Polyneuropathy in dogs and cats is a collection of
peripheral nerve disorders that often are breed-related in these
animals. Polyneuropathy indicates that multiple nerves are involved,
unlike mononeuropathy. Polyneuropathy usually involves motor nerve
dysfunction, also known as lower motor neuron disease. Symptoms
include decreased or absent reflexes and muscle tone, weakness, or
paralysis. It often occurs in the rear legs and is bilateral. Most are
chronic problems with a slow onset of symptoms, but some occur suddenly.
Most common types of polyneuropathy
Birman
Cat distal polyneuropathy - This is an inherited disorder. Symptoms
start at the age of 8 to 10 weeks, and include frequent falling and walking
on the hocks. The
prognosis
is poor.
Botulism - Symptoms include weakness, difficulty eating,
facial nerve paralysis, and megaesophagus.
Dancing Dobermann disease - This primarily affects the
gastrocnemius muscle in Dobermanns. It usually starts between the ages of 6 to 7 months. One
rear leg will flex while standing. Over the next few months it will begin to
affect the other rear leg. Eventually, the dog is alternatively flexing and
extending each rear leg in a dancing motion. Dancing Dobermann disease
progresses over a few years to rear leg weakness and muscle atrophy. There
is no treatment, but most dogs retain the ability to walk.
Distal symmetric polyneuropathy - Symptoms include atrophy of the
distal leg muscles and the muscles of the head, and rear limb weakness.
There is no treatment and the prognosis is poor.
Dysautonomia - This is primarily seen in cats. Symptoms include
vomiting, depression, not eating, weight loss, dilated pupils,
third eyelid protrusion, sneezing, slow heart rate, and megaesophagus.
There is a poor prognosis and supportive treatment is necessary. Cats can
recover, but it may take up to one year.
Giant axonal neuropathy - This is a rare disease in the
German Shepherd Dog. It usually becomes evident between the ages of 14
and 16 months. Symptoms include rear limb weakness, decreased reflexes,
muscle atrophy, megaesophagus, and loss of bark. There is no treatment and a
poor prognosis.
Hyperchylomicronemia or
hyperlipoproteinemia - This a type of hyperlipidemia that is inherited
in cats. Polyneuropathy is caused by stretching or compression of nerves
near bone by xanthomas, which are lipid deposits. It can cause Horner's
syndrome, facial nerve paralysis, and femoral nerve, tibial nerve, radial
nerve, trigeminal nerve, or recurrent laryngeal nerve paralysis.
Hypertrophic neuropathy - This is also known as canine inherited
demyelinative neuropathy (CIDN) and is inherited in the
Tibetan Mastiff. Symptoms usually start between the ages of 7 to 10
weeks, and include weakness, decreased reflexes, and loss of bark. There may
be a poor gait or an inability to walk. There is no treatment and a guarded
prognosis.
Hypoglycemia - Polyneuropathy is especially seen in conjunction with
insulinoma.
Myasthenia gravis
Polyradiculoneuritis - This is inflammation of the nerve roots. The
most common type is
Coonhound
paralysis. This is similar to
Guillain-Barr syndrome in humans. Coonhound paralysis seems to be secondary
to a raccoon bite, probably due to some factor in the saliva. It can happen
in other breeds of dogs, also. Symptoms start 7 to 11 days after the bite,
and include rear leg weakness progressing rapidly to paralysis, and
decreased reflexes. Severe cases will have a loss of bark, trouble
breathing, and an inability to lift the head. There is a duration of 2 to 3
months for the disease. Treatment is proper nursing care, and the prognosis
is good in mild cases. Polyradiculoneuritis can also be caused by
toxoplasmosis.
Rottweiler distal sensorimotor polyneuropathy - The symptoms include
weakness of all four legs and decreased reflexes. The disease is gradually
progressive. There is a possible treatment with
corticosteroids, but the prognosis is poor.
Sensory neuropathies - These are inherited conditions in dogs and
cause an inabilty to feel pain and a loss of
proprioception. Self mutilation is often seen. There is no treatment,
and the prognosis is poor in severe cases.
Spinal muscular atrophy - This occurs in dogs and is caused by the death
of nerve cells in the spinal cord. This progressive disease has no treatment
and a poor prognosis.
Tick paralysis - This occurs in dogs; cats seem to be resistant. The
cause is a
neurotoxin in the saliva of certain species of adult ticks. Dermacentor
species predominate as a cause in North America, while Ixodes mainly causes the disease in Australia. There is a gradual
onset of symptoms, which include incoordination progressing to paralysis,
changed voice, and difficulty eating. Death can occur secondary to paralysis
of the respiratory muscles, but in North America there is a good prognosis
once the ticks are removed. Recovery is usually in 1 to 3 days. In
Australia, however, it is a more severe disease with
cranial nerve effects, and death can occur in 1 to 2 days.
Toxic neuropathies - The most common causes are
vincristine, thallium, and lead.
References
Chrisman, Cheryl; Clemmons, Roger; Mariani, Christopher; Platt, Simon
(2003). Neurology for the Small Animal Practitioner(1st ed.). Teton
New Media.
ISBN 1-893441-82-2
Ettinger, Stephen J.;Feldman, Edward C.(1995).Textbook of Veterinary
Internal Medicine(4th ed.). W.B. Saunders Company.
ISBN 0-7216-6795-3
