Doctors have long been baffled by Sudden Unexpected Death in Epilepsy (SUDEP), and a group of researchers claimed that they may have discovered the cause. A mutation in a gene involved in the regulation of calcium inside brain cells can help trigger blackouts of the brainstem, the centre that controls heartbeat and breathing, and increase the risk of a sudden unexpected death, according to Baylor College of Medicine researchers.
“SUDEP turns out to be the most common cause of premature death in people with epilepsy. It’s not accidents or suicide, it’s just this unexplained mortality,” said senior author Dr Jeffrey L. Noebels.
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He added, “Most people with epilepsy live long lives and do not seem to have an increased risk of SUDEP. But there is a subset of people at additional risk. We have been looking for genes that cause epilepsy to see if any of them might give us a clue as to who might be at risk. Specifically, we have been looking at genes that might explain what appears to be a collapse of the cardiac and respiratory system after a seizure.”
Noebels and his colleagues studied genes involved in a heartbeat in their years-long quest to understand the cellular and genetic mechanisms that may trigger SUDEP. Some of these genes have been linked to sudden unexpected cardiac death in the past.
“We wondered whether some of those same genes could also cause seizures if they were expressed in the brain, and, if so, whether those genes would also place people with epilepsy at risk, not only for having epilepsy, but an abnormal heartbeat and risk of death,” said Noebels.
“In our first experiments we found several genes that actually filled that description: they are expressed in the brain and the heart, and mutations of those genes cause an abnormal heartbeat and epilepsy in mouse models.”
The researchers discovered that these same genes are linked to a condition known as spreading depolarization, which is a slow-moving, temporary electrical blackout of a brain region. During a blackout, the brain cells in that area stop functioning until the blackout is over.
Noebels and colleagues looked at another gene, RyR2, which is expressed in the heart and has been linked to heart disease. They discovered that RyR2, which is also expressed in the brain, causes epilepsy in mice and causes an electrical surge, which increases the likelihood of a fatal blackout.
The discovery of how the ‘leaky’ RyR2 increases the risk of SUDEP, according to Noebels and colleagues, is a step toward a future in which neurologists could sit down with a patient and their family and discuss the possibility of providing an accurate prediction of SUDEP risks and effective interventions.
The findings of the study were published in the Proceedings of the National Academy of Sciences.
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