ADULT-ONSET MOTOR-NEURON DISEASE IN 3 CATS

Motor neuron diseases of domestic animals have rarely been described. Three cats with adult-onset, chronic, progressive generalized muscle w eakness characterized initially by trembling on exertion and later by extreme difficulty in walking, cervical ventroflexion, dysphagia, and marked muscle atrophy were elevated. Spinal reflexes were evident earl y but were nondetectable as the disease progressed. Electromyography r evealed fibrillation potentials, with nerve conduction velocities with in the reference range. Histologic examination of muscle specimens rev ealed denervation. Marked neuron loss and gliosis were detected in the ventral horns of the spinal cord, with atrophy of ventral nerve rootl ets. Less dramatic neuron loss was seen in brain stem motor nuclei. El ectron microscopic examination of the ventral horns disclosed hypertro phied astrocytes, with densely arrayed intermediate filaments, swollen axons with large filamentous accumulations, and many macrophages with lipofuscin-like inclusions. Clinical and pathologic findings were con sistent with a progressive neurodegenerative disease affecting spinal and some bulbar motor nuclei.