Ataxia in the Jack Russell Terrier

Cerebellar Ataxia

a.k.a. neonatal cerebellar ataxia, primary granule cell degeneration

Onset of signs – 2 weeks of age when pups begin to ambulate

Neurologic abnormalities – An uncoordinated gait, spastic in all limbs, start out as a goose-stepping stride which progresses to a stilted stride in all limbs.  Dogs develop more difficulty in forward ambulation and frequent falling.  Intention tremors (moving back and forth of the head) are associated with goal directed movements such as eating.  Abnormal eye movements (tremoring) also begin at 2 weeks of age.  The cerebellar ataxia is quite severe by 18 months of age and many dogs are euthanized.

Brain imaging – Magnetic resonance imaging shows a smaller cerebellum.

Autopsy findings – The granular layer in the cerebellum becomes depleted.  The Purkinje neurons develop vacuoles.

Pedigree studies – The inheritance pattern suggests an autosomal recessive trait.

Spinal Ataxia

a.k.a. hereditary ataxia of Jack Russell Terriers

Onset of signs – 2 to 6 months of age

Neurologic abnormalities – An uncoordinated gait initially worse in the rear limbs with goose stepping.  The gait is spastic and eventually the front legs are affected.  The falling becomes more frequent between 1 and 2 years of age. Rippling of muscles (myokymia) may occur in some dogs especially during excitement.  Myokymia looks like worm-like movements or tremors within the muscles of the limbs and face. There may be episodes of collapse, respiratory distress and overheating that occurs with the signs of rippling muscles.  Some dogs may manifest seizures.  The life expectancy is unpredictable and is dependent upon severity of the rippling muscles and seizures.  Dogs with only the spinal ataxia seem to live well with their disease.

Brain imaging – There are no obvious abnormalities

Autopsy findings – The pathologic changes include neuronal fiber loss occur in specific areas of the spinal cord and brainstem.

Pedigree studies – The inheritance pattern is an autosomal recessive trait.