Electroencephalography as a Biomarker for Functional Recovery in Spinal Cord Injury Patients

Marcel Simis; Deniz Doruk Camsari; Marta Imamura; Thais Raquel Martins Filippo; Daniel Rubio De Souza; Linamara Rizzo Battistella; Felipe Fregni

doi:10.3389/fnhum.2021.548558

Electroencephalography as a Biomarker for Functional Recovery in Spinal Cord Injury Patients

Front Hum Neurosci. 2021 Apr 9:15:548558. doi: 10.3389/fnhum.2021.548558. eCollection 2021.

Authors

Marcel Simis¹, Deniz Doruk Camsari^{2

3}, Marta Imamura¹, Thais Raquel Martins Filippo⁴, Daniel Rubio De Souza¹, Linamara Rizzo Battistella¹, Felipe Fregni³

Affiliations

¹ Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil.
² Department of Psychiatry and Psychology, Mayo Clinic, Rochester, MN, United States.
³ Neuromodulation Center, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, MA, United States.
⁴ Universidade Paulista and Universidade Nove de Julho, São Paulo, Brazil.

Abstract

Background: Functional changes after spinal cord injury (SCI) are related to changes in cortical plasticity. These changes can be measured with electroencephalography (EEG) and has potential to be used as a clinical biomarker.

Method: In this longitudinal study participants underwent a total of 30 sessions of robotic-assisted gait training (RAGT) over a course of 6 weeks. The duration of each session was 30 min. Resting state EEG was recorded before and after 30-session rehabilitation therapy. To measure gait, we used the Walking Index for Spinal Cord Injury Scale, 10-Meter- Walking Test, Timed-Up-and-Go, and 6-Min-Walking Test. Balance was measured using Berg Balance Scale.

Results: Fifteen participants with incomplete SCI who had AIS C or D injuries based on American Spinal Cord Injury Association Impairment Scale classification were included in this study. Mean age was 35.7 years (range 17-51) and the mean time since injury was 17.08 (range 4-37) months. All participants showed clinical improvement with the rehabilitation program. EEG data revealed that high beta EEG activity in the central area had a negative correlation with gait (p = 0.049; β coefficient: -0.351; and adj-R ²: 0.23) and balance (p = 0.043; β coefficient: -0.158; and adj-R ²:0.24) measured at baseline, in a way that greater high beta EEG power was related to worse clinical function at baseline. Moreover, improvement in gait and balance had negative correlations with the change in alpha/theta ratio in the parietal area (Gait: p = 0.049; β coefficient: -0.351; adj-R ²: 0.23; Balance: p = 0.043; β coefficient: -0.158; and adj-R ²: 0.24).

Conclusion: In SCI, functional impairment and subsequent improvement following rehabilitation therapy with RAGT correlated with the change in cortical activity measured by EEG. Our results suggest that EEG alpha/theta ratio may be a potential surrogate marker of functional improvement during rehabilitation. Future studies are necessary to improve and validate these findings as a neurophysiological biomarker for SCI rehabilitation.

Keywords: biomarkers; electroencephalography; neuroplasticity; rehabilitation; spinal cord injury.