Neuromyotonia in a Dachshund with Clinical and Electrophysiological Signs of Spinocerebellar Ataxia

A 10-month-old dachshund was presented with a recent history of episodic muscle rippling and generalised stiffness. An uncoordinated gait was present since eight weeks of age. On presentation the dog showed cerebellar-like ataxia and poor menace responses. Myokymic contractions were visible in the appendicular and truncal muscles and neuromyotonic discharges were detected by electromyography. Central components of the brain auditory evoked potentials were absent and the onset latencies of the tibial sensory-evoked potentials recorded at the lumbar intervertebral level were delayed. Response to slow-release phenytoin was temporary. The clinical picture together with the electrophysiological findings in this dachshund are identical to the findings in Jack Russell terriers with hereditary ataxia and neuromyotonia. This is the first description of neuromyotonia associated with clinical and electrophysiological signs of spinocerebellar ataxia in a breed other than the Jack Russell terrier. This case also strengthens the theory that spinocerebellar ataxia and neuromyotonia are related. An ion channel dysfunction is presumed to link both disorders.