VN June 2021

Vetnuus | Junie 2021 8 University of Pretoria veterinary specialist performs what is believed to be SA’s first neuroprosthesis on a horse The patient, a two-year-old racing filly, suffered from respiratory noise and exercise intolerance secondary to laryngeal hemiplegia, which is one-sided paralysis of the larynx. Dr Juan Muñoz, senior Lecturer in the Department of Companion Animal Clinical Studies at the Faculty of Veterinary Science and Dr. Felipe Corrêa, equine surgery resident, used a new technique to treat the horse. The larynx consists of a group of cartilages that allow air to pass into the trachea. Horses with laryngeal hemiplegia present a progressive paralysis of one of these cartilages, normally the left arytenoid, due to lack of innervation, causing atrophy to the cricoarytenoid dorsalis muscle that moves this cartilage. The paralysis prevents the cartilage from opening the throat during inspiration. This leads to decreased airflow into the lungs due to obstruction from the paralysed cartilage, resulting in respiratory noise and exercise intolerance. Horses with this disease are called“roarers”because they make a characteristic respiratory noise that sounds like“roaring”when exercised. “This filly was not able to participate in horse racing due to the presence of a laryngeal hemiplegia in an early stage of the disease. In more severe cases or when the pathology is bilateral, patients are unable to exercise or can even die because of asphyxia,”explained Dr Muñoz. The patient was brought to the Onderstepoort Veterinary Academic Hospital as it had a respiratory noise. An overground dynamic endoscopy was performed that revealed a grade 3/4 left side laryngeal hemiplegia. Overground dynamic endoscopy is the gold standard imaging technique to diagnose airway problems that occur when a horse is exercising, as some conditions will only be seen with the horse moving at speed. This procedure is performed by inserting an endoscope into the horse’s nasal cavity to visualise the pharynx and larynx area. The horse is then exercised and the data is recorded in a computer located underneath the saddle. Playing the video back in slowmotion allows visualisation and assessment of the functioning of the pharynx and larynx. Classically, horses with laryngeal hemiplegia are treated by laryngoplasty and ventriculocordectomy under general anaesthesia. With the laryngoplasty, the paralysed cartilage is“tied back”into an open position with a suture through an incision in the throat latch area. Article