van der Kruijs SJM, Vonck KEJ, Feijs LMG, Bodde NMG, Lazeron RHC, Carrette E, Boon PAJM, Backes WH, Jansen JFA, Aldenkamp AP and Cluitmans PJM
Objective: Little is known about the (peri-) ictal changes in autonomic nervous system activity of epileptic
seizures. Such information may be useful for seizure prediction paradigms and differential diagnosis between
epilepsy and psychogenic non-epileptic seizures (PNES). The current study investigated the peri-ictal time course of
heart rate variability (HRV) measures, which reflect autonomic nervous system functioning.
Methods: HRV measures were extracted from electrocardiography data collected during 1-7 days of videoelectroencephalography
monitoring of 17 patients with epilepsy and 20 patients with PNES. Heart rate (HR) and
HRV measures (standard deviation of average beat-to-beat intervals (SDANN), root mean square of successive
differences (RMSSD), high frequency (HF) power, low frequency (LF) power and very low frequency (VLF) power)
were averaged over consecutive five-minute intervals. Quantitative analyses of Poincaré plot parameters (SD1, SD2
and SD1/SD2 ratio) were also performed. In addition, differences with HRV parameters of patients with PNES were
explored.
Results: In epilepsy, no significant pre-ictal changes in HR and HRV parameters were observed. During
seizures, HR, SDANN, SD1 and SD1/SD2 ratio significantly increased while VLF power significantly decreased. In
the five-minute interval immediately following seizures, HR, SDANN and SD1 were back to pre-seizure levels, while
VLF power remained significantly decreased and SD1/SD2 ratio remained significantly increased. Significant
between-group differences were identified for several pre-ictal and ictal HRV parameters, but not for post-ictal
measurements.
Conclusion: The ictal HR and HRV changes reflect increased sympathetic system activation during epileptic
seizures. The HRV parameters of patients with epilepsy differed significantly from the peri-ictal HRV pattern of
patients with PNES, which suggested increased sympathetic system activation and decreased vagal tone shortly
before PNES and return to normal levels shortly after the episode. Implications for differential diagnosis and
treatment are discussed.