Distribution of Infralesional Lower Motor Neuron Injury in Traumatic Cervical Spinal Cord Injury Candidates for Upper Limb Reconstruction: A Single Center Experience

INTRODUCTION/AIMS: Patients with cervical spinal cord injury (SCI) prioritize recovery of upper extremity function. Upper extremity reconstruction can restore function in carefully selected individuals. Infralesional cord damage, observed below the neurological level of injury (NLI), may affect postoperative outcomes. We characterized the extent of infralesional lower motor neuron (LMN) injury in patients with traumatic cervical SCI. METHODS: Each patient underwent electromyography (EMG) of potential donor and recipient muscles based on preoperative clinical evaluation and specific candidacy for nerve and/or tendon transfers. The presence of infralesional pathologic insertional activity (IA), reduced motor unit potential (MUP) recruitment and/or neurogenic MUPs was assessed. The caudal-most segment with infralesional LMN injury was determined. Inclusion criteria were patients with (1) traumatic cervical SCI; (2) injury ≥ 3 months duration; (3) preoperative planning EMG for nerve and/or tendon transfers. RESULTS: Forty-eight upper extremity EMGs in 25 patients (68% male; mean age 39.5 years at injury) with traumatic cervical SCI were included. The NLI was at C7 or above in each patient, and 64% of SCIs were motor complete. Infralesional EMG abnormalities (median time from injury to EMG 466 days) were found a median of 3.0 (IQR 3.0-4.0) segments below the NLI. Three patients with an NLI as rostral as C1-C2 exhibited LMN injury seven segments below the NLI. DISCUSSION: In persons with traumatic cervical SCI, evidence of LMN injury may be observed several segments below the NLI. Defining the true extent of LMN involvement directly informs timing and selection of reconstructive procedures to maximize functional recovery.