Search

Generalized neuromuscular (lower motor neuron; LMN) diseases include those that affect neurons (neuronopathies), peripheral nerves (neuropathies), neuromuscular junctions (junctionopathies), and muscles (myopathies). These diseases cause diffuse clinical signs of LMN involvement. Although neuromuscular diseases occur relatively commonly in dogs, few syndromes have been well characterized in cats. Representative diseases within each of the major anatomic subcategories of neuromuscular disease are discussed.

A young cat had signs of tetraparesis that progressed to tetraplegia within a few weeks. Clinically, there was lower motor neuron disease with areflexia and muscle atrophy in all limbs. Degeneration of the motor neurons in the spinal cord was seen on histological examination. Ultrastructurally, the degeneration of nerve cells was characterized by abnormal proliferation of neurofilaments. These findings were compared to other motor neuron diseases and neurofibrillary accumulations in man and animals.

A spontaneous neurologic disease occurred in six 5 weeks old Yorkshire pigs of both sexes from four litters sired by one boar. Clinically, the disease was characterized initially by bilateral posterior ataxia and weakness which rapidly progressed to tetraplegia by 10 weeks of age. By light microscopy, there was bilateral neuronal chromatolysis, degeneration and loss restricted to motor nuclei in the ventral horns of the spinal cord, in the medulla oblongata and midbrain. In addition to diffuse Wallerian-type degeneration in the spinal cord white matter and ventral peripheral nerve roots, there was prominent neurogenic atrophy of skeletal muscle. Ultrastructurally, the perikaryon and processes of affected neurons contained massive accumulations of single 10 nm diameter neurofilaments. Copper concentrations of both the commercially prepared ration and the livers were within normal limits.