Alaskan Husky encephalopathy - a canine neurodegenerative disorder resembling subacute necrotizing encephalomyelopathy (Leigh syndrome)

The gross and histopathological findings in the brain and spinal cord of fi ve Alaskan Husky dogs with a novel incapacitating and ultimately fatal fami lial and presumed hereditary neurodegenerative disorder are described. Four dogs presented with neurological deficits before the age of 1 year (7-11 m onths) and one animal at 2.5 years old. Clinical signs in all dogs were of acute onset and included ataxia, seizures, behavioral abnormalities, blindn ess, facial hypalgesia and difficulties in prehension of food. Tn animals a llowed to survive, the disease was static but with frequent recurrences. Pa thological findings were limited to the central nervous system. Grossly vis ible bilateral and symmetrical cavitated foci were consistently present in the thalamus with variable extension into the caudal brain stem. Microscopi c lesions were more widespread and included foci of bilateral and symmetric al degeneration in the basal nuclei, midbrain, pens and medulla, as well as multifocal lesions at the base of sulci in the cerebral cortex and in the gray matter of cerebellar folia in the ventral vermis. Neuronal loss with c oncomitant neuronal sparing, spongiosis, vascular hypertrophy and hyperplas ia, gliosis, cavitation and transient mixed inflammatory infiltration were the main histopathological findings. Tn addition, a population of reactive gemistocytic astrocytes with prominent cytoplasmic vacuolation was noted in the thalamus. Lesions of this nature in this distribution within the neuro axis have not been reported in dogs. The neuropathological findings resembl e Leigh's disease/subacute necrotizing encephalomyelopathy of man. Neuronal sparing in conjunction with apparently transient astrocytic vacuolation po int to the possible pathogenetic role of astrocytes in the evolution of the se lesions. An inherited metabolic derangement of unknown nature is postula ted as the cause of this breed-specific disorder.