Relationship Between Brain Activity and Impaired Consciousness in Frontal Lobe Seizures

BACKGROUND AND OBJECTIVES: Impaired consciousness in epilepsy negatively affects quality of life. Previous work has focused on temporal lobe seizures, where cortical slow waves are associated with depressed subcortical arousal and impaired consciousness. However, it is unknown whether frontal lobe seizures also show cortical slow waves or a different activity pattern with impaired consciousness. METHODS: Intracranial EEG (icEEG) recordings from patients at 3 centers were retrospectively assessed to identify seizures originating in the frontal lobe. Seizures were classified as focal preserved consciousness (FPC), focal impaired consciousness (FIC), or focal to bilateral tonic-clonic (FBTC) based on video review. Changes in icEEG power from preictal baseline were calculated in different cortical regions and across frequency ranges in these 3 seizure categories. RESULTS: < 0.001, 95% CI 330.1-781.9 and 375.3-818.2, respectively). DISCUSSION: The widespread power increases across frequencies in frontal lobe FIC seizures contrast with those in focal temporal lobe epilepsy, where impaired consciousness is associated with cortical slow waves. These findings suggest that different focal seizure types produce impaired consciousness by affecting widespread cortical regions but through different physiologic mechanisms. Insights gained by studying the physiology of impaired consciousness may be the first step toward developing novel treatments to prevent this significant negative consequence of epilepsy and improve quality of life.