Monitoring Shows High Rate of Subclinical Seizures After Cerebral Hemorrhage

Pauline Anderson

December 28, 2010

December 28, 2010 (San Antonio, Texas) — Emerging epilepsy research highlights the importance of having a high level of suspicion when treating patients who have sustained a major cerebral insult, whether through cerebral hemorrhage or trauma.

One new study found that at least one quarter of patients in intensive care with a cerebral hemorrhage who underwent evaluation with continuous electroencephalography (cEEG) were diagnosed with subclinical seizures, mostly status epilepticus.

A second study showed that children with an acute brain injury had more than double the rate of early posttraumatic seizures (EPTS) of adults with similar injuries.

Both studies were reported here at the American Epilepsy Society 64th Annual Meeting.

Strong Argument for Continuous Monitoring

For the first study, researchers from the Northeast Regional Epilepsy Group and the Atlantic Neuroscience Institute reviewed the records of more than 1000 patients with cerebral hemorrhage including intracerebral hematoma, subarachnoid hemorrhage, or subdural hematoma admitted consecutively to the Neuro-ICU at Overlook Hospital in Summit, New Jersey. Of these patients, 20% underwent continuous EEG evaluation, and only a few had routine EEGs.

Of the patients who had EEGs, 25.3% had periodic discharges and/or seizure activity. In almost all cases, seizure activity was subclinical and compatible with a diagnosis of status epilepticus.

"The overwhelming majority of patients who had seizure activity were having subclinical or nonconvulsive seizures; in other words, this isn't something you can see with the naked eye," said lead investigator Jeffrey M. Politsky, MD, director, Research, Northeast Regional Epilepsy Group, and medical director Atlantic Neuroscience Institute Comprehensive Epilepsy Center, also in Summit.

The prevalence of any sort of epileptiform activity was 40.4%.

Because continuous seizure activity is harmful to the brain and patients with cerebral hemorrhage already have an injury to the brain, the study results strengthen the argument that these patients should be evaluated for subclinical seizure activity, said Dr. Politsky.

There was no significant difference in the prevalence of seizure activity among the different types of hemorrhage. Continuous EEG detected seizure activity in a much higher percentage of patients than did routine EEG.

As more than 700 patients with cerebral hemorrhage did not undergo EEG evaluation, the diagnosis of subclinical seizures may have been missed in more than 200 cases since the review began in 2007, said Dr. Politsky.

2 Strikes

Since making a similar presentation earlier this year at the American Academy of Neurology annual meeting in Toronto, Dr. Politsky has added "almost a year's worth of data." Over that period, the prevalence of subclinical seizures has increased.

"As the data accumulates, we are actually confirming and strengthening the argument that patients who have cerebral hemorrhage really deserve to be evaluated for subclinical seizure activity and status epilepticus," he said. "Now virtually all patients with this diagnosis undergo at least 24 hours of cEEG: due to the high prevalence of seizure activity, the diagnosis of subarachnoid hemorrhage, subdural hematoma, and intracerebral hematoma is an indication for evaluation.

"Some EEG patterns are initially indeterminate, and we follow the EEG for an additional period of time — in many cases, seizure activity develops several days after presentation," he added.

He stressed that these patients already have an insult to the brain, whether blood is present in the brain tissue or in the layers around the brain. "They're already compromised neurologically, so if they also happen to have subclinical seizures or status epilepticus, that's 2 strikes, and if it goes on for a prolonged period of time, we would imagine that this would contribute very negatively to prognosis and outcome."

To determine whether this is the case, Dr. Politsky plans to follow-up the patients in his study who were diagnosed and treated for subclinical seizures and compare their outcomes with those patients who were not diagnosed with such seizures.

Children at Risk

The second study included 27 children with moderate to severe traumatic brain injury who were admitted to Denver Children's Hospital during a 9-month period. The researchers reported that 55.5% of the children had EPTS, which is higher than the rate previously reported in a similar study of 94 adults (Vespa et al, 1999), 22.3% of whom had EPTS.

The rate was even higher among children experiencing nonaccidental trauma (84.6%).

"We know that children have a high rate of early posttraumatic seizures when they have moderate or severe injuries, but this rate of 56% is even higher than what has been shown in past clinical studies," said lead investigator Daniel Arndt, MD, director of the Pediatric Epilepsy Program at DeVos Children's Hospital, Grand Rapids, Michigan.

"That's because we identified a fair number of seizures with EEG. Roughly 20% of children had seizures that were detected by EEG only; these would never have been noticed without EEG," he noted.

Although the study was small, its results suggest that it might be prudent for all children with head injuries to be monitored with EEG to detect subclinical seizures, said Dr. Arndt.

The children in the study ranged in age from 1 month to 16 years. Causes of their brain trauma included motor vehicle accidents, falls, blunt injury, and nonaccidental trauma (ie, shaken baby syndrome). Once in the pediatric intensive care unit, they had continuous EEG for 48 hours.

The researchers observed the children for clinical seizures and used the EEG data to capture subclinical episodes occurring within 7 days of the injury.

The study showed a high rate (44.4%) of status epilepticus that was often subclinical. The rate of epileptiform discharges was 5-fold higher in children than among the adults studied previously (50% vs 10%).

Children younger than 2 years and those subjected to nonaccidental trauma were most susceptible to these early seizures.

The study was the first to look at EPTS other than retrospectively, said Dr. Arndt. "This study is unique in that it has EEG running, so it's going to accurately identify seizures looking forward from the time that they're monitored until the monitoring stops."

Hot Topic

Whether to treat these subclinical seizures captured through EEG is a "hot topic," said Dr. Arndt. In the past, many experts believed that these seizures were not harmful and did not need treatment. However, more recently, laboratory and preclinical data have shown worsened morbidity and outcomes associated with these seizures. "Most epileptologists — most neurologists — are now treating EEG only seizures, especially status epilepticus, especially in children, and especially if they're acute."

Although EPTS did not influence the short-term outcome measures of intensive care unit/hospital length of stay and duration of intubation of the patients in this study, Dr. Arndt said outcome scale scores and measures sometimes do not reflect changes until at least a year.

The next step for their group is to pool the results of this study with those of a similar study at the University of California–Los Angeles, which should provide a patient population comparable with the earlier adult study. He hopes in future to also develop a multicenter study.

Asked to comment on these 2 studies, Maria Sam, MD, associate professor of neurology at Wake Forest Baptist Medical Center, Winston Salem, North Carolina, and a member of the American Academy of Neurology, said that although both studies were small, the preliminary data are "very useful" and "heralds a new era" in intensive neurological monitoring.

"We have had similar experiences in our medical center with children with a history of head trauma — all types — and adults with intracranial hemorrhage," Dr. Sam said in an email to Medscape Medical News. "Although the numbers are small, our practice has seen improved outcomes for those patients who have subclinical seizures treated after a major cerebral insult."

In the past, many patients who remained in a coma after a major cerebral insult likely were in subclinical status that went undiagnosed, she said.

American Epilepsy Society 64th Annual Meeting: Abstract 1.067; Platform C.05. Presented December 3 - 4, 2010.

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