Early hemodynamic differences between generalized and focal epilepsy measured by photoplethysmography

Abstract

Photoplethysmography (PPG) detects hemodynamic changes during epileptic seizures. This study aim to investigate PPG signals changes during generalized tonic‒clonic seizures (GTCSs) and focal impaired awareness seizures (FIASs). 17 GTCS and 19 FIAS episodes were recorded from 18 patients. The 30 min preictal period was divided into three 10-minute intervals. PPG features analyzed were pulse upslope (PUS), maximal compliance (Kmax), and skewness. Features across 3 preictal intervals showed significant reductions compared to the baseline: PUS (F_(3,64) = 11.870, p < 0.001), Kmax (F_(3,64) = 7.419, p < 0.001) and skewness (F_(3,64) = 2.852, p = 0.044) in the GTCS group. PUS (Kruskal-Wallis [K-W] = 22.600, p < 0.001) and Kmax (K-W = 28.110, p < 0.001) in the FIAS group. In the GTCS group, the largest difference was observed 30 min before seizure onset (PUS: p < 0.001, Cohen's d = 1.843; Kmas: p < 0.001, Cohen's d = 1.419; skewness: p = 0.043, Cohen's d = 0.808), whereas this was not the case in the FIAS group. PPG signals showed earlier changes in the GTCS group than in the FIAS group, highlighting their differences and the potential of PPG-based monitoring for early seizure detection.

Keywords: Epilepsy; Focal impaired awareness seizures; Generalized tonic‒clonic seizures; Photoplethysmography.

Fig. 1

Patient enrollment flowchart. GTCSs generalized tonic‒clonic seizures, FIASs focal impaired awareness seizures, PPG photoplethysmography, EEG electroencephalography.

Fig. 2

Violin plots (A,B) and effect size plots (C,D) of PUS, Kmax, and skewness across preictal periods. (A,C) show results from the GTCS group; (B,D) show results from the FIAS group. Violin plots display the distribution of each feature across baseline and three preictal intervals (P3, P2, P1). Internal dashed lines indicate the median (central line) and the 25th/75th percentiles (outer lines). Statistical significance: ****p < 0.0001, ***p < 0.001, **p < 0.01, *p < 0.05. Effect size plots illustrate the magnitude of differences (Cohen’s d) between baseline and each preictal period.

Fig. 3

Violin plots comparing PPG features between GTCS and FIAS groups across different preictal periods. Violin plots depict the distributions of PUS, Kmax, and skewness, respectively, across the preictal periods. The internal dashed lines represent the median (central line) and the 25th/75th percentiles (outer lines). At P3, significant differences in Kmax and skewness were observed between the GTCS and FIAS groups (Kmax: U = 94, p = 0.030; skewness: U = 89, p = 0.020). Statistical significance: *p < 0.05.