What is ataxia?

Ataxia: Definition, Causes, and Clinical Manifestations

Ataxia is a neurological sign characterized by loss of coordination of voluntary muscle movements due to dysfunction in one or more components of the nervous system. 1 This condition manifests primarily as impaired coordination of movement, resulting in a wide-based, unsteady gait and poor coordination of the extremities.

Key Clinical Manifestations

• Gait abnormalities: Wide-based, unsteady walking pattern
• Poor limb coordination: Difficulty with fine motor tasks
• Dysmetria: Inability to judge distance and range of movement
• Dysdiadochokinesis: Impaired ability to perform rapid alternating movements
• Nystagmus: Involuntary eye movements
• Dysarthria: Slurred or impaired speech

Anatomical Origins of Ataxia

Ataxia can result from dysfunction in several neurological structures:

1. Cerebellum: Primary site affecting neural information integration, coordination, and planning 1

   • Truncal ataxia and titubation (rhythmic nodding/swaying) typically indicate midline cerebellar involvement
   • Cerebellar ataxia presents with irregular stepping patterns, variable step length/timing, and lateral veering 2

2. Spinal cord and peripheral sensory nerves: Affecting proprioception 1, 3

   • Sensory ataxia worsens when eyes are closed (positive Romberg test) 3
   • Often accompanied by weakness, hyperreflexia, spasticity, and sensory loss

3. Vestibular system: Affecting balance and equilibrium 1

   • Often presents with nausea, vomiting, and vertigo
   • A lurching gait triggered by head rotation is typical of vestibular dysfunction 1

4. Cerebral structures: Ataxia with hemiparesis can result from cerebral infarcts involving the thalamus, pons, corona radiata, or internal capsule 1

Etiological Classification

1. Acute Ataxia

• Develops within hours or days (typically within 72 hours) 1
• Common causes:
  • Trauma
  • Stroke
  • Infection (acute cerebellitis)
  • Toxins/medications
  • Post-infectious inflammatory conditions

2. Chronic/Progressive Ataxia

• Persists longer than 2 months 1
• Common causes:
  • Hereditary ataxias (spinocerebellar ataxias, Friedreich ataxia)
  • Paraneoplastic syndromes
  • Multiple sclerosis
  • Metabolic disorders
  • Chronic alcoholism

3. Episodic/Intermittent Ataxia

• Recurrent episodes with normal function between attacks
• May indicate:
  • Migraine variants
  • Benign positional vertigo
  • Intermittent metabolic disorders
  • Genetic episodic ataxias

Diagnostic Approach

The American College of Radiology recommends appropriate neuroimaging based on clinical presentation 1:

• MRI brain: Preferred for most ataxia evaluations (especially suspected cerebellar pathology)
• CT head: May be used in acute settings, trauma, or when MRI is contraindicated
• Specialized imaging: May include MR spectroscopy, diffusion tensor imaging, or functional MRI in specific cases

Clinical Pearls and Pitfalls

• Pure cerebellar ataxia is rare; associated symptoms and signs almost always exist to suggest an underlying cause 4, 5
• Several treatable forms of ataxia exist (vitamin E deficiency, cerebrotendinous xanthomatosis, Refsum disease, coenzyme Q10 deficiency) 6
• "Pseudoataxia" may occur with functional disorders or weakness conditions that mimic true ataxia 1
• Proper identification of gait pattern is crucial as it helps narrow the differential diagnosis, guides appropriate imaging, informs fall risk assessment, and directs specialist referrals 2

Understanding the specific type and cause of ataxia is essential for appropriate management and treatment planning, with particular attention to potentially treatable or reversible etiologies.