Histologic evaluation of nerve muscle pedicle graft used as a treatment for left laryngeal hemiplegia in standardbreds.

This research article investigates the effectiveness of nerve muscle pedicle (NMP) grafts in treating left laryngeal hemiplegia in horses, suggesting that a year after the surgery, the horses showed signs of reinnervation, hinting towards the procedure’s potential viability.

Research Methodology

• The study subjected six horses with induced left laryngeal hemiplegia to a nerve muscle pedicle (NMP) graft procedure. The NMP graft was created using the first cervical nerve and omohyoideus muscle.
• One of the six horses was designated the control, wherein the first cervical nerve was cut following the placement of the NMP graft.
• A year post-surgery, an endoscopic evaluation was carried out and all horses were anesthetized.
• While under anesthesia, the first cervical nerve was stimulated and the larynx observed endoscopically. Following this, the horses were euthanized and the larynx harvested for further examination.

Observations and Results

• Before anesthesia, the endoscopic appearance of the larynx in all horses was typical of laryngeal hemiplegia.
• However, following anesthesia and stimulation of the first cervical nerve, significant abduction of the left arytenoid was observed in all horses barring the control.
• The right cricoarytenoideus lateralis and CAD muscles appeared normal both grossly and histologically in all horses. In all horses, left cricoarytenoideus lateralis was atrophic, similar to the left CAD muscle of the control horse.
• The harvested left CAD muscle from the other horses demonstrated signs of reinnervation with type 1 or type 2 fiber grouping.

Conclusion and Implications

• In comparison to the control, a year after the NMP graft procedure, the principal horses with left laryngeal hemiplegia exhibited reinnervation of the left CAD muscle.
• Furthermore, they did not only show signs of reinnervation but also exhibited normal laryngeal function during exercise, according to a related study.
• The combined findings suggest that the nerve muscle pedicle (NMP) graft procedure might be a successful technique for treating left laryngeal hemiplegia in horses.