What is cerebellar ataxia?

Cerebellar Ataxia

Cerebellar ataxia is a neurological disorder characterized by impaired coordination of voluntary movements due to dysfunction of the cerebellum and/or its connections, resulting in unsteadiness, incoordination, and loss of normal motor control. 1

Definition and Pathophysiology

• Cerebellar ataxia refers to incoordination of voluntary movements due to cerebellar damage, manifesting as disequilibrium (sensation of imbalance, unsteadiness, or instability) along with loss of muscle coordination 2
• Unlike proprioceptive ataxia, cerebellar ataxia shows unsteadiness that does not significantly worsen with eye closure (negative Romberg test) 1, 3
• The cerebellum plays a crucial role in coordinating voluntary movements, and damage disrupts the ability to coordinate the relative activity of multiple muscles 4

Clinical Manifestations

• Cardinal features include:

  • Truncal ataxia (difficulty maintaining posture) - particularly common with cerebellar vermian pathology 1
  • Wide-based, unsteady, and irregular gait 5
  • Dysmetria (inability to judge distance and range of movement) 6
  • Dysdiadochokinesia (inability to perform rapid alternating movements) 6
  • Dysarthria (slurred speech) 7
  • Nystagmus and other ocular motor abnormalities 6
  • Hypotonia (decreased muscle tone) 6

• Cerebellar ataxia can be distinguished from sensory ataxia as it persists regardless of visual input (does not worsen with eye closure) 1, 4

Classification and Etiology

• Cerebellar ataxia includes various clinical conditions characterized by neurodegeneration of the cerebellum and/or brainstem 2
• Etiological classification includes:
  • Inherited forms: autosomal dominant spinocerebellar ataxias, autosomal recessive, congenital, mitochondrial, and X-linked types 2
  • Sporadic forms: toxic/nutritional, immune-mediated, infectious, and degenerative causes 2
  • Paraneoplastic cerebellar degeneration (associated with tumors) 2
  • Vascular causes (vertebrobasilar insufficiency, stroke) 2

Diagnostic Approach

• Diagnosis relies on a combination of history, thorough clinical neurological examination, imaging, and confirmatory laboratory/genetic testing 2
• MRI of the head without IV contrast is the preferred initial imaging modality for evaluating cerebellar ataxia 1
• Imaging aims to detect:
  • Parenchymal injury (volume loss or signal alterations) 2
  • Abnormal iron deposition or calcification in specific forms of ataxia 2
  • Non-degenerative causes such as mass lesions or infarcts 2
• Patterns of parenchymal injury may suggest specific ataxia subtypes, though there is significant overlap of imaging features among various etiologies 2
• Conventional neuroimaging may be unremarkable in early disease 2

Management Considerations

• Treatment approaches include:
  • Balance and postural training programs to improve stability 1
  • Task-oriented upper limb training to improve reaching and fine motor control 1
  • Prescription of appropriate assistive devices and orthoses to improve balance and mobility 1
  • Specific treatments for underlying causes when identified (e.g., immune therapies for autoimmune ataxias) 2

Clinical Pearls and Pitfalls

• Some patients with cerebellar ataxia may have coexisting symptoms of central or peripheral vestibulopathy, which can complicate the clinical picture 2
• The Romberg test cannot be properly performed in cerebellar ataxia as unsteadiness is present regardless of visual input 1
• Associated brainstem involvement should be evaluated in many forms of cerebellar ataxia 1
• Adult-onset sporadic ataxia encompasses a heterogeneous group of etiologies, requiring thorough investigation 2