Dysphagia resulting from unilateral rupture of the rectus capitis ventralis muscles in a horse.

Dysphagia developed in a 2-year-old Quarter Horse filly following an incident in which it fell over backward while exercising on a mechanical horse walker. Hyperextension of the neck at this time apparently caused unilateral rupture of the longus capitis (rectus capitis ventralis major) and the rectus capitis ventralis minor muscles at their insertion. An existing mycotic lesion involving the dorsomedial wall of the left guttural pouch may have weakened the area of insertion of the involved muscles. Tearing of the tendinous insertion of these muscles caused damage to the IX, X, and XI cranial nerves and left guttural pouch, with subsequent development of mild transitory epistaxis, laryngeal hemiplegia, pharyngeal paralysis, and dysphagia. Gangrenous pneumonia eventually developed because of inhalation of ingesta, and the filly was euthanatized.