Quantitative EEG and dysautonomia in patients with temporal lobe epilepsy

The temporal lobe is considered as one of the important higher autonomic centers. It has been suggested that autonomic dysfunction could have a potential role in the pathophysiology of sudden unexpected death of epileptic patients (SUDEP). This study aimed to detect autonomic dysfunction in patients with temporal lobe epilepsy (TLE) using different electrophysiological tests and to correlate them with the SUDEP risk.

This observational case-control study included 27 TLE patients and 27 age- and gender-matched controls. Detailed history and full clinical examination were performed. Brain MRI were done. Electrophysiological studies in the form of sympathetic skin responses (SSR), heart rate variability (HRV), as well as quantitative electroencephalography (QEEG) were performed. SUDEP risk was assessed using the SUDEP-7 inventory scale.

The mean age of the recruited patients was 28.3 ± 8.26 years, with mean seizure duration of 16.59 ± 7.82 years. Epileptogenic lesions were detected in 92.6% of patients, the most common of which was the mesial sclerosis (64%). About 18.6% of the patients achieved seizure control. The patients showed a significantly reduced root mean square of successive differences (RMSSD) at deep breathing (P = 0.003), significantly higher upper limb SSR amplitudes (P = 0.01), and a significantly higher theta band absolute power (TBP) (P = 0.046/0.036). Absolute fronto-central TBP significantly correlated with the SUDEP-7 scores (r = 0.484 and 0.421; P = 0.011/0.029). ROC curve analysis for QEEG showed sensitivity of 75% and 83.3% for Fz and Cz TBP respectively.

Patients with TLE exhibit dysautonomia. Higher TBP as detected by QEEG reflects dysregulation of the higher autonomic centers, which may increase the risk of SUDEP. Thus, QEEG could serve as a sensitive, readily available biomarker for SUDEP risk screening.