Abstracts

Rationale: Epilepsy is associated with interictal and ictal autonomic dysfunction. Recently, heart rate variability (HRV) analysis has been postulated as an indicator of autonomic imbalance in epilepsy patients with risk of sudden unexpected death in epilepsy (SUDEP). However, it is unknown whether nocturnal seizures might chronically affect the HRV interictally. Therefore, we aimed to investigate nocturnal frontal lobe epilepsy (NFLE) impact on HRV during sleep. Methods: This study investigated HRV during 30-minute segments of stage 2 sleep which is of high interest in the context of autonomic function in SUDEP. HRV parameters were extracted from electrocardiography (ECG) data collected during video-electroencephalography recordings from 15 patients with NFLE and 14 patients with diurnal FLE. We strictly defined NFLE as having more than 90% of seizures during sleep. Patients who had systemic diseases and were on drugs that cause autonomic dysfunction were excluded. The exported ECG data were inspected visually to ensure that the whole sample was noise free. Time and frequency domain measures of heart rate variability were assessed using the Kubios HRV software (BiomedicalSignal Analysis Group, Department of Applied Physics University of Kuopio, Finland). Results: We did not find any statistically significant difference between nocturnal and diurnal FLE patients when testing age, sex, body mass index, disease duration, etiology, seizure frequency, seizure types and use of antiepileptic drugs. All of the patients had been seizure free for at least 24 hours before the recordings. When analysing the 30-minute recording during stage 2 sleep, NFLE group has significantly lower standard deviation of RR-intervals (P = 0.022), HRV triangular index (P = 0.009), total power (P = 0.012), low frequency power (P = 0.031) and very low frequency power (P = 0.023) then diurnal FLE group. The Poincar頣omponent SD2 (p = 0.020) was also decreased in patients with nocturnal FLE compared to diurnal FLE, whereas no significant change (p > 0.05) in SD1 was observed. Conclusions: Although this study has limitations because of the small sample size, our data suggest that patients with NFLE have suppressed HRV during sleep compared to diurnal FLE, which we postulate may be due to impaired overall activity of autonomic function. Funding: .