Using electrodiagnostics to define injury patterns amenable to nerve transfer surgery in tetraplegia: an illustrative case report

Introduction Spinal cord injury is a devastating condition affecting a person's independence and quality of life. Nerve transfers are increasingly used to restore critical upper extremity function. Electrodiagnostic studies guide operative planning but the implications for clinical outcomes is not well defined. This case study delineates how clinical examination and electrodiagnostics can define the varying patterns of neuronal injury to guide timing and strategy for optimal outcomes in nerve transfers. Case presentation We discuss a 20-year-old man with a C6-7 spinal cord injury (SCI). We illustrate how history, physical examination, and electrodiagnostic studies predicted patterns of upper and lower motor neuron injury, confirmed intraoperatively via direct nerve stimulation. We undertook brachialis nerve transfer to the median fascicles supplying flexor digitorum superficialis and anterior interosseous nerve (to restore digit flexion), and supinator nerve transfer to posterior interosseous nerve (to restore digit extension). Preoperative electrodiagnostics of the right upper extremity demonstrated a pure upper motor neuron injury to median innervated muscles, and mixed upper and lower motor neuron injury to radial innervated muscles. These findings were confirmed via intraoperative direct neuromuscular stimulation. The preoperative studies provided important information regarding the anatomic basis and time sensitivity of the proposed nerve transfers. At 2 years post operatively the reconstructed digit flexion and extension resulted in improved hand function and independence. Discussion Upper and lower motor neuron injuries can coexist in individuals with SCI. This example provides proof-of-concept that preoperative electrodiagnostic studies predict LMN injury, and surgery can achieve positive outcomes if completed soon after SCI.