Drop in Blood Oxygen Level Could Explain Sudden Death in Epilepsy Patients

A new study suggests that the Sudden Unexpected Death in Epilepsy (SUDEP) of some patients may be a result of their brains not signaling the body to breathe during seizures, due to a lack of Oxygen in the blood.

Researchers at the University of California (UC) Davis Medical Center (USA) conducted a retrospective study and examined the medical records detailing 300 seizures in 57 epilepsy patients with chronic, recurrent, unprovoked seizures to examine the reason for deaths of epileptics that could not be explained by repeated convulsive seizures, accidents, or other mishaps. They then compared patients with severe convulsive seizures to those with milder symptoms such as transient confusion, lip smacking, and head turning.

The study results showed that one-third of all seizures were associated with hypoxemia, with drops in blood-oxygen (SpO2) levels below 90%. In 12% of these patients, blood-oxygen levels actually dropped below 70% during the seizure. The researchers also found that seizures in the temporal lobe of the brain were more often associated with significant drops in SpO2 levels, and that males were more likely than females to experience dangerously low levels of oxygen during seizures. The researchers suggest that the findings support the idea that some cases of SUDEP may be caused by a lack of brain signaling that makes the patient continue breathing, and recommend that hospitals that monitor inpatients for seizures should use both continuous SpO2 monitoring as well as and around-the-clock monitoring by staff or relatives. The study was published online in the October 24, 2008, issue of the journal Brain.

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

In a hospital setting, SpO2 levels below 85% require intervention, such as giving supplemental oxygen, turning the patient on his side, or suctioning of the patient's airway to help him breathe. Some medical centers also use video monitors that are continuously observed by hospital staff.

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University of California (UC) Davis Medical Center