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Laryngeal Hemiplegia (Roaring)

By: Dr. Patricia Provost

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  • Prosthetic laryngoplasty (Tie Back Procedure) is the treatment of choice for racehorses and high-level competition horses to enable them to continue to perform competitively. This technically difficult surgical procedure, which requires that the horse be under general anesthesia, places a permanent suture to replace the function of the CAD muscle. The suture is tied tightly to result in just under maximum abduction of the affected arytenoid cartilage. In this position the horse is assured near maximum airflow when it requires it.

  • A drawback to the prosthetic laryngoplasty procedure is the permanent abduction of the arytenoid cartilage; a great benefit to the horse while it is exercising but not when it is eating. The inability to close the airway during swallowing can lead to aspiration of feed and water and chronic coughing. In a few individuals this may lead to pneumonia. Treatment in part may require removal of the permanent suture.

  • For those horses that have laryngeal hemiplegia but do not have careers that require them to compete at maximum speed and distance, research has shown that the hemiplegia does not affect their ability to breath. They receive more than enough oxygen. The noise that is made during exercise however can negatively impact the horse. Under certain horse show rules noise production is grounds for disqualification due to "unsoundness of wind". For this group of horses a prosthetic laryngoplasty will be performed in addition to either a sacculectomy (also known as ventriculectomy ) and/or a vocal cordectomy.

  • The sacculectomy does not alter the position of the affected arytenoid but does remove the tissue beneath the affected vocal cord, which acts to tighten the vocal cord when the wound heals. By removing this excess tissue and tightening the vocal cord there is less flaccid tissue to flutter in the airway as air rushes past during breathing. This will diminish the abnormal respiratory noise but will not always eliminate it unless it is combined with the prosthetic laryngoplasty. This is the procedure that is most frequently being performed on working draft horses that have laryngeal hemiplegia.

  • The vocal cordectomy involves removing the vocal cord as well as the tissue beneath it, essentially combining the sacculectomy with vocal cord removal. Some surgeons believe that this offers the best chance to eliminate the unwanted noise. It is also a procedure that is now commonly performed in adjunct to the tie-back procedure in racing horses. It does not improve the horse's ability to breathe; it only decreases the chance that there will be a respiratory noise.

  • The sacculectomy and the vocal cordectomy procedures can be performed in the standing, sedated horse or with the horse under general anesthesia, using a Laser guided by the endoscope placed through the horse's nasal passage. Alternatively the surgeries, with the horse anesthetized, can be performed with surgical instruments through a small incision made below the jaw into the throat. In either case, healing is quick and there are few complications. These procedures do not put the horse at risk for aspiration of feed or water during swallowing.

  • Nerve Muscle Pedicle Graft Transfer is a procedure that is being done on a limited basis to correct laryngeal hemiplegia. The goal of the surgery is to restore the function of the atrophied CAD muscle by transplanting a nerve to replace the failed left recurrent laryngeal nerve. The nerve that is transplanted is the 1st cervical nerve. This nerve is capable of transmitting signals to instruct the CAD muscle to contract and abduct the arytenoid during respiration. It takes 6 to 12 months for the muscle to regain its strength to be able to function normally during exercise. It is this time period that usually limits the usefulness of the procedure in horses that are in the midst of their athletic careers. It is a viable option for horses that can be given the time away from competition. There are no known complications associated with the procedure and the option exists if it fails, to have the prosthetic laryngoplasty performed. A horse that has already had a prosthetic laryngoplasty performed is not a candidate for the procedure.

    Aftercare

  • Horses that have had a prosthetic laryngoplasty performed will require antibiotics and anti-inflammatories (usually phenylbutazone) for several days following surgery. They will also require strict stall rest. It is important that they be given 4 weeks of rest to allow the muscles around the permanent suture to heal. The healed muscles will in part, along with the permanent suture, help to maintain the left arytenoid in its new abducted position. Early return to exercise jeopardizes the surgical results. Horses should have an endoscopic examination of the larynx prior to returning to exercise. Sutures will be removed at 2 weeks following surgery.

  • Initially after surgery, horses will be fed carefully to minimize the chance of aspiration of feed material. Their diet will consist of mashed grain and wet hay fed from the ground. Small volumes of food will be offered frequently at first, then gradual return to their normal diet once it is clear that they are chewing and swallowing without difficulty. For those that experience difficulty, food may be with held until the swelling and pain associated with the surgery subsides. In most instances these individuals can be returned to eating in 24 to 48 hours with no further problems.

  • Horses will also have their incision sites monitored for abnormal swelling and early signs of infection. If infection develops at the surgical site the permanent suture as a last step, may have to be removed to be able to resolve the infection.

  • Horses undergoing only a sacculectomy or vocal cordectomy will also be treated with antibiotics following surgery. The risk of infection and the consequences of infection though are much less. They will also be treated with phenylbutazone to minimize pain. Horses can be fed but again their ability to swallow is monitored. Once the pain and swelling has resolved in a few days horses are returned to their normal diet without further problems.

  • Horses undergoing only a sacculectomy or vocal cordectomy can be returned to light exercise or paddock turnout within 2 weeks and full work in 4 weeks.

  • Wound care for 3 to 4 weeks, consisting of cleaning the wound 2 to 3 times a day, will be necessary in those horses that undergo sacculectomy or vocal cordectomy through a surgical wound into the throat rather than by endoscopic Laser surgery. Care is not difficult and the surgical wound heals quickly leaving no visible scar. Some surgeons will suture the surgical wound closed at the time of the original surgery which eliminates postoperative surgical wound care.

  • Horses that have a nerve muscle pedicle graft transplant require a short course of antibiotics and phenylbutazone and two weeks of stall rest to allow the incision site to heal. Once the skin sutures are removed they can begin paddock turnout. The horse can be re-evaluated endoscopically for arytenoid function as early as 3 months but as mentioned it may take as long as 1 year for full function to return.

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