ATLANTA — A measure of brain activity known as causal flow can help identify the cause of a seizure before it occurs, according to new research co-authored by researchers at Georgia State University and Emory University.
The study, published in the Journal of Clinical Neurophysiology, may reduce the need for invasive procedures in treating drug-resistant epilepsy.
According to the World Health Organization, approximately 50 million people worldwide have epilepsy. This neuropathy is characterized by recurrent seizures, sudden bouts of abnormal electrical activity in the brain.
“Seizures are often described as electrical storms in the brain,” said co-author Mukesh Dhamala, associate professor at the Georgia Institute of Neuroscience and Department of Physics and Astronomy. “And it can take over normal functioning. Patients can become unconscious and lose control of their behavior for seconds to minutes.”
Although some cases of epilepsy can be treated with medication, about 30% are thought to be drug-resistant. These cases require surgical intervention in the area of the brain where seizures begin, known as the seizure focus.
Neurosurgeons use an intracranial electroencephalogram (iEEG) to look for areas of abnormal activity. In this procedure, electrodes are surgically implanted into the brain during the examination. To work, the patient must have a seizure during her iEEG recording.
This approach to identifying the seizure focus is only 40-60% successful for several reasons. First, the patient must have a seizure during her iEEG recording. This can be a problem if seizures occur sporadically and without warning. Second, iEEG may miss focal regions or detect multiple areas of abnormal activity. In such cases, it is difficult, if not impossible, to visually interpret the iEEG recordings.
“We are here to assist neurosurgeons in analyzing the recorded data,” said Dhamala.
Rather than looking at the output from individual electrodes, Damala and his team began combining data from each point to get a broader picture of brain activity. These data points can be used to determine causal flow, similar to determining the location and strength of the . This is a measurement that quantifies the activity of this broader network.
Damara and his colleagues previously showed that causal flow can identify foci using high-frequency activity known to be present during seizures. In a recent study, the team was able to do the same using low-frequency activity that occurs before seizures begin. It suggests that its use may help identify seizures long before they occur.
“This method may open up entirely new possibilities for localizing seizures with a non-invasive approach,” Damala said. “That’s the idea.”
In the future, neurosurgeons may be able to identify lesions without waiting for patients to have more seizures. The team is now conducting research using functional magnetic resonance imaging to measure low-frequency activity as an alternative.
Dhamala collaborated on the paper with Sushma Ghimire, a recent Georgia State PhD graduate in physics, and Dr. Charles Epstein, a neurophysiologist and professor at Emory University.
— story Stella Meyerhoff