Canine Polyneuropathy

Polyneuropathy is a neurological disorder of many peripheral nerves. It usually affects both sides of the body equally. The disorder, which is sometimes called chronic relapsing polyneuropathy, is caused by damage to the fatty covering that wraps around and protects nerve fibers, called myelin sheath. The mean age of onset of clinical signs in all affected dogs is 10 to 18 months. Acute polyneuropathy may also be caused by a bacterial toxin or by an autoimmune reaction. Toxic substances, including heavy metals such as lead and mercury, carbon monoxide, and some drugs can also cause acute polyneuropathy.

Over the past decade, several breed-related peripheral neuropathies have been reported in dogs, including laryngeal paralysis-polyneuropathy complex in young Dalmatian dogs; laryngeal paralysis in young Bouvier des Flandres and Siberian Husky dogs; congenital hypomyelinating polyneuropathy in Golden Retriever puppies; spinal muscular atrophy in young Rottweilers, Brittany Spaniels, English Pointers, Swedish Laplands, German Shepherd dogs and Cairn Terriers; hypertrophic neuropathy in young Tibetan Terrier dogs; giant axonal neuropathy in young adult German Shepherd dogs; distal sensorimotor polyneuropathy in mature Rottweiler dogs; sensory neuropathies in young Boxer, English Pointer, and Dachshund dogs; globoid leukodystrophy in Cairn and West Highland White Terriers; and fucosidosis in Springer Spaniels.4 In Dalmatians and Bouvier des Flandres, generalized polyneuropathy may occur as laryngeal paralysis. The early form of this condition is as seen in young dogs with congenital or hereditary disease; the delayed-onset form is usually found in older dogs with so-called idiopathic laryngeal paralysis, some of which may have hypothyroidism.2




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Polyneuropathy is characterized by progressive weakness in the limbs, exercise intolerance, high-steppage gait, loss or change in the pitch of the bark, and difficulty breathing. The distal sensorimotor polyneuropathy affects young adult Rottweilers. Although signs may appear acutely, the course tends to be gradually progressive, up to 12 months or longer in some dogs, and may be relapsing.2 The signs include weakness of all four limbs and decreased reflexes. Treatment is possible with corticosteroids, but the prognosis is poor. The condition is believed to have similarities to hereditary motor and sensory neuropathy (HMSN) type II in humans.2

Alaskan Malamute. dog breed genetically predisposed to polyneuropathy

The cause of polyneuropathy in Alaskan Malamutes is undetermined. Dogs may not have evidence of metabolic, toxic, or autoimmune disease. The occurrence of this condition in Alaskan Malamutes strongly suggests a genetic disease. Although pedigree data are incomplete, an autosomal recessive mode of inheritance is suggested.

The polyneuropathy of juvenile Greyhound show dogs becomes clinically apparent between three to nine months of age. Owners of affected dogs report exercise intolerance and walking difficulties such as high stepping gait and bunny hopping in the early stages of the disease. In the later stages, the disease was characterized by severe muscle atrophy, ataxia and change in the pitch of the bark. After clinical signs appeared none of the animals survive longer than ten months. If not euthanized earlier on request of the owners, progression of laryngeal paresis/paralysis and phrenic neuropathy is going to inflict lethal consequences. About a quarter of all Greyhound show dogs carries the mutation for polyneuropathy.5

References

  1. Merck Manual, Home Edition. Polyneuropathy.
  2. K. G. Braund, M. Toivio-Kinnucan, J. M. Vallat, J. R. Mehta and D. C. Levesque. Distal sensorimotor polyneuropathy in mature Rottweiler dogs. Veterinary Pathology, Vol 31, Issue 3 316-326, Copyright © 1994 by American College of Veterinary Pathologists
  3. Braund KG, Steinberg HS, Shores A, Steiss JE, Mehta JR, Toivio-Kinnucan M, Amling KA. Laryngeal paralysis in immature and mature dogs as one sign of a more diffuse polyneuropathy. Neuromuscular Laboratory, College of Veterinary Medicine, Auburn University, AL 36849-3501.
  4. Kyle G. Braund, Andy Shores, Chuck T. Lowrie, H. Steven Steinberg, Michael P. Moore, Rod S. Bagley, and Janet E. Steiss. Idiopathic Polyneuropathy in Alaskan Malamutes.
  5. A Deletion in the N-Myc Downstream Regulated Gene 1 (NDRG1) Gene in Greyhounds with Polyneuropathy



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