Spinocerebellar Ataxia with Myokymia and/or Seizures

The most significant clinical sign of the disorder is cerebellar ataxia; affected dogs often also display myokymia, an involuntary quivering of a group of muscles or part of a single muscle, seizures, or both. As the disease progresses, the muscle quivering or myokymia can reach a point that dogs can overheat; seizures can also become progressively more severe.

Spinocerebellar ataxia (SCA) with myokymia, seizures, or both is a juvenile onset inherited disorder. Affected dogs usually begin to show signs between two and ten months of age.

Unless a genetic basis is suspected due to the age, breed, or history of the dog, diagnostics must be performed to rule out infectious, inflammatory, or neoplastic causes.

There is no treatment for this disorder. Certain medications may be prescribed to control symptoms.

Talk to your vet about your dog’s spinocerebellar ataxia result so you can plan ongoing care and monitoring.

Watch for signs such as unsteady movement, muscle twitching, or seizures, and contact your vet if you notice any of these changes. If a seizure occurs, make sure your dog is in a safe area away from objects they could hit, and avoid handling them until it passes.

Keep your dog’s environment calm and consistent. Use rugs or mats to prevent slipping and help them move safely around the home.

As this condition can progress over time, supportive care and a predictable routine can help keep your dog comfortable and engaged with their family.

While originally identified in Russell group Terriers, the mutation has also been identified in populations of Smooth Haired Fox Terriers, Toy Fox Terriers, and Tenterfield Terrier (in Fox Terriers the disease is termed "hereditary ataxia"). KCNJ10 is a potassium ion channel vital for maintaining a relatively unexcitable state in the central nervous system. Loss of this KCNJ10 activity leads to increased neuron excitability and firing, which accounts for the observed clinical signs of cerebellar ataxia, seizures, and myokymia. In Russell group terriers, SCA has been mapped to a mutation in the KNJ10 gene.

Penetrance: This disease is inherited in an autosomal recessive manner, meaning that affected dogs must have two copies of the mutation to show clinical signs.

Gene

KCNJ10

Inheritance type

recessive

Clinical category

Neurologic

Citations

1. Gilliam et al 2014
2. Rohdin et al 2015

• Basenji
• Chihuahua
• Wire Fox Terrier
• Jack Russell Terrier
• Parson Russell Terrier
• Russell Terrier
• Russell-type Terrier
• Smooth Fox Terrier
• Toy Fox Terrier