Anti-seizure medication tapering correlates with daytime delta band power reduction in the cortex

Anti-seizure medications are the primary treatment for epilepsy; yet medication tapering effects have not been investigated in a dose, region and time-dependent manner, despite their potential impact on research and clinical practice. We examined over 3000 h of intracranial EEG recordings in 32 subjects during long-term monitoring, of which 22 underwent concurrent anti-seizure medication tapering. We estimated anti-seizure medication plasma levels based on known pharmaco-kinetics of all the major anti-seizure medication types. We found an overall decrease in the power of delta band (δ) activity around the period of maximum medication withdrawal in most (80%) subjects, independent of their epilepsy type or medication combination. The degree of withdrawal correlated positively with the magnitude of δ power decrease. This dose-dependent effect was evident across all recorded cortical regions during daytime; but not in subcortical regions, or during night time. We found no evidence of a differential effect in seizure onset, spiking, or pathological brain regions. The finding of decreased δ band power during anti-seizure medication tapering agrees with previous literature. Our observed dose-dependent effect indicates that monitoring anti-seizure medication levels in cortical regions may be feasible for applications such as medication reminder systems, or closed-loop anti-seizure medication delivery systems. Anti-seizure medications are also used in other neurological and psychiatric conditions, making our findings relevant to a general neuroscience and neurology audience.