Quantitative evaluation of the microstructure of rapid eye movement sleep in refractory epilepsy: a preliminary study using electroencephalography and heart rate variability analysis.

Introduction: Patients with epilepsy have a disturbed sleep architecture. Polysomnographic studies have shown that patients with refractory epilepsy have decreased rapid eye movement (REM) sleep and longer REM latency than those with medically controlled epilepsy. However, little is known about the differences in the REM sleep microstructure between these patient groups.

Methods: We conducted a retrospective case-control study of 20 patients with refractory epilepsy (refractory group) and 28 patients with medically controlled epilepsy (medically controlled group). All patients completed sleep questionnaires and underwent overnight in-lab polysomnography. Five-minute electroencephalogram recordings at the C3 and C4 electrodes from each REM sleep were selected for spectral analysis, and 5-min electrocardiogram segments recorded during REM sleep were used for heart rate variability analysis. The groups' scores on the sleep questionnaires, polysomnographic sleep parameters, indices of sleep-related breathing disorders, and REM sleep electroencephalogram spectra were compared.

Results: The refractory group had decreased REM sleep (p < 0.001) and longer REM latency (p = 0.0357) than those of the medically controlled group. Moreover, electroencephalogram spectral analysis revealed that the refractory group had decreased absolute beta power (p = 0.0039) and relative beta power (p = 0.0035) as well as increased relative delta power (p = 0.0015) compared with the medically controlled group.

Conclusions: Differences in the polysomnographic macrostructure and REM sleep microstructure between the study groups suggest REM sleep dysregulation in patients with refractory epilepsy.