Bilateral laryngeal paralysis associated with hepatic dysfunction and hepatic encephalopathy in six ponies and four horses

Abstract

Six ponies and four horses with a mean (sd) age of 15.9 (6.0) years developed sudden-onset bilateral laryngeal paralysis (BLP) in association with hepatic dysfunction. Nine of them had been referred for the investigation of respiratory distress, and one pony had been referred for weight loss before BLP developed. Nine of the animals had clinicopathological evidence of liver disease, and nine had histological evidence of liver disease. All of the animals had one or more of the following: hepatic encephalopathy (in eight), hyperammonaemia (in six) and endoscopic evidence of BLP (in nine). Three of the animals had signs of pituitary pars intermedia dysfunction, a diagnosis supported in two by endocrine function testing, and in two by histopathological examination. Histopathological examination of the intrinsic laryngeal musculature and recurrent laryngeal nerves of four of the horses and of the region of the nucleus ambiguus of two did not reveal any abnormalities. Three of the animals were euthanased after they had first been examined, and one improved temporarily before the condition recurred. A temporary tracheostomy was performed in six of the animals, five of which subsequently died or were euthanased; one pony recovered.

Disorders of the Face, Tongue, Esophagus, Larynx, and Ear

“…As in dogs, laryngeal paralysis in horses may be a manifestation of an underlying polyneuropathy or myopathy. 142 Postanesthetic laryngeal paralysis also has been observed. For example, laryngeal paralysis can occur secondary to hyperkalemic periodic paresis.…”

“…137,138 Isolated lesions involving structures associated along the course of the vagus and recurrent laryngeal nerve include guttural pouch disorders, pharyngeal and laryngeal disease, perineural injections of irritant drugs and trauma to the neck. 142 In such cases, laryngeal paralysis may improve with resolution of HE. In such instances, laryngeal paralysis is often observed in conjunction with other signs of generalized neuromuscular dysfunction.…”

Putative intestinal hyperammonaemia in horses: 36 cases

“…The latter has been documented in equine cases of hepatic failure and HA is frequently encountered in horses with hepatic encephalopathy (West 1996; McGorum et al . 1999; Hughes et al . 2009).…”

“…Clinical hyperammonaemia (HA) may develop due to increased production of ammonium (NH4 + ) in the intestinal tract, increased absorption of ammonia (NH3) due to increased intestinal permeability (both described as intestinal HA) or decreased hepatic clearance of NH4 + . The latter has been documented in equine cases of hepatic failure and HA is frequently encountered in horses with hepatic encephalopathy (West 1996;McGorum et al 1999;Hughes et al 2009).…”

Clinical Approach to Commonly Encountered Problems

“…255,257,259 The most common cause of non-fixed upper airway obstruction in horses is laryngeal hemiplegia, which produces inspiratory stridor during exercise. 304 A wide variety of other conditions have been associated with respiratory distress such as pneumothorax, diaphragmatic hernia, choanal atresia, nasopharyngeal cicatrix syndrome, tracheal collapse, and others. 257 Several other upper airway abnormalities have been documented, such as fourth branchial arch defect, subepiglottic cyst, aryepiglottic fold entrapment, and dorsal displacement of the soft palate.…”