Modified first or second cervical nerve transplantation technique for the treatment of recurrent laryngeal neuropathy in horses

Abstract

Background: In horses, the only established method for reinnervation of the larynx is the nerve-muscle pedicle implantation, whereas in human medicine, direct nerve implantation is a standard surgical technique for selective laryngeal reinnervation in human patients suffering from bilateral vocal fold paralysis. Objectives: (1) To describe a modified first or second cervical nerve transplantation technique for the treatment of recurrent laryngeal neuropathy (RLN) in horses and (2) evaluate the outcomes of reinnervation using direct nerve needle-stimulation of the first cervical nerve and exercising endoscopy before and after surgery. Study design: Case series. Methods: Nerve transplantation surgery, in which the first or second cervical nerve is tunnelled through the atrophied left cricoarytenoideus dorsalis muscle, was performed in combination with ipsilateral laser ventriculocordectomy. Ultrasound-guided stimulation of the first cervical nerve at the level of the alar foramen was used to confirm successful reinnervation post-operatively. Exercising endoscopy was performed before and after surgery. The exercising RLN grade of the left arytenoid was blindly determined at the highest stride frequency for each examination. Results: Surgery was performed in 17 client-owned animals with RLN. Reinnervation was confirmed by nerve stimulation and subsequent arytenoid abduction observed in 11 out of 12 cases between 4 and 12 months post-operatively. Fourteen horses had exercising endoscopy before and after surgery. Nine horses had an improved exercising RLN grade, four horses had the same exercising grade and one horse had a worse exercising grade after surgery. Main limitations: A sham-operated control group was not included and follow-up beyond 12 months and objective performance data were not obtained. Conclusions: The modified first or second cervical nerve transplantation technique, using tunnelling and direct implantation of the donor nerve into the cricoarytenoideus dorsalis muscle, resulted in reinnervation in 11 out of 12 cases and improved exercising grade in 9 out of 14 horses within 12 months after surgery.