Correlation of bilateral M1 hand area excitability and overall functional recovery after spinal cord injury: protocol for a prospective cohort study.

BACKGROUND: After spinal cord injury (SCI), a large number of survivors suffer from severe motor dysfunction (MD). Although the injury site is in the spinal cord, excitability significantly decreases in the primary motor cortex (M1), especially in the lower extremity (LE) area. Unfortunately, M1 LE area-targeted repetitive transcranial magnetic stimulation (rTMS) has not achieved significant motor improvement in individuals with SCI. A recent study reported that the M1 hand area in individuals with SCl contains a compositional code (the movement-coding component of neural activity) that links matching movements from the upper extremities (UE) and the LE. However, the correlation between bilateral M1 hand area excitability and overall functional recovery is unknown. OBJECTIVE: To clarify the changes in the excitability of the bilateral M1 hand area after SCI and its correlation with motor recovery, we aim to specify the therapeutic parameters of rTMS for SCI motor rehabilitation. METHODS: This study is a 12-month prospective cohort study. The neurophysiological and overall functional status of the participants will be assessed. The primary outcomes included single-pulse and paired-pulse TMS. The second outcome included functional near-infrared spectroscopy (fNIRS) measurements. Overall functional status included total motor score, modified Ashworth scale score, ASIA Impairment Scale grade, spinal cord independence measure and modified Barthel index. The data will be recorded for individuals with SCI at disease durations of 1 month, 2 months, 4 months, 6 months and 12 months. The matched healthy controls will be measured during the same period of time after recruitment. DISCUSSION: The present study is the first to analyze the role of bilateral M1 hand area excitability changes in the evaluation and prediction of overall functional recovery (including motor function and activities of daily living) after SCI, which will further expand the traditional theory of the predominant role of M1, optimize the current rTMS treatment, and explore the brain-computer interface design for individuals with SCI. TRIAL REGISTRATION NUMBER: ChiCTR2300068831.

Primary motor hand area corticospinal excitability indicates overall functional recovery after spinal cord injury.

Background: After spinal cord injury (SCI), the excitability of the primary motor cortex (M1) lower extremity area decreases or disappears. A recent study reported that the M1 hand area of the SCI patient encodes the activity information of both the upper and lower extremities. However, the characteristics of the M1 hand area corticospinal excitability (CSE) changes after SCI and its correlation with extremities motor function are still unknown. Methods: A retrospective study was conducted on the data of 347 SCI patients and 80 healthy controls on motor evoked potentials (MEP, reflection of CSE), extremity motor function, and activities of daily living (ADL) ability. Correlation analysis and multiple linear regression analysis were conducted to analyze the relationship between the degree of MEP hemispheric conversion and extremity motor function/ADL ability. Results: The CSE of the dominant hemisphere M1 hand area decreased in SCI patients. In 0-6 m, AIS A grade, or non-cervical injury SCI patients, the degree of M1 hand area MEP hemispheric conversion was positively correlated with total motor score, lower extremity motor score (LEMS), and ADL ability. Multiple linear regression analysis further confirmed the contribution of MEP hemispheric conversion degree in ADL changes as an independent factor. Conclusion: The closer the degree of M1 hand area MEP hemispheric conversion is to that of healthy controls, the better the extremity motor function/ADL ability patients achieve. Based on the law of this phenomenon, targeted intervention to regulate the excitability of bilateral M1 hand areas might be a novel strategy for SCI overall functional recovery.

Analgesia-enhancing effects of repetitive transcranial magnetic stimulation on neuropathic pain after spinal cord injury:An fNIRS study.

BACKGROUND: Repetitive transcranial magnetic stimulation (rTMS) is a promising treatment for chronic intractable neuropathic pain in patients with spinal cord injury (SCI). However, the analgesia-enhancing effects of rTMS on conventional interventions (e.g., medications), and the underlying mechanisms remain poorly understood. OBJECTIVE: To investigate the enhancement of analgesia and change of cortex activation by rTMS treatment on neuropathic pain following SCI. METHODS: A double-blind, sham-controlled, clinical trial was performed. Twenty-one patients with neuropathic pain after SCI were randomized (2:1) to receive a session of rTMS (10 Hz, a total of 1200 pulses at an intensity of 80% resting motor threshold) or sham treatment over the left primary motor cortex (M1) corresponding to the hand area daily for six weeks with a one-day interval per week. At T0 (before rTMS treatment), T1 (after the first session rTMS), T2 (after one week), T3 (after two weeks), T4 (after four weeks) and T5 (after six weeks), activations in the bilateral M1, primary somatosensory cortex (S1), premotor cortex (PMC) and prefrontal cortex (PFC) during the handgrip task were measured using functional near-infrared spectroscopy (fNIRS). In addition, the numerical rating scale (NRS) was used to assess pain. RESULTS: The pain intensity or activation in PFC, PMC, M1 or S1 was not remarkably changed at T1. Along with the time, the pain intensity gradually decreased in both the rTMS and sham groups. The real rTMS, compared with the sham, showed more pain relief from two weeks (T3) to six weeks (T5), and the activations of the motor-related areas M1 and PMC were remarkably suppressed. CONCLUSIONS: The findings of this preliminary study with a small patient sample suggest that the analgesia-enhancing effects of high-frequency rTMS might be related with the amelioration of M1 and PMC hypersensitivity, shedding light upon the clinical treatment of SCI-related neuropathic pain.