Neurophysiological Characterization of Motor Recovery in Acute Spinal Cord Injury

STUDY DESIGN: Prospective cohort study OBJECTIVE: This study was designed to neurophysiologically characterize motor control recovery after spinal cord injury (SCI). SETTING: University of Louisville, Louisville, Kentucky, USA. MATERIAL: Eleven acute SCI admissions and five non-injured subjects were recruited for this study. METHODS: The American Spinal Injury Association Impairment Scale (AIS) was used to categorize injury level and severity at onset. Multi-muscle surface EMG (sEMG) recording protocol of reflex and volitional motor tasks was initially performed between the day of injury and 11 days post onset (6.4 ± 3.6, mean ± SD days). Follow-up recordings were performed for up to 17 months after injury. Initial AIS distribution was: 4 AIS-A; 2 AIS-C; 5 AIS-D. Multi-muscle activation patterns were quantified from the sEMG amplitudes of selected muscles using a vector-based calculation that produces values for Magnitude and Similarity of SCI test-subject patterns to those produced by non-injured subjects. RESULTS: In SCI subjects, overall sEMG amplitudes were lower after SCI. Prime mover muscle voluntary recruitment was slower and multi-muscle patterns were disrupted by SCI. Recovery occurred in 9 of the 11 showing an increase in sEMG amplitudes, more rapid prime mover muscle recruitment rates and the progressive normalization of the multi-muscle activation patterns. The rate of increase was highly individualized, differing over time by limb and proximal or distal joint within each subject and across the SCI group. CONCLUSIONS: Recovery of voluntary motor function can be quantitatively tracked using neurophysiological methods in the domains of time and multi-muscle motor unit activation. SPONSORSHIP: NIH NINDS funded project #NS049954-01