seizure focus, whether it stems from an intracerebral hemorrhage or bleeding in an ischemic stroke. Conversely, small-vessel, subcortical, and lacunar strokes are unlikely to cause seizures.
Poststroke seizures are categorized based on how long they occur after a stroke. Acute symptomatic seizures are those that occur within the first two weeks of stroke, explained Dr. Hopp. Seizures that occur more than two weeks following an ischemic stroke, known as late-onset seizures, are considered a risk factor for the development of poststroke epilepsy, Dr. Sands said.
While the highest risk for poststroke epilepsy occurs in the first 30 days following a stroke, it also can begin years later, she added. “Once someone has an injury or scar on the brain, they're at increased risk of later experiencing a seizure,” Dr. Sands said.
No specific treatments are available to prevent the development of epilepsy after a stroke. Poststroke patients seem like an ideal population to study treatments that could prevent the development of epilepsy, since it's a well-defined group at risk for the condition, but no positive studies have been published, noted Dr. Fountain.
It might eventually be possible to identify high-risk patients who would benefit from prophylactic medication, according to Dr. Hopp. “Genetic biomarkers, or other surrogate markers of risk, may be useful to identify these patients,” she said.
In the meantime, educating patients, their families, and caregivers about the issue is essential, Dr. Sands observed. That way, they'll know warning signs and how to respond.
For example, patients at Dr. Ong's facility receive a stroke handbook that mentions the issue. “If they're educated on the topic, they're more aware about looking for it,” he said.
Dr. Sucholeiki agreed. “The patient, family, and caregivers must be counseled about this possibility. Fortunately, most instances of seizures are not life-threatening, but the risk of injury is high from falls that take patients by surprise. The good news is that epilepsy from stroke typically responds very well to treatments that are both safe and tolerable.”