that is visible on clinical examination of the eye. With EMND, the
onset of clinical disease occurs only in mature animals.
Diagnosis can be made through clinical signs and symptoms and biopsy of the spinal accessory nerve to reveal oxidative damage. Blood analysis revealing vitamin E deficiency is also indicative of EMND in the adult horse.
Treatment of EMND is the supplementation of vitamin E in high daily doses.
Prognosis for individuals affected by EMND is guarded as vitamin E supplementation is shown to stop the progression of symptoms but may not be able to completely reverse long standing nerve damage.
Recurrent Laryngeal Nerve Hemiplasia
Recurrent laryngeal nerve hemiplasia is commonly called “
”.
It is caused by the idiopathic degeneration of the
nerve. This condition
may acquire or may be congenital.
The degeneration of the recurrent laryngeal nerve destroys the innervation of the cricoarytenoideus dorsalis muscle. This muscle functions to the arytenoid cartilages of the larynx and the vocal fold. Without the action of the cricoarytenoideus dorsalis muscle, the pressure generated by inspiration during exercise is sufficient to cause the vocal fold to , blocking the lumen of the airway. The air forcing past the vocal fold produces a roaring or whistling sound on . Recurrent laryngeal nerve hemiplasia is most commonly seen in large breed horses, in individuals with long necks and in males. Degeneration of the recurrent laryngeal nerve is most common as the left nerve is longer and more superficial than the right. IM injection into the left side of the neck has been reported to result in left recurrent laryngeal nerve hemiplasia. The clinical presentation of recurrent laryngeal nerve hemiplasia is usually only noted during . Most affected individuals are at rest. During exercise inspiratory stridor is audible, and the horse shows intolerance to exercise. Poor performance may also be linked to recurrent laryngeal nerve hemiplasia. Diagnosis is made through clinical signs and symptoms, and through dynamic endoscopy revealing vocal fold prolapse. Treatment is generally , where the paralyzed vocal fold is sutured to the larynx wall to prevent prolapse during exercise. This surgery is commonly called “tie-back surgery”.
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