Ictal and interictal respiratory changes in temporal lobe and absence epilepsy in childhood

Abstract

Autonomic dysfunctions occur during but also in between seizures. During seizures, the direct involvement of central autonomic control centers cause specific changes in heart rate and respiration. The pathophysiology of autonomic dysfunctions that are observed in the interictal period is more difficult to explain. These alterations are most likely due to changes in the epileptic network and/or to a lesser extent due to direct interictal spike activity disturbing central autonomic centers. The aim of our study is to investigate whether ictal and interictal respiratory changes do occur in temporal lobe and absence epilepsy in children. We hypothesize that the interictal autonomic changes are due to changes in the neuronal network, by studying epilepsy patients with normal interictal background EEG. Ictal and interictal single-lead ECG signals were extracted from 24h video-EEG recordings in 10 children with refractory temporal lobe seizures, in 10 children with absence seizures with occasional interictal discharges and 10 control subjects. RR interval time series were calculated and respiration parameters were derived from the ECG signal. ECG-derived respiration (EDR) signals were computed and time and frequency domain parameters were extracted to characterize the respiratory function. In the ictal registrations we observed bradypnea in 10 out of the 12 recorded seizures from the temporal lobe. In absence seizures, we observed a variable ictal effect on respiratory rate. In the analysis of the interictal data, the most remarkable finding was the higher power in the low frequency band and lower power in the high frequency band of the EDR signals in patients with absence seizures compared to control subjects, indicating a shift of respiratory rate to the lower frequencies. In conclusion we found a uniform pattern in ictal respiratory changes in temporal lobe seizures, due to direct involvement of central respiratory centers. In absence epilepsy, we found a disturbed respiratory control in between seizures. These changes were not present in the patients with temporal lobe epilepsy. The observed interictal changes in respiration in absence epilepsy are most likely due to epileptogenetic changes in the thalamocortical network, involved in absence epilepsy and could not be explained by interictal spike activity.