The neural bases of ictal tachycardia in temporal lobe seizures

•The neural bases of tachycardia that accompanied temporal lobe seizures remain elusive.•The study suggests that hippocampal and amygdalar ictal activity play a pivotal role in tachycardia.•The present study also suggests that ictal tachycardia is independent of ictal insular activity.

ObjectiveDue to limited information from scalp electroencephalographic (EEG) recordings, brain areas driving changes in cardiac rhythm during Temporal lobe (TL) seizures are not clearly identified. Using stereotactic EEG (SEEG) recordings, we aimed at identifying which of the brain regions involved in autonomic control trigger ictal tachycardia.MethodsThe neural activity of several mesial temporal lobe structures including amygdala, hippocampus, insula, and lateral temporal lobe recorded with SEEG were collected during 37 TL seizures in 9 patients, using indices based on High Frequency Activity (HFA). R-R intervals (RR) monitoring and time-frequency spectral analysis were performed to assess parasympathetic (High frequency power (HF)) and sympathetic (Low frequency/High frequency (LF/HF) ratio) reactivities.ResultsTachycardia was associated with a significant increase in LF/HF ratio and decrease in HF. Autonomic cardiac changes were accompanied by simultaneous SEEG signal changes with an increase in seizure-related HFA in anterior hippocampal formation and amygdala, but not in insula.ConclusionIn our sample, TL seizures are thus accompanied by an early decrease in parasympathetic control of cardiac rhythm and by an increase of sympathetic tone, concomitant to seizure activity in anterior hippocampus and amygdala.SignificanceThese results support a pivotal role of hippocampus and amygdala in tachycardia occurring during TL seizures.