SUDEP, or sudden unexpected death in epilepsy, occurs when an otherwise healthy person with epilepsy dies suddenly or unexpectedly, and no clear cause of death can be found. Although SUDEP is rare, the risk is highest in people with uncontrolled generalized tonic clonic seizures, and it tends to occur at night or during sleep. Researchers are hoping to identify biomarkers for SUDEP – these are measurable characteristics that might identify who is at greatest risk. Sometimes biomarkers can be found in brain waves, which are recorded from the scalp using electroencephalography, or EEG. An EEG pattern, known as Postictal Generalized EEG Suppression (PGES), has been seen in people who have later died of SUDEP, suggesting that this brain wave pattern may be a biomarker for SUDEP.
Dr. Elizabeth Donner and colleagues wanted to study the characteristics of children who show PGES, the pattern of brain suppression activity after a seizure. They reviewed the EEG of almost 400 children whose seizures were filmed on video while their brain activity was recorded. When a seizure occurred, Dr. Donner and her team looked at the brain activity to see if they could observe this suppression afterwards.
In total, they observed 77 generalized convulsive seizures that occurred in 40 children between the ages of 1-17 years. The researchers found that suppression of brain activity was observed more often in seizures that occurred during sleep (when the risk of SUDEP is highest). Next, they looked at different characteristics to see if they might be able to predict whether or not this suppression would occur. They noticed that children who showed this suppression also showed a unique posture during their seizure, and that the part of the seizure where muscles contract was shorter.
The researchers did not notice any differences in brain wave patterns during normal sleep, which suggests that the differences are specific to seizure activity. The unique posture and the EEG suppression indicates that seizure activity may spread to the brainstem, which is a critical brain area involved in the regulation of breathing and heart rate. It is possible that the brain wave suppression is related to high levels of adenosine, a brain chemical that is involved in stopping seizures. This could disrupt heart rate or breathing patterns, possibly leading to SUDEP.
The researchers hope these results will help to identify children who may be at a higher risk for SUDEP.