Clinical features of spongy degeneration of the central nervous system in two Labrador retriever littermates.

Spongy degeneration of the CNS was diagnosed in 2 female Labrador Retriever littermates. The dogs had histories of progressive cerebellar ataxia and episodes of extreme extensor rigidity beginning at 4 and 6 months of age. One had a history of hearing difficulties. When examined at 9 months of age, both dogs had moderate ataxia and dysmetria of the head, trunk, and limbs, hyperreflexia with clonus, and extensor rigidity with episodes of exaggerated rigidity and opisthotonos. One dog was euthanatized and the other was monitored for 2 months, during which time her signs progressed to severe dysmetria, weakness, muscle atrophy, and rigidity with marked hyperreflexia. Necropsy of both dogs revealed astrocytic abnormalities and spongy degeneration of the white matter of the CNS. The clinical signs and postmortem findings were similar to the juvenile form of spongy degeneration in man.