LAUSR

Nerve transfer surgery (NT) constitutes an exciting option to improve upper limb functions in chronic spinal cord injury (SCI), but requires intact sublesional lower motor neuron (LMN) health. The purpose of this study was to characterize patterns of LMN abnormality in nerve-muscle groups that are the potential recipients of NT, using a standardized electrodiagnostic examination, in individuals with chronic SCI (injury duration > 2 years, injury levels C4-T1). LMN abnormality was determined using a semi-hierarchical approach, combining the amplitude compound muscle action potential (CMAP) and abnormal spontaneous activity on needle electromyography (EMG). Ten participants (46 potential recipient muscles) were included (median age=42.5 years; 6 males and 4 females; median duration from injury=15.5 years). A high frequency of LMN abnormality was observed (87%), although there was substantial variation within and between individuals. No statistically significant discordance was observed between LMN abnormality on CMAP and EMG (p=0.24), however 50% of muscles with normal CMAP demonstrated abnormal spontaneous activity. The high frequency of LMN abnormality in recipient nerve-muscle groups has implications to candidate selection for NT surgery in chronic SCI and supports the important role of the pre-operative electrodiagnostic examination. Our results further support the inclusion both CMAP and needle EMG parameters for characterization LMN health. Although the number of nerve-muscle groups with normal LMN health was small (13%), this underscores the neurophysiological potential of some patients with chronic injuries to benefit from NT surgery.