Spinal muscular atrophy in Brown Swiss calves.

Nineteen Brown Swiss calves affected with spinal muscular atrophy were described. Weakness of the rear legs was the first sign observed at 3 to 4 weeks of age. Terminal stages were characterized by severe muscular atrophy, quadriparesis, and sternal recumbency. Bronchopneumonia was a frequent complicating disease. Microscopic changes consisted mainly of degeneration and loss of motor neurons in the ventral horns of the spinal cord. Neurogenic atrophy of muscles was a constant finding. Electron microscopy revealed accumulation of neurofilaments and mitochondria in affected neurons. The disease shares many features with Werdnig-Hoffmann disease in man and the spinal muscular atrophies of other animals.