Long-Term Outcomes of Spinal Accessory Nerve to Musculocutaneous Nerve Transfer in Brachial Plexus Birth Injuries.

PURPOSE: Brachial plexus birth injuries (BPBI) can be life-changing for both the patient and family. While most resolve spontaneously, surgical intervention is indicated for those who fail to improve. This can be performed via nerve grafting or nerve transfer. The spinal accessory nerve is a commonly used extraplexal donor in brachial plexus surgery. In cases of BPBI, it can be transferred to the musculocutaneous nerve to restore elbow flexion. While there are short-term reports in BPBI, few, if any, long-term outcome data are available.

METHODS: A retrospective review of patients who underwent spinal accessory nerve to musculocutaneous nerve transfer for a BPBI was undertaken. Patients were excluded if they had <2 years of follow-up or could not follow instructions for manual motor testing at the most recent follow-up. Patient demographics, including age at time of surgery, were recorded. The primary outcome was final elbow flexion using a modified British Medical Research Council (mBMRC) grade. Secondary outcomes included time to varying Active Movement Scale scores, final trapezius mBMRC grade, Mallet grade, Patient-Reported Outcomes Measurement Information System (PROMIS) pain interference, PROMIS physical function, and any secondary surgeries.

RESULTS: Six patients were included. Surgery was performed at an average of 3 months of age. All patients sustained global plexus injuries. Average clinical follow-up was 12 years. Patients first showed signs of muscle contraction (Active Movement Scale grade 1) at an average of 6 months after surgery. All patients reached mBMRC grade 4 or greater elbow flexion strength by final follow-up. All patients had mBMRC grade 5 upper trapezius strength at final follow-up. Average Mallet grade for global shoulder abduction was 3.2 and global shoulder external rotation 4.2. Both PROMIS pain interference and physical function scores were within normal limits at final follow-up, with averages of 48.3 and 49.0, respectively. Four of 6 patients had secondary surgery; however, none had additional surgery to address elbow flexion.

CONCLUSIONS: Spinal accessory nerve to musculocutaneous nerve transfer effectively restores elbow flexion strength in patients with BPBI who need elbow flexion. Outcomes remained durable with over a decade of follow-up, without compromising upper trapezius strength.

TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.