Bitemporal seizure spread and its effect on autonomic dysfunction

Autonomic dysregulation is a possible pathomechanism of sudden unexpected death in epilepsy (SUDEP). Cardiac arrhythmias and autonomic symptoms are most commonly associated with seizures arising from the temporal lobes. The aim of this study was to investigate whether simultaneous seizure activity in both temporal lobes affects the autonomic nervous system differently from seizure activity in one temporal lobe as assessed by heart rate variability (HRV).

Electrocardiography (ECG) and intracranial electroencephalography (iEEG) data from 13 patients with refractory temporal lobe epilepsy who had seizures that propagated electrically from one temporal lobe to the other during video-EEG-ECG monitoring were retrospectively reviewed. The time domain, frequency domain, and nonlinear parameters of HRV were evaluated by analyzing 4-minute-long ECG epochs, sampling from baseline, preictal and postictal periods as well as epochs constituting unitemporal and bitemporal ictal activity.

Heart rate was significantly higher during bitemporal ictal activity compared with all other time points. The time domain and nonlinear parameters of HRV were significantly decreased during bitemporal activity compared with baseline, and multiple components of HRV (standard deviation of RR intervals (SDNN), coefficient of variation (CV), root mean square of successive differences (RMSSD), and standard deviation of short-term variability (SD1)) were significantly lower during bitemporal activity compared with unitemporal activity. Frequency domain analysis showed no significant differences.

This study shows that bitemporal seizure activity significantly increases heart rate and decreases HRV, indicating increased autonomic imbalance with a shift towards sympathetic predominance, and this may increase the risk of SUDEP.