‘Very High’ Risk of Epilepsy 1 Year After Stroke

Patients who experience stroke have a “very high” risk of epilepsy 1 year later, new research shows.

Results from a large registry study reveals patients who experienced a severe intracerebral hemorrhage (ICH) had an almost 10% chance of developing epilepsy or status epilepticus in the first year after the event. The same risk was 8% for patients with severe acute ischemic stroke (AIS) and 5% for those with mild ICH.

Dr Mads Ebbesen

“The risk of epilepsy after stroke is very high, especially after hematomas and severe strokes,” Mads Ebbesen, MD, PhD candidate, Department of Neurology, Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark, told Medscape Medical News.

“Even though the risk decreases substantially with time, it continues to be significantly elevated, especially for those with the most severe strokes,” Ebbesen said.

The findings were presented at the American Epilepsy Society (AES) 2021 Annual Meeting.

Timing, Type, Severity

The link between stroke and epilepsy is well known, with previous research showing that up to half of epilepsy incidents that occur after age 60 are caused by stroke.

For the current study, researchers investigated the timing of post-stroke epilepsy and the association with stroke type and severity.

They used data from the Danish Stroke Registry, which includes information on stroke type (ischemic or hemorrhagic) and severity, as well as stroke risk factors. To identify epilepsy cases, the investigators used the Danish National Patient Registry.

The study included 88,119 adult Danish residents (53.4% men) with no history of epilepsy and who had a first stroke between April 1, 2004, and December 16, 2016. Mean age at the time of stroke was 69.8 years.

Of these participants, 7661 had had an ICH, 79,157 an AIS, and 10,301 a transient ischemic attack (TIA).

The primary outcome was a diagnosis of epilepsy or status epilepticus. Because early seizures may be a part of an acute stroke, the follow-up period began 14 days after stroke occurred.

Researchers estimated the cumulative incidence of epilepsy for each of the first 4 years following a stroke. They stratified this by stroke type and severity using the Scandinavian Stroke Scale. Scores of 0 to 15 were defined as “very severe,” 16 to 30 as severe, 31 to 45 as moderate, and 46 to 58 as mild.

Risk Even After 4 Years

Results showed 3483 patients were diagnosed with epilepsy during the first 4 years after stroke. The absolute risk for epilepsy was highest for patients with an ICH. The risk in the first year after a very severe ICH was 9.8% (95% CI, 7.8-11.7).

The risk was almost half that (5.1%) in patients with mild ICH (95% CI, 4.3-5.9). The risk was 7.8% (95% CI, 6.8-8.7) for patients with very severe AIS, and 1.3% (95% CI, 1.2-1.4) for those with mild AIS.

After a TIA, the risk for epilepsy in the first year was 0.81%. “Some of this risk may be due to subsequent strokes, but we didn’t specifically look into this,” said Ebbesen.

For all groups, the risk decreased in subsequent years after the stroke, but didn’t disappear altogether. For example, with very severe hematomas the risk was 2.3% in the fourth year.

“I was surprised that there was still a significant risk for epilepsy even after 4 years,” Ebbesen said. “Most prior studies have described onset of post-stroke epilepsy primarily within the first 2 years.”

Although the researchers did not examine the effect age, gender, or other demographic factors may convey, Ebbesen noted that previous studies have suggested a higher risk for epilepsy among younger patients with stroke.

He and his colleagues did not have the opportunity to assess epilepsy types, or where in the brain the seizures originated.

While this study did not investigate biological mechanisms, Ebbesen said it is possible scarring in the brain can send out abnormal electrical activity. In the case of hemorrhagic strokes, irritation from blood residue may lead to abnormal electric activity, he added.

“Be On the Lookout”

Commenting on the findings for Medscape Medical News, Jacqueline French, MD, professor, of New York University Langone Comprehensive Epilepsy Center in New York City, said the study provides “important information” for clinicians.

“They should be made aware of the high likelihood of seizures after stroke, especially hemorrhagic stroke, within the first year,” said French, who was not involved with the research.

“Physicians should tell at-risk patients and their families to be on the lookout for subtle episodes of unusual feelings or behaviors to ensure that seizures are not overlooked,” she added.   

American Epilepsy Society (AES) 2021 Annual Meeting: Abstract #1.373. Presented December 4, 2021.

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