Canine dysautonomia is a degenerative polyneuropathy characterized by neuronal degeneration within the autonomic, somatic, central, peripheral and/or enteric nervous system causing multisystemic effects similar, if not identical, to the dysautonomia in cats, horses, rabbits, and hares. Canine dysautonomia was first described in England in 1983. Although individual cases have been reported in Scotland, Norway, Belgium, Germany and Greece, canine dysautonomia is less commonly reported in Europe compared with the high numbers reported in the USA, primarily in the midwest. In the USA risk factors were reported to include a rural habitat and spending more than 50% of the time free outdoors.
The most consistent history and physical examination findings are acute-onset vomiting, diarrhea, mild obtundation, inappetence, reduced or absent anal tone, absence of pupillary light responses and lacrimal secretion, mydriasis, and protrusion of the nictitating membrane. Secondary effects of autonomic dysfunction, such as aspiration pneumonia and lethargy may develop. Weight loss is often dramatic.
Laboratory findings are nonspecific. Pharmacologic testing of the pupils is probably the best single test for confirming the diagnosis. Dilute pilocarpine (0.05% ophthalmic solution) results in rapid pupillary constriction in dogs with dysautonomia due to supersensitivity of the denervated muscle to cholinergic drugs. The prognosis is grave.
Last full review/revision July 2011 by Caroline N. Hahn, DVM, MSc, PhD, DECEIM, DECVN, MRCVS