gms | German Medical Science

Objectives/Interrogation: Contralateral C7 (CC7) nerve root has been utilized as a more prevailing procedure for treating not only disastrous peripheral nerve injuries such as brachial plexus avulsion injury (BPAI), but also spastic arm paralysis in central hemiplegic patients, with promising results reported from many centers. The premise of this procedure is that harvest of C7 nerve root would not cause permanent functional loss in the healthy extremity. However, the relative motor contribution of C7 innervation to the overall function of the upper limb remains unknown, as well as the recovery assessment of specific muscles. In the present study, cadaveric and clinical investigations were combined to delineate the motor innervation pattern of C7 nerve root and to ascertain the extent of functions that can be regained by reanimation of the C7 myotome through CC7 nerve transfer in a completely paralyzed limb suffering from BPAI.

Methods: In the anatomical study, we dissected C7 nerve root in eight embalmed adult cadavers bilaterally, and traced its branches to the muscles. In clinical study, CC7 to C7 nerve transfer was performed on eight patients with BPAI. Outcomes were evaluated by electromyography study and the muscle strength.

Results and Conclusions: Anatomically, consistent and predominantly C7-derived nerve fibers were found in the lateral pectoral, thoracodorsal and radial nerve. The average distance from the C7 nerve root to the lateral pectoral nerve entry point of the pectoralis major was 10.7 ± 1.5 cm which was the shortest. In the clinical study, for the electromyography study, compound muscle action potentials were recorded in all the muscles mentioned above. After an average follow-up of 37 months, it was found that seven out of eight patients regained M3 or higher power for shoulder adduction and elbow extension. Three patients regained M3 wrist extension. All patients were recorded the recovery of finger extension but the muscle strength was not stronger than M2.

C7 nerve root provides consistent and dominant contributions to the lateral pectoral nerve, thoracodorsal nerve and long head of triceps branch of radial nerve. For BPAI patients, after successful reinnervation of C7 nerve root, satisfying shoulder adduction and elbow extension could be anticipated, while the recoveries of wrist and finger extensions are poorer.