New Epilepsy Research at Baylor College of Medicine Provides Insight on Absence Seizures
To an observer, an epileptic seizure that involves uncontrollable jerking of the body can be frightening to witness. But there are other types of seizures associated with the neurological disorder that are quite subtle and easy to overlook.
Those subtle seizures, often referred to as absence seizures because the person experiencing it has a moment of “absence”, can be almost impossible to detect by a casual observer. The absence seizures are brief and often look like the epileptic is simply daydreaming, or lost in thought. Even those who experience the absence seizures may not be aware that it is occurring. One sign that might alert an observer is if the individual’s eyes blink a lot or roll up. According to the U.S. Centers for Disease Control, approximately 3.4 million people in the United States suffer from epilepsy. Absence epilepsy is the most common type of seizure disorder in children and is the focus of a new neurology study at Baylor College of Medicine and published in the journal Nature Communications.
Jochen Meyer, a neuroscience instructor at the college, said that absence seizures typically stop around the time a child enters puberty in about 80 percent of the cases. The other 20 percent will continue to have seizures, he said. Meyer added that even in the cases where the absence seizures stop, absence epilepsy is still a disabling disorder because the seizures “cause children to be momentarily absent during periods of their formative years.”
Atul Maheshwari, an assistant professor of neurology and neuroscience at Baylor and a co-author of the Baylor study, said it’s important to have a better understanding of how the brain is affected during an absence seizure. Maheshwari said that many of the children who experience absence epilepsy also show signs of attention deficit disorder. That can persist in about 40 percent of patients despite being treated with medication and even after the seizures stop, he said.
A better understanding of the brain is what the Baylor research team has achieved in this study. A new technology called 2-photon microscopy allowed the researchers to “visualize the firing activity of many individual neurons simultaneously in the brains of awake mice,” a Baylor release said. The new information was combined with observations made from electroencephalograms that measured the electrical patterns of the same area of the brain. The researchers said the results were completely unexpected. For years, the Baylor team said it’s been known that people having an absence seizure present with an electroencephalogram shows a “spike and wave” pattern of electrical activity during the seizure. Neurology professor Jeffrey Noebels, a member of the research team, said they predicted that pattern would be a rhythmical activity. Instead, they saw “an uncoordinated firing activity,” he was a surprise.
It was always thought that during the ‘spike’ cells would fire, and during the ‘wave’ they would be quiet. That repeated pattern of spike-and-wave is the signature of this kind of epilepsy, so we assumed that it was based on the behavior of the cells that were generating the brain waves. But in fact, we found that there appears to be no uniform connection between the cell behavior and the brain waves,” Noebel said in a statement.
With that new understanding of how the brain works during these seizures, the researchers said the medical community can now begin to “look for ways to treat the underlying causes of the seizures at the cellular level.”
Currently, there are several drugs on the market that are used to treat absence seizures. Among the approved treatments for absence, seizures are ethosuximide, valporic acid and lamotrigine. Earlier this year the FDA issued a warning about lamotrigine, sold under the brand name Lamictal, regarding a rare drug reaction that “excessively activates the body’s infection-fighting immune system.” With the Baylor result, it’s possible that a new treatment will be available for those absence seizure patients.