Efficacy of Surgery for Laryngeal Hemiplegia

CHAPTER 54 Efficacy of Surgery for Laryngeal Hemiplegia



Jennifer A. Brown


In the late part of the nineteenth century, horses affected with roaring caused by laryngeal hemiplegia were considered hopeless cases. At that time, permanent tracheotomy was the only viable surgical option. A veterinary surgeon from Hanover, Germany, was exploring the value of left arytenoidectomy and ventricle stripping, but these procedures were not considered successful because of a high associated fatality rate.


In the early 1900s, Sir Frederick Hobday refined the technique for ventriculectomy through the cricothyroid membrane using a sacculectomy burr. In an article titled “The Surgical Treatment of Roaring in Horses” (1935), he described a procedure that varied little from the technique used at present, and he reported an 85% success rate in hunters and a 95% success rate in carriage and cart horses. In that article, it was also pointed out that this procedure would be beneficial in war horses because it eliminated the shrill whinny that could give away a troop’s position to the enemy.


Substantial advances in the treatment of roaring were not made again until the 1960s and 1970s, when the horse’s larynx could be evaluated endoscopically. In 1970 Marks and colleagues described prosthetic laryngoplasty as a new surgical treatment for the disease. Prosthetic laryngoplasty, with and without vocal cord and ventricular surgeries, became the gold standard treatment for all horses affected by laryngeal paralysis and has been the subject of extensive research into the twenty-first century.


Two additional procedures have been described, evaluated, and used to manage roaring in horses: arytenoidectomy (partial and sub-total) and laryngeal reinnervation. These two procedures, along with prosthetic laryngoplasty, and the various combinations of vocal cord and ventricle surgery, complete the current arsenal available to veterinarians for treatment of laryngeal hemiplegia in the horse.



LARYNGEAL REINNERVATION


Also known as the nerve-muscle pedicle graft, this surgical procedure was developed to restore function of the cricoarytenoideus dorsalis muscle by transplanting muscle pedicles from adjacent healthy skeletal muscle.


With this procedure, the omohyoideus muscle is used as the donor muscle. This muscle, an accessory muscle of respiration, is innervated by the first and second cervical nerves. The first cervical nerve is carefully dissected free of surrounding connective tissue where it crosses the lateral aspect of the larynx to its insertion on the omohyoideus muscle, at which point it separates into two or three branches. Muscle pedicles are harvested in 3-mm–square sections with fine scissors where the nerve branches insert into the muscle, and with nerves intact, these pedicles act as the graft for reinnervation. Up to five sections can be used for transplantation into the cricoarytenoideus dorsalis muscle. The grafts are inserted into pockets made in the cricoarytenoideus dorsalis and sutured into place.



Complications


Reported complications include seroma formation at the surgery site, development of sialocele from damage to the parotid salivary gland during dissection of the nerve, and failure of the surgery. Some of the major complications associated with other laryngeal surgeries, such as arytenoidectomy and laryngoplasty, have not been recognized.



Efficacy


In experimental horses, this procedure improved upper airway function as measured by flow-volume loops in exercising Standardbreds by 6 months after surgery. Histologic evaluation revealed reinnervation of the cricoarytenoideus dorsalis muscle to progress over time. In clinical cases, approximately 65% of horses that undergo the surgery will race successfully. In a study by Fulton and colleagues, it was reported that 58% and 53% of 121 horses that had raced before surgery had an increase in performance score and increased earnings, respectively.

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May 28, 2016 | Posted by in EQUINE MEDICINE | Comments Off on Efficacy of Surgery for Laryngeal Hemiplegia

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