Allograft Nerve Repair of a Transected Recurrent Laryngeal Nerve with Voice and Singing Recovery

INTRODUCTION

The recurrent laryngeal nerve (RLN) is a terminal branch of the vagus nerve and has motor and sensory functions that control muscles of the larynx and the movement and tension of the vocal cords. Its circuitous course may place it at risk of injury during thyroid and parathyroid surgery. Subjective voice complaints from patients are reported in 30%–87% of cases, and the incidence of RLN injury is approximately 10%, either from tumor invasion or accidental trauma.

When possible, injuries of the RLN should undergo immediate intraoperative repair. Benefits of repairing the nerve include restoring vocal cord movement, preventing atrophy of the thyroarytenoid muscle, and avoiding secondary procedures. Repair of the nerve should occur as soon as possible, as ongoing motor endplate loss and muscle denervation preclude reconstruction beyond 15-18 months, and time must also be allotted for nerve regrowth. Additionally, progressive muscle loss and endplate changes may occur shortly after injury, and continued delay or denervation can diminish the final reinnervation, based upon the available viable muscle. Unfortunately, delayed repair is associated with difficult identification of the proximal and distal nerve during re-exploration. We present the first case report of immediate RLN repair with acellular nerve allograft after laceration of the left RLN during thyroidectomy.

Case Report

The patient presented to the endocrine surgeon to discuss palpable bilateral thyroid nodules. Total thyroidectomy was recommended for the size of the left nodule, BRAF positivity, and her history of Hashimoto’s thyroiditis. Intra-operatively, baseline electromyography (EMG) measures of bilateral recurrent laryngeal nerves were obtained before dissection. The right thyroid was dissected first, then the left, and on the left, abnormal lymph nodes were present. This lymphatic tissue was removed from the left RLN, carotid, innominate artery, esophagus, and trachea from the level of the thyroid to just below the sternum. After this extensive dissection, the RLN was noticed to be transected, and stimulation from the proximal nerve produced no response in the distal (i.e., cranial) pre-laryngeal nerve segment.

An intraoperative consultation with the senior plastic surgeon (MLI) was made, and immediate repair was performed. Using 4.5x magnification loupes, the proximal and distal nerve ends were identified and dissected circumferentially. The ends of the nerve were cut back to remove the traumatized nerve until healthy bleeding fascicles were appreciated. After this procedure, a 1.8 mm gap was still present, and primary repair was not possible without undue tension. A length-matched 2-3 mm diameter acellular nerve allograft (Avance Nerve Graft, Axogen, Alachua, Fla.) was selected. This was interposed in the defect and cut to fit with no tension on each end. The proximal and distal nerve coaptations were completed with epineural repair using a 9-0 nylon. The coaptations were then protected from aberrant axonal sprouting with a 5 × 10 mm Axoguard Nerve Connector (Axogen, Alachua, Fla.). This porcine-derived nerve connector was secured in place with 9-0 nylon sutures (Figure 1).

Immediately postoperatively, the patient demonstrated a hoarse voice and an inability to sing. At three months post-operatively, she was seen in the otolaryngology clinic for laryngoscopy, which revealed left vocal cord immobility with right vocal cord compensation. At nine months follow-up, the patient reported she had a complete return to her normal speaking voice with imperceptible hoarseness and a laryngoscopy demonstrating a well-medialized left vocal cord with complete glottic closure on stroboscopy (Figure 2).

CONCLUSIONS

The RLN is critical to voice and vocal cord function, and when primary repair is not possible, an interposition acellular nerve allograft may be a safe and effective solution. In this case, voice tone had improved, and vocal cord position was more favorable after nerve repair with nerve allograft reconstruction.