Spinal Cord Stimulation for Prolonged Disorders of Consciousness: A Study on Scalp Electroencephalography

Patients with disorders of consciousness (DOC) undergoing spinal cord stimulation (SCS) for arousal treatment require an assessment of their conscious state before and after the procedure. This is typically evaluated using behavioral scales (CRS-R), but this method can be influenced by the subjectivity of the physician. Event-related potentials (ERP) and EEG power spectrum are associated with the recovery of consciousness. This study aims to explore the electrophysiological and behavioral evidence of consciousness recovery in DOC patients after spinal cord stimulation (SCS) and to investigate the role of scalp EEG as a guide for preoperative assessment related to the surgery.

For the 27 recruited patients, the CRS-R scale assessment and ERP P300 evaluation were completed before the surgery. At 3 months post-surgery, all 27 patients underwent the same assessments as preoperatively, and at 6 months post-surgery, the same evaluations were repeated for the 15 patients who could still be followed up. Between May 2023 and November 2023, resting-state EEG was collected from 13 patients using a 19-channel setup, with additional resting-state EEG recordings taken at 3 months and 6 months after the surgery. The EEG data were processed using EEGLAB to obtain P300-related metrics and EEG power spectrum. Changes in the CRS-R scale, ERP, and EEG power spectrum before and after the surgery were compared.

The Behavioral Scale (CRS-R) showed significant improvement at 3 months and 6 months post-surgery compared to preoperative assessments, with statistical significance (p < 0.001). The resting-state EEG power in the 5-9 Hz frequency band demonstrated statistically significant improvements at the P3 and O1 electrodes; however, this statistical result do not survive FDR correction. In the 9-13 Hz and 20-35 Hz frequency bands, the power spectrum showed statistically significant improvements across most electrodes of the brain, and these results survive FDR correction (p < 0.05). The mean amplitude, peak, and latency of P300 at the Pz electrode showed significant improvements at 3 months and 6 months post-surgery compared to preoperative values, with statistical significance (p < 0.05).

Our study shows that SCS can effectively improve the consciousness states of patients with DOC. After surgery, there were positive changes in the EEG power spectrum of the patients, transitioning from type "B" to better types "C" and "D." The average amplitude, peak, and latency of P300 also demonstrated significant improvements postoperatively. We believe that the "ABCD" model and ERP assessment applied during the preoperative evaluation can effectively enhance the success rate of SCS surgery in promoting awakening.