A new study by UCD researchers suggests that some epilepsy related deaths result from patients‘ brains not telling their bodies to breathe during seizures.
The finding could help identify a risk factor for Sudden Unexpected Death in Epilepsy SUDEP, a condition in which the reason for death is unknown and is not due to prolonged convulsive seizures or seizure-related accidents.
Seizures cannot be controlled with medication for nearly one-third of epilepsy patients, according to the Citizens United for Research in Epilepsy organization. Having poorly controlled epilepsy appears to be the biggest risk factor for SUDEP although the underlying causes are not well understood.
Epilepsy patients who suffer generalized seizures that stem from the whole brain do not breathe during seizures and their blood oxygen levels are expected to drop, said lead study author Lisa Bateman, an assistant professor of neurology at UC Davis Medical Center.
“The somewhat surprising thing is that people who are having … more minor seizures … where the patient could just be sitting very quietly, maybe have a bit of lip smacking or a slight head turn or a bit of fumbling with their hands, would actually have such profound changes in their respiratory function as well,” she said.
Patients whose seizures begin in a specific part of the brain are candidates for surgery to control their seizures. To determine the origin of seizures, patients must be weaned off anti-epileptic medication and seizures allowed to take place under hospital supervision. Researchers monitored 56 such patients to record what happened to their brain activity, breathing, heart rate and blood oxygen levels during seizures.
A total of 304 seizures in the patients were analyzed, one third of which were accompanied by dips in blood oxygen levels to below 90 percent of normal for nearly two minutes. Notably, in 12 percent of minor cases that did not progress to generalized seizures, oxygen levels dipped below 70 percent of normal. In some patients, breathing was impaired or stopped altogether. None of the patients experienced dips in heart rate, leading the researchers to exclude cardiac problems as a cause for the drop in oxygen.
Lower dips in oxygen were often associated with longer seizures that began in the temporal lobe and then spread to other areas of the brain. The researchers posit that seizure activity in these areas may disrupt brain signaling pathways that control normal breathing.
The transient oxygen level dips may not be immediately life threatening, but the overall implication for them happening repetitively with seizures in the long run is not known, Bateman said.
In some patients, this was accompanied by a rise in blood carbon dioxide levels, which remained elevated even after their seizures ended. At a certain point, high carbon dioxide levels can cause the heart to stop functioning properly.
“Seeing that there are groups of patients whose seizures appear to have a significant impact on their respiratory function could indicate that they are at higher risk [for SUDEP] and they need to be monitored closely and intervened appropriately,” Bateman said.
Whether impaired breathing during seizures is actually a risk factor for SUDEP will require larger studies of epilepsy patients, as well as follow up studies on patients who were already monitored, she added.
“It is difficult to recommend routine oxygen monitoring in all patients with epilepsy in the hospital,” said Maromi Nei, an associate professor of neurology at Thomas Jefferson University. “However, [this study] certainly suggests that patients with epilepsy … at higher risk for seizures due to planned controlled anti-epileptic medication withdrawal should be carefully monitored, particularly for any respiratory difficulties associated with seizures.“
Besides vigilant oxygen monitoring, interventions include oxygen administration and drugs that will potentially ameliorate respiratory arrest.
ELAINE HSIA can be reached at firstname.lastname@example.org.