Cerebellar ataxia (CA1)

In the breed Belgian Shepherd, a Cerebellar Ataxia (CA1) causing, autosomal recessive variant in the RALGAPA1 gene has been identified. Affected puppies develop cerebellar dysfunction and are less active and alert compared to healthy littermates. The puppies show a wide-based stance and ataxic gait, exaggerated gait movements as well as stumbling, staggering and intention tremor of the head. Mild proprioceptive deficits can also be detected and the occulovestibular response seems to be normal to reduced. Clinical examinations of cerebrospinal fluid and blood remain unremarkable. CA1 has an early onset of around 4 weeks of age, when the activity and mobility of the puppies increases. In some cases, the cerebellar symptoms were slowly progressive, requiring the puppies to be euthanized due to the severity of the symptoms at the age of 5 weeks. In other cases, the clinical signs were stable until the age of 11 week and the dogs reached adulthood without obvious worsening of the symptoms.

In Great Pyrenees dogs, an autosomal recessive variant in the SACS gene was identified that causes Cerebellar Ataxia with an onset at around 4 months of age. First clinical signs are clumsiness, uncoordinated behavior, and difficulties when walking on slippery surfaces. Affected puppies are reluctant to climb or descend stairs and often look for fences or walls to lean against while walking and choose to lie down if possible (e.g., when eating). Symptoms are slowly progressive over time leading to neuromuscular weakness as predominant sign. Exercise does not lead to worsening of the symptoms. Blood screenings showed no abnormalities. MRI and also pathological examinations revealed a noticeable diminished size of the cerebellum. Most dogs were euthanized by 4-7 years of age.