Hereditary cerebellar degeneration in Scottish Terriers

Background: Hereditary cerebellar degeneration is described in several dog breeds. This heterogeneous group of diseases causes cerebellar ataxia associated with cerebellar cortical degeneration. Objective: To report the clinical and histopathological features, and describe the mode of inheritance of hereditary cerebellar degeneration in Scottish Terriers. Animals: Sixty-two affected dogs recruited through the Scottish Terrier Club of America. Materials and Methods: Prospective, observational study: Owners of affected dogs were contacted for a description of clinical signs, age of onset, and disease progression. Medical records, videotapes of gait, and brain imaging were evaluated. When possible, necropsy was performed and the brain examined histopathologically. Prevalence of the disease was estimated and a pedigree analysis was performed to determine mode of inheritance. Results: Gait abnormalities were noted in the 1st year of life in 76% of dogs, and progressed slowly; only 1 of 27 dogs dead at time of writing was euthanized because of cerebellar degeneration. Clinical signs included wide based stance, dysmetria, intention tremor, and difficulty negotiating stairs and running. Cerebellar atrophy was detected on magnetic resonance imaging. On histopathological examination, there was segmental loss of Purkinje neurons, thinning of molecular and granular layers, and polyglucosan bodies in the molecular layer. Prevalence of disease was estimated at 1 in 1,335 American Kennel Club registered Scottish Terriers. Genetic analysis results are consistent with an autosomal recessive mode of inheritance. Conclusion and Clinical Importance: A hereditary cerebellar degenerative disorder with a relatively mild phenotype has emerged in the Scottish Terrier. Genetic studies are needed.