Estimated EEG functional connectivity and aperiodic component induced by vagal nerve stimulation in patients with drug-resistant epilepsy

Roberta Coa; Simone Maurizio La Cava; Giulia Baldazzi; Lorenzo Polizzi; Giovanni Pinna; Carlo Conti; Giovanni Defazio; Danilo Pani; Monica Puligheddu

doi:10.3389/fneur.2022.1030118

Estimated EEG functional connectivity and aperiodic component induced by vagal nerve stimulation in patients with drug-resistant epilepsy

Front Neurol. 2022 Nov 23:13:1030118. doi: 10.3389/fneur.2022.1030118. eCollection 2022.

Authors

Roberta Coa¹, Simone Maurizio La Cava², Giulia Baldazzi^{2

3}, Lorenzo Polizzi⁴, Giovanni Pinna⁵, Carlo Conti⁵, Giovanni Defazio^{4

6}, Danilo Pani², Monica Puligheddu^{4

6}

Affiliations

¹ Neuroscience Ph.D. Program, Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy.
² Department of Electrical and Electronic Engineering, University of Cagliari, Cagliari, Italy.
³ Department of Informatics, Bioengineering, Robotics and Systems Engineering, University of Genova, Genova, Italy.
⁴ Regional Center for the Diagnosis and Treatment of Adult Epilepsy, Neurology Unit, AOU Cagliari, Cagliari, Italy.
⁵ SC Neurosurgery, Neuroscience and Rehabilitation Department, San Michele Hospital, ARNAS G. Brotzu, Cagliari, Italy.
⁶ Department of Medical Sciences and Public Health, University of Cagliari, Cagliari, Italy.

Abstract

Background: Vagal nerve stimulation (VNS) improves seizure frequency and quality of life in patients with drug-resistant epilepsy (DRE), although the exact mechanism is not fully understood. Previous studies have evaluated the effect of VNS on functional connectivity using the phase lag index (PLI), but none has analyzed its effect on EEG aperiodic parameters (offset and exponent), which are highly conserved and related to physiological functions.

Objective: This study aimed to evaluate the effect of VNS on PLI and aperiodic parameters and infer whether these changes correlate with clinical responses in subjects with DRE.

Materials and methods: PLI, exponent, and offset were derived for each epoch (and each frequency band for PLI), on scalp-derived 64-channel EEG traces of 10 subjects with DRE, recorded before and 1 year after VNS. PLI, exponent, and offset were compared before and after VNS for each patient on a global basis, individual scalp regions, and channels and separately in responders and non-responders. A correlation analysis was performed between global changes in PLI and aperiodic parameters and clinical response.

Results: PLI (global and regional) decreased after VNS for gamma and delta bands and increased for an alpha band in responders, but it was not modified in non-responders. Aperiodic parameters after VNS showed an opposite trend in responders vs. non-responders: both were reduced in responders after VNS, but they were increased in non-responders. Changes in aperiodic parameters correlated with the clinical response.

Conclusion: This study explored the action of VNS therapy from a new perspective and identified EEG aperiodic parameters as a new and promising method to analyze the efficacy of neuromodulation.

Keywords: EEG; aperiodic component; drug-resistant epilepsy (DRE); functional connectivity (Fc); vagus nerve stimulation (VNS).