Feline Dysautonomia

Affected cats initially are anorectic and often have upper respiratory signs or transient diarrhea. The onset of more definite signs varies from peracute to chronic. Failure of the autonomic system of the GI and urinary tracts can cause esophageal distention and/or dysfunction, gastric and bowel distention and hypomotility, and urinary bladder distention. Other common signs include dilated, nonresponsive pupils, ptosis, and third eyelid protrusion; a dry rhinarium; and reduced lacrimal secretion. In addition, dry oral mucous membranes, prolapse of the nictitating membrane, bradycardia, and urinary or fecal incontinence may be seen. These signs reflect both sympathetic and parasympathetic dysfunction, and there is a wide range in the severity of presenting signs. A dilated anus is sometimes noted, but the underlying somatic lesion is undetermined. Clinical pathology findings are nonspecific.

Definitive diagnosis depends on histopathologic examination of autonomic ganglia. Clinical confirmation may be aided by contrast radiography (including fluoroscopy) of the esophagus and by reduced lacrimal secretion (<5 mm/min when measured by the Schirmer tear test). Pilocarpine (0.1%) applied to the cornea causes profound miosis within 10–15 min due to denervation hypersensitivity but has no effect on a healthy cat. Dilute (0.5%) phenylephrine reverses the ptosis and protruding third eyelid. Although feline leukemia virus (FeLV, see Feline Leukemia Virus and Related Diseases) infection can cause both anisocoria and urinary incontinence, cats with dysautonomia usually show other clinical signs and are FeLV-negative.

The main aim of therapy is first to rehydrate the cat and then to maintain adequate fluid balance. Total parenteral nutrition is useful initially but later can be replaced by gastrostomy or nasogastric tube feeding when regurgitation resolves. Maintaining an upright posture after oral intake is important, because the main complication of this condition is inhalation pneumonia. Thrice daily evacuation of the bladder, provision of warmth, use of artificial tears and steam inhalation, and assistance with grooming are all important nursing considerations. Liquid paraffin PO is helpful for constipation but increases the risk of aspiration. Other parasympathomimetics, such as bethanechol (1–2.5 mg, PO, bid-tid), may be of use; however, their effect is crude, and overdosage requires treatment with atropine. Metoclopramide (0.1 mg/kg, IV, or 0.3 mg/kg, SC, tid) may improve gastric emptying.

A small proportion of cats have recovered, and others are able to cope with residual autonomic deficits. Such improvements often require up to 1 yr. In general, the prognosis is poor for severely affected cats.