Spinocerebellar Ataxias

KEY FACTS

Terminology

• Spinocerebellar ataxias (SCAs)

  • Spinocerebellar atrophy; spinocerebellar degeneration

  • Previously known as Marie ataxia, inherited olivopontocerebellar atrophy, spinocerebellar degeneration

• Inherited progressive neurodegenerative disorders

  • Clinically, genetically very heterogeneous (> 60 types)

    • –

      SCA 3 most frequent subtypes

  • 2 groups: Autosomal dominant, autosomal recessive

Imaging

• General features

  • Atrophy of cerebellum, brainstem with normal cerebral hemispheres

  • Cerebellar atrophy = hallmark of cerebellar ataxias but can be mild or even absent in some

• Autosomal recessive ataxias

  • Most common = Freidreich ataxia (often not imaged)

    • –

      Cerebellum generally normal

    • –

      Spinal cord/brainstem atrophic

• Autosomal-dominant ataxias

  • Findings vary with type

  • Brainstem (pontine) > > cerebellar atrophy (often only vermis)

    • –

      Pons in SCA1, total brainstem SCA3, cerebellum in SCA6

Clinical Issues

• General = progressive cerebellar ataxia

  • Can result from both hereditary, acquired disorders

  • Phenotypes vary from predominantly cerebellar to sensorimotor neuropathy, ophthalmological disturbances, movement disorders, seizures, cognitive dysfunction, extra-CNS manifestations

• Autosomal-recessive ataxias (onset < 20 years)

  • Peripheral sensorimotor neuropathy

    • –

      Extra-CNS involvement common

  • Slowly progressive course despite early onset

• Autosomal-dominant ataxias

  • Mean age at onset = 3rd, 4th decades

  • Gait disorders, abnormal eye movements, macular degeneration

  • Progressive, often fatal (brainstem failure)

TERMINOLOGY