Application of Electrophysiologic Monitoring in Contralateral C7 Nerve Transfer Surgery.

Purpose: This study aimed to evaluate the intraoperative localization and prognostic utility of electrophysiologic monitoring for upper limb and hand muscle groups during contralateral C7 nerve transfer surgery.

Methods: In this retrospective, dual-center study, patients with spastic hemiparesis of a single upper limb who underwent contralateral C7 nerve transfer between July 2022 and November 2023 at the First Affiliated Hospital of Soochow University and Nanjing Drum Tower Hospital were included. Sensory, motor, and muscle tone changes were assessed using free electromyography, compound muscle action potentials, somatosensory evoked potentials, and transcranial electrical stimulation motor evoked potentials.

Results: Ten patients (eight males and two females; mean age: 54 ± 10.7 years) were included. Free electromyography demonstrated 100% accuracy in detecting nerve traction. Stimulation of the C7 nerve elicited 100% positive compound muscle action potential responses in the triceps brachii, extensor carpi radialis brevis, and flexor carpi ulnaris muscles. All patients exhibited somatosensory evoked potential wave amplitude reductions greater than 50%, whereas latency changes were observed in 10% of cases.

Conclusions: Real-time free electromyography and triggered stimulation enabled accurate localization of C5-C8 nerve roots. Somatosensory evoked potential and transcranial electrical stimulation motor evoked potential monitoring were predictive of postoperative sensory and motor function in the unaffected upper limb.