Dogs with dysautonomia commonly develop progressive vomiting, diarrhea, listlessness, inappetence, decreased or absent anal tone, dysuria, mydriasis, and nictitating membrane protrusion. Diagnosis is made on the basis of history, clinical signs, and autonomic nervous system function testing. The etiology is unknown, and the prognosis is grave.
Canine dysautonomia is a degenerative polyneuropathy characterized by neuronal degeneration within the autonomic, somatic, central, peripheral, or enteric nervous system, causing multisystemic effects similar, if not identical, to dysautonomia in horses, cats, rabbits, and hares.
Canine dysautonomia was first described in England in 1983 but is uncommon now. Although individual cases have been reported in a number of European countries, canine dysautonomia is more commonly reported in the US, with most cases found in the Midwest, including Missouri, Kansas, and surrounding areas.
Clinical Findings of Canine Dysautonomia
Canine dysautonomia typically appears to affect younger dogs, and dogs from rural environments are overrepresented.
Commonly reported clinical signs and general physical examination findings associated with canine dysautonomia include the following:
vomiting
diarrhea
depression
inappetence
decreased or absent anal tone
dysuria
Absence of pupillary light reflexes with intact vision, mydriasis, decreased corneal sensitivity, and nictitating membrane protrusion are frequent neurological findings (see canine dysautonomia image).
Courtesy of Dr. Caroline Hahn.
Secondary effects of autonomic dysfunction, such as aspiration pneumonia and lethargy, may develop. Weight loss is often dramatic.
Lesions
Neuronal chromatolysis is typically found in the autonomic ganglia, brainstem nuclei, and ventral horns of the spinal cord.
Diagnosis of Canine Dysautonomia
Physical clinical signs of autonomic nervous system dysfunction
Pharmacological testing
There is no definitive agreement on criteria for diagnosing canine dysautonomia, and laboratory findings are nonspecific; however, antemortem diagnosis is typically made via documentation of physical clinical signs of autonomic nervous system dysfunction as well as pharmacological testing.
Radiographic findings of aspiration pneumonia, megaesophagus, functional ileus of the GI tract, and urinary bladder distention, or findings of decreased cardiac contractility on echocardiogram, are frequently found in cases of canine dysautonomia.
Pharmacological testing of the pupils is probably the best single test to confirm the diagnosis of canine dysautonomia; pupil constriction within 60 minutes after application of dilute pilocarpine (0.05%–0.1% ophthalmic solution) is supportive. A Schirmer tear test may show partial or complete loss of tear production bilaterally (< 5 mm/min, reference range 15–20 mm/min).
Treatment and Prognosis of Canine Dysautonomia
There is no effective treatment for canine dysautonomia. Supportive care can include IV fluid therapy; regular bladder expression; artificial tear application; and administration of metoclopramide, ranitidine, and omeprazole.
Key Points
Canine dysautonomia is a sporadic, progressive disease of unknown etiology that results in progressive degeneration of the autonomic nervous system and has a grave prognosis.
For More Information
Hull NC, O'Toole DO, Miller MM, et al. Canine dysautonomia in a litter of Havanese puppies. J Vet Diagn Invest. 2015;27(5):627-631. doi:10.1177/1040638715595838
Also see pet health content regarding dysautonomia in dogs.
