Nerve fascicle transfer using a part of the C-7 nerve for spinal accessory nerve injury

Abstract

OBJECTIVESpinal accessory nerve (SAN) injury results in a series of shoulder dysfunctions and continuous pain. However, current treatments are limited by the lack of donor nerves as well as by undesirable nerve regeneration. Here, the authors report a modified nerve transfer technique in which they employ a nerve fascicle from the posterior division (PD) of the ipsilateral C-7 nerve to repair SAN injury. The technique, first performed in cadavers, was then undertaken in 2 patients.METHODSSix fresh cadavers (12 sides of the SAN and ipsilateral C-7) were studied to observe the anatomical relationship between the SAN and C-7 nerve. The length from artificial bifurcation of the middle trunk to the point of the posterior cord formation in the PD (namely, donor nerve fascicle) and the linear distance from the cut end of the donor fascicle to both sites of the jugular foramen and medial border of the trapezius muscle (d-SCM and d-Traps, respectively) were measured. Meanwhile, an optimal route for nerve fascicle transfer (NFT) was designed. The authors then performed successful NFT operations in 2 patients, one with an injury at the proximal SAN and another with an injury at the distal SAN.RESULTSThe mean lengths of the cadaver donor nerve fascicle, d-SCM, and d-Traps were 4.2, 5.2, and 2.5 cm, respectively. In one patient who underwent proximal SAN excision necessitated by a partial thyroidectomy, early signs of reinnervation were seen on electrophysiological testing at 6 months after surgery, and an impaired left trapezius muscle, which was completely atrophic preoperatively, had visible signs of improvement (from grade M0 to grade M3 strength). In the other patient in whom a distal SAN injury was the result of a neck cyst resection, reinnervation and complex repetitive discharges were seen 1 year after surgery. Additionally, the patient’s denervated trapezius muscle was completely resolved (from grade M2 to grade M4 strength), and her shoulder pain had disappeared by the time of final assessment.CONCLUSIONSNFT using a partial C-7 nerve is a feasible and efficacious method to repair an injured SAN, which provides an alternative option for treatment of SAN injury.