Drops in blood oxygen levels may be key to sudden death in some epilepsy patients

November 17, 2008

(SACRAMENTO, Calif.) -- A new study by researchers at UC Davis Medical Center suggests that the sudden unexplained deaths of some epilepsy patients may be a result of their brains not telling their bodies to breathe during seizures.

"Significant drops in blood oxygen levels are more common than we thought in patients with partial seizures," said study senior author Masud Seyal, a professor of neurology at UC Davis Medical Center and director of the UC Davis Comprehensive Epilepsy Program.

The study, published online in the Oct. 24 issue of the journal Brain, studied Sudden Unexpected Death in Epilepsy, what doctors call SUDEP for short, to examine deaths of epileptics not explained by repeated convulsive seizures, accidents or other mishaps.

"What we've known for a long time is that SUDEP appears to be the most important cause of increased mortality in epilepsy patients. What we haven't known is what causes it," Seyal said.

The findings suggest that some cases of SUDEP may result from the brain not signaling the patient to continue breathing during seizures, though more conclusive evidence is needed, he said.

"It may have to do with an abnormal heart rhythm or it just may be that the brain stops sending the proper signals to maintain normal breathing," Seyal said.

In the retrospective study, Seyal and his colleagues examined records of 300 seizures in 57 epilepsy patients with chronic, recurrent, unprovoked seizures. They compared patients with severe convulsive seizures to those with milder symptoms like transient confusion, lip smacking and head turning.

One-third of all seizures were associated with drops in blood-oxygen levels below 90 percent. Seyal said he was surprised to find that 12 percent of these patients' blood oxygen levels actually dropped below 70 percent during their seizures.

They also discovered that seizures in the temporal lobe of the brain are more often associated with significant drops in blood-oxygen levels and that males are more likely than females to experience dangerously low levels of oxygen during seizures.

The findings support the idea that some cases of SUDEP may be caused by a lack of brain signaling that makes the patient keep breathing, though scientists need to do more research before they know for sure, Seyal said.

The study is important, Seyal said, because it suggests that hospitals that monitor inpatients for seizures should use both continuous blood-oxygen monitoring that sets off alarms when blood levels are too low and around-the-clock monitoring by staff or relatives.

In a hospital setting, blood-oxygen levels below 85 percent require intervention, such as giving supplemental oxygen, turning the patient on his side or suctioning the patient's airway, to help the patient breathe.

Patients hospitalized for seizure monitoring in the UC Davis Comprehensive Epilepsy Program must have a relative or friend with them around the clock who can recognize their seizures and summon assistance when they occur, in addition to constant blood-oxygen monitoring.

Some medical centers also use video monitors that are continuously monitored by hospital staff. But many do not employ this kind of close monitoring.

"Our data show that it's important that respiratory parameters be closely monitored in the hospital," Seyal said.

The best strategy to reduce the likelihood of SUDEP is to promptly and effectively control patients' seizures, Seyal said.

Most seizures can be stopped with medication. Patients with seizures poorly controlled with medication often are candidates for surgery, which can have a high success rate. To perform the surgery, however, patients must be observed in the hospital, their medication must be reduced and seizures allowed to take place.

"This is the only way we can pinpoint the region of the brain responsible for the seizures and know where to operate," he said.

Seyal and his colleagues are working to determine the best ways to deal with patients who have severe drops in oxygen levels with seizures.

"The important thing here is to see how we can intervene to deal with the hypoxemia when it happens," he said.
-end-
Other UC Davis study authors include Lisa Bateman, assistant professor of neurology and Chin-Shang Li, associate professor of public health sciences. Data analysis for the study was partially funded by grants from the National Institutes of Health (NIH).

UC Davis Medical Center is the leading referral center in the region for the most seriously injured or ill patients and the most medically complex cases, covering 33 counties, more than 65,000 square miles and 6 million residents. It operates inland Northern California's only Level 1 trauma center, with comprehensive adult and pediatric emergency departments. The center has been instrumental in keeping Sacramento County's preventable death rate at or below 1 percent, which is less than half the national average. Studies show patients with specific critical injuries have better survival rates and functional outcomes at Level 1 trauma centers and academical medical centers. For more information, visit www.ucdmc.ucdavis.edu.

University of California - Davis Health System

Related Epilepsy Articles from Brightsurf:

Focal epilepsy often overlooked
Having subtler symptoms, a form of epilepsy that affects only one part of the brain often goes undiagnosed long enough to cause unexpected seizures that contribute to car crashes, a new study finds.

Antibodies in the brain trigger epilepsy
Certain forms of epilepsy are accompanied by inflammation of important brain regions.

Breaching the brain's defense causes epilepsy
Epileptic seizures can happen to anyone. But how do they occur and what initiates such a rapid response?

Using connectomics to understand epilepsy
Abnormalities in structural brain networks and how brain regions communicate may underlie a variety of disorders, including epilepsy, which is one focus of a two-part Special Issue on the Brain Connectome in Brain Connectivity, a peer-reviewed journal from Mary Ann Liebert, Inc., publishers.

Epilepsy: Triangular relationship in the brain
When an epileptic seizure occurs in the brain, the nerve cells lose their usual pattern and fire in a very fast rhythm.

How concussions may lead to epilepsy
Researchers have identified a cellular response to repeated concussions that may contribute to seizures in mice like those observed following traumatic brain injury in humans.

Understanding epilepsy in pediatric tumors
A KAIST research team led by Professor Jeong Ho Lee of the Graduate School of Medical Science and Engineering has recently identified a neuronal BRAF somatic mutation that causes intrinsic epileptogenicity in pediatric brain tumors.

Can medical marijuana help treat intractable epilepsy?
A new British Journal of Clinical Pharmacology review examines the potential of medicinal cannabis -- or medical marijuana -- for helping patients with intractable epilepsy, in which seizures fail to come under control with standard anticonvulsant treatment.

Fertility rates no different for women with epilepsy
'Myth-busting' study among women with no history of infertility finds that those with epilepsy are just as likely to become pregnant as those without.

Do women with epilepsy have similar likelihood of pregnancy?
Women with epilepsy without a history of infertility or related disorders who wanted to become pregnant were about as likely as their peers without epilepsy to become pregnant.

Read More: Epilepsy News and Epilepsy Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.