Interictal change in cardiac autonomic function associated with EEG abnormalities and clinical symptoms : A longitudinal study following acute deterioration in two patients with temporal lobe epilepsy

The purpose of the present study was to investigate the ictal and interictal changes in cardiac autonomic function (CAF), and the relationship between the interictal change in CAF to the electroencephalogram (EEG) and clinical findings. In two patients with temporal lobe epilepsy (TLE) showing acute deterioration, a quantitative evaluation of their interictal CAF based on heart rate variability and their EEG using spectral analysis was conducted, and the findings compared with repeated clinical evaluations during the recovery period. The ictal heart rate changes and their temporal relationship to ictal discharge were investigated using simultaneous EEG/electrocardiogram (ECG) monitoring in one of the patients. Interictal parasympathetic function was decreased during the period of acute deterioration, but was increased in association with improvements in the EEG and clinical findings. In contrast, the sympathetic function showed no specific changes. The ictal discharges were preceded by a brief bradycardia, with a long delay of up to 40 s. The results demonstrated that this decrease in parasympathetic function was closely related to the interictal changes in central nervous system function. On the other hand, the ictal discharges in one of the patients were thought to have caused a transient elevation of parasympathetic function. It is strongly suggested that patients with TLE have interictal as well as ictal changes in CAF that are mediated mainly through the parasympathetic nervous system.