Pauline Anderson

March 08, 2012

March 8, 2012 (New Orleans, Louisiana) — It is not uncommon for children who suffer a stroke to develop epilepsy, and those who have seizures at the onset of the stroke are at particularly high risk, new research suggests.

The rates of epilepsy are also significantly higher than seen in adults after a stroke, the researchers report.

The new findings should encourage physicians to counsel families with a child who has had a stroke about the possibility of developing epilepsy, said lead researcher Christine Fox, MD, from the University of California, San Francisco.

"We really need to look at how early or late seizures are affecting outcomes for these children," Dr. Fox told Medscape Medical News.

The findings were presented here at the International Stroke Conference (ISC) 2012.

Confirmed Unprovoked Seizure

The retrospective, population-based study looked at children from birth to 19 years of age who were enrolled in the Kaiser Pediatric Stroke Study from January 1993 through December 2007. The analysis included 371 children with symptomatic ischemic and hemorrhagic stroke who survived to hospital discharge.

Researchers used clinical databases to identify seizures and record review to confirm a diagnosis of epilepsy. They used International League Against Epilepsy proposed guidelines which define epilepsy as a confirmed unprovoked seizure more than 30 days after a stroke.

Investigators used survival analysis to determine rates and predictors of epilepsy after stroke and adjusted for gender, age (neonatal versus later childhood, up to age 19 years), stroke subtype (ischemic versus hemorrhagic), outcome at hospital discharge, and acute seizures at the time of stroke.

Of the 371 stroke cases that survived to discharge, 110 were in the neonatal period and 261 were in later childhood; 226 were ischemic and 145 were hemorrhagic. At stroke ictus, 36% had an acute seizure, and 66% had a documented neurologic deficit at hospital discharge.

The study found that after a median follow-up of 4.5 years, poststroke epilepsy occurred in 89 subjects. "Seven of these children had a history of seizures prior to the stroke, so we excluded them from our analyses because we were primarily interested in the children who developed new seizures after stroke," Dr. Fox noted.

The average annual incidence of epilepsy was 6.4% (95% CI 5.2%, 8%), with a 5-year cumulative risk of 23% (95% CI 18%, 28%) and 10-year cumulative risk of 39% (95% CI 31%, 51%).

This compares with roughly a 7.5% cumulative risk at 5 years, and 23% at 10 years in adults, "so it’s much higher" in children, said Dr. Fox.

Although their definition of epilepsy included those with only a single seizure after a remote stroke, they analyzed the cohort again after excluding children who had been seizure free without medication for 6 months after that first episode. "If you exclude these children, the annual average incidence of epilepsy was now 4.5%, with a 5-year cumulative risk of 17% and a 10-year cumulative risk of 34% — so still relatively high," she said.

Predictors of epilepsy included neurologic deficit at hospital discharge and seizure at stroke ictus, but not gender or stroke subtype.

Predictors of Epilepsy After Stroke in Children

Factor Hazard Ratio 95% Confidence Interval P
Neurologic deficit at hospital discharge 1.7 1.001 - 2.7 < .0001
Seizure at stroke ictus 3.9 2.5 - 6.0 < .0001

In univariate analysis, children who had a stroke in the neonatal period, within the first 28 days of life, appeared to have an increased risk on the order of 70% developing epilepsy compared with those who had a stroke later in childhood, she said. But after adjusting for various demographic factors, "children who had a neonatal stroke were no more likely to develop epilepsy," she noted.

The study helps to pinpoint important risk factors for epilepsy after a stroke in children, said Dr. Fox, adding that current incidence estimates are from tertiary referral centers and vary widely.

Several possible scenarios may explain the increased poststroke epilepsy risk in children, Dr. Fox said. Although there is currently no evidence to support it, one suggestion is that the treatment the children received at the time of the stroke could influence later development of epilepsy.

"For example, if a child had a seizure at the stroke presentation, are they more likely to be treated with an anticonvulsant medication and could this be influencing the development of epilepsy?"

Another possibility — and this might be more important — is the location or size of the stroke, said Dr. Fox, a factor that they were not able to look at in this study.

"I wonder if the acute seizure is simply a marker for say, stroke severity, or that a part of the brain is more epileptigenic so it causes a seizure at the acute time period," she speculated. That long-term injury may also be more likely to cause epilepsy down the line.

"Those are definitely reasons for future study," she added.

The study was supported by an American Heart Association Scientist Development grant, and grants from the National Institute of Neurological Disorders and Stroke.

International Stroke Conference (ISC) 2012: Abstract 41. Presented February 1, 2012.

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