Lower Motor Neuron Disease
History. A 2-year-old male German short-haired pointer was admitted to the local veterinary clinic. His vaccinations were current, and the dog had no history of contributing prior illness.
A few days before admission, the dog had a fight with a skunk. For 48 hours before admission, an ascending paralysis developed, characterized initially by weakness and then by the lack of voluntary movement, of first the back legs and then the front legs. No barking was noticed during the illness. The dog was able to control his bladder and bowel and to move his head.
Clinical Examination. On admission, the dog was unable to bear weight on any of his four legs. Other than an elevated respiratory rate, physical examination deficits were limited to the nervous system. The dog was able to eat, drink, and move his head. A severe paralysis was noted in all legs, and no motor response to a toe pinch or tapping of the quadriceps tendon could be elicited. There was widespread atrophy of the muscles of all four legs, as well as those of the thorax and abdomen. The dog did seem to be aware of painful stimuli (deep pain response). There were no cranial nerve deficits. Results of routine blood cell counts and serum chemistry results were within normal limits.
Comment. Generalized atrophy, paralysis, and loss of segmental reflexes indicate widespread, bilateral loss of lower motor neuron function. Fortunately, the disease has spared the muscles of the head and the diaphragm, although the dog’s elevated respiratory rate indicates an attempt to compensate for paralysis of some of the respiratory muscles. A clinical diagnosis of polyradiculoneuritis (“coonhound paralysis”) was made. This disease is often preceded by the bite of another animal. Pathological changes are found predominantly in the ventral roots of the spinal cord, where the axons of the lower motor neurons leave the spinal cord. The dorsal roots are usually spared, which explains this dog’s apparent ability to feel pain. The clinical signs are those of widespread lower motor neuron disease. The syndrome resembles Guillain-Barre syndrome in humans, and both syndromes have been suggested to be autoimmune in origin.
Treatment. Animals with this form of paralysis usually recover spontaneously. Good nursing care is essential during the illness. A respirator may be necessary temporarily if respiratory paralysis occurs.