Encephalomyelopathy and polyneuropathy associated with neuronal vacuolation in two Boxer littermates.

Neuronal vacuolation and spinocerebellar degeneration is a rare, presumably inherited condition that is reported only in Rottweilers and in crossbred dogs with known or potential Rottweiler heritage. Gross and histopathologic findings include laryngeal muscle atrophy, neuronal vacuolation, and a combined central and peripheral axonopathy. Two 6-month-old Boxer puppies from the same litter were referred for evaluation of progressive pelvic limb paresis and ataxia, upper airway stridor, and visual deficits. Examination of each dog suggested a combined myelopathy and peripheral neuropathy, as well as congenital ocular disease. Gross lesions were limited to atrophy of the intrinsic laryngeal muscles. Histopathologically, there was diffuse loss of axons and myelin in the dorsolateral and ventral funiculi throughout the spinal cord and extending into the caudal aspect of the brain stem. Vacuolation of scattered neuronal cell bodies was present in the spinal cord and selected brain stem nuclei. Multifocal axonal degeneration and demyelination was observed in the recurrent laryngeal nerve, sciatic nerve, and brachial plexus and was most severe in the recurrent laryngeal nerve. Ocular abnormalities included microphthalmia, cataracts, and retinal dysplasia. The findings in these Boxer dogs, unrelated to the Rottweiler breed, are analogous to the syndrome of neuronal vacuolation and spinocerebellar degeneration reported in Rottweilers.