Functional and histopathologic evidence of laryngeal reinnervation using the spinal accessory nerve in horses.
Authors: Campos Schweitzer Ariane, Mespoulhes-Rivière Céline, Perkins Justin D, Ducharme Norm G, Piercy Richard J, Lynch Nicola, Rossignol Fabrice
Journal: Veterinary surgery : VS
Summary
# Selective Laryngeal Reinnervation Using the Spinal Accessory Nerve in Horses with Recurrent Laryngeal Neuropathy Recurrent laryngeal neuropathy (RLN) causes progressive arytenoid abduction failure and exercise-induced upper airway obstruction in performance horses, with current surgical options largely palliative rather than curative. This prospective study evaluated whether selective reinnervation of the cricoarytenoideus dorsalis (CAD) muscle—the sole abductor of the arytenoid cartilage—using the spinal accessory nerve (SAN) could restore functional laryngeal opening in five Thoroughbred mares with experimentally induced RLN. Following left recurrent laryngeal neurectomy, horses underwent standing surgical implantation of the SAN into the CAD muscle, with functional assessment via treadmill endoscopy and muscle ultrasound at 4.5, 6, 8 and 12 months, concluding with histopathologic analysis of reinnervation success. By 12 months, four of five horses recovered arytenoid abduction to 94% of predenervation values (95% CI [90, 98]), with post-mortem examination confirming successful SAN axonal regeneration and reinnervation characterised by fibre type grouping and a shift toward oxidative type I fibres—hallmarks of functional neuromuscular recovery. For practitioners managing RLN in horses with mild to moderate CAD atrophy, this technique offers a physiologically restorative alternative to traditional permanent surgical techniques, though longer-term durability, applicability to naturally occurring disease, and optimisation of patient selection criteria warrant further investigation.
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Practical Takeaways
- •Selective laryngeal reinnervation using the spinal accessory nerve is a viable surgical option for horses with RLN and mild-to-moderate CAD muscle atrophy, with an 80% functional success rate.
- •Recovery timeline extends to 12 months post-operatively; practitioners should counsel clients on realistic expectations for gradual return of exercise tolerance.
- •This physiological approach may be considered before or alongside other RLN management strategies, particularly in horses with mild-to-moderate rather than severe laryngeal collapse.
Key Findings
- •Selective laryngeal reinnervation using the spinal accessory nerve restored arytenoid abduction at exercise in 4 of 5 horses (80% success rate) at 12 months post-operatively.
- •Mean left-to-right quotient angle ratio recovered to 94% of predenervation values with no statistically significant difference from baseline (p = 0.69).
- •Histopathologic examination confirmed successful axonal regeneration of the spinal accessory nerve and functional reinnervation of the lateral CAD muscle with increased type I fiber proportion.
- •One horse exhibited slower and incomplete recovery, demonstrating variable individual responses to the reinnervation procedure.