New research from Vanderbilt suggests that repeated seizures reduce brainstem connectivity, a possible contributor to unexplained neurocognitive problems in epilepsy patients.
The brainstem has been rarely studied in epilepsy because seizures typically originate in the temporal lobe or other areas of the cortex. Noting that people with temporal lobe epilepsy often lose consciousness even though the temporal lobe does not control wakefulness, Dario Englot, MD, PhD, surgical director of epilepsy at Vanderbilt University Medical Center, said he decided to focus on the region that does control wakefulness — the brainstem. He hypothesized that connectivity disruptions with the brainstem resulting from a history of seizures might play a role in diminished cognitive functions that are not related to the temporal lobe.
The research, published online May 30 in Neurology, is the first to investigate how epilepsy affects the ascending reticular activating system (ARAS) — circuitry that is responsible for regulating wakefulness — within the brainstem. Functional magnetic resonance imaging revealed that ARAS disruptions occurred, with decreases in circuitry being quantitatively associated with disease severity.
“Seizures do not start in areas deep below the surface of the brain called subcortical nuclei,” said Englot, the study’s lead author and assistant professor of Neurological Surgery, Radiology and Radiological Sciences and Biomedical Engineering. “So these areas are not often studied in epilepsy. But we think that problems develop in some deep subcortical circuits that may contribute to some of the unexplained global brain problems in temporal lobe epilepsy, including progressive neurocognitive problems and problems with arousal that can’t be explained by problems in the temporal lobe.”