What is ataxia?

What is Ataxia?

Ataxia is a neurological sign characterized by loss of coordination of voluntary movements due to dysfunction of one or more components of the nervous system. 1

Definition and Manifestations

Ataxia presents with several key clinical features:

• Wide-based, unsteady gait and poor coordination of extremities
• Dysmetria (inability to accurately control the range of movements)
• Dysdiadochokinesis (inability to perform rapid alternating movements)
• Nystagmus (involuntary eye movements)
• Dysarthria (slurred speech)
• Titubation (rhythmic nodding or swaying of the head or body)

Anatomical Origins

Ataxia can result from dysfunction in several neurological structures:

1. Cerebellum: Primary site affecting neural information integration, coordination, and planning of movements 1
2. Spinal cord and peripheral sensory nerves: Affecting proprioception (position sense)
3. Vestibular system: Affecting balance and equilibrium maintenance
4. Cerebral structures: Lesions in the thalamus, pons, corona radiata, or internal capsule can cause ataxia with hemiparesis 1

Clinical Patterns and Localization

Different patterns of ataxia help localize the lesion:

• Truncal ataxia and titubation: Typically associated with midline cerebellar (vermian) pathology 1
• Sensory ataxia: Characterized by positive Romberg test (worsening with eyes closed), associated with sensory loss, hyporeflexia, and often weakness 1, 2
• Vestibular ataxia: Often accompanied by nausea, vomiting, vertigo, and lurching gait triggered by head rotation 1
• Cerebellar ataxia: Features poor coordination, dysmetria, and intention tremor without sensory loss 1

Etiologies

Ataxia can result from numerous causes:

Acute/Subacute Causes

• Trauma: Head injury affecting cerebellum or brainstem
• Stroke: Especially affecting cerebellar or brainstem circulation
• Infections: Cerebellitis, meningitis, encephalitis
• Toxins/Medications: Alcohol, anticonvulsants, chemotherapy agents, metronidazole
• Inflammatory: Multiple sclerosis, acute disseminated encephalomyelitis
• Paraneoplastic syndromes: Anti-Yo, anti-Hu antibodies

Chronic/Progressive Causes

• Genetic disorders: Spinocerebellar ataxias, Friedreich ataxia, ataxia-telangiectasia, fragile X-associated tremor/ataxia syndrome 3
• Metabolic disorders: Vitamin E deficiency, Wilson's disease
• Structural lesions: Posterior fossa tumors, Chiari malformation
• Degenerative diseases: Multiple system atrophy, cerebellar degeneration
• Toxic-metabolic: Chronic alcohol abuse, mercury poisoning

Diagnostic Approach

Imaging plays a critical role in diagnosis:

• MRI brain with contrast: Most sensitive initial test for suspected intracranial causes 1
• CT head: Useful in acute trauma settings or when MRI is contraindicated
• Spine imaging: Indicated when spinal pathology is suspected

Common Pitfalls in Diagnosis

1. Failing to recognize mimics: Weakness, hypotonia, and functional disorders can mimic ataxia 1
2. Missing treatable causes: Always consider reversible etiologies (toxins, vitamin deficiencies, infections)
3. Overlooking associated symptoms: Pure ataxia is rare; associated symptoms often point to specific diagnoses 4
4. Delayed genetic testing: Many hereditary ataxias now have identifiable genetic mutations 3

Management Considerations

Management depends on the underlying cause:

• Treat reversible causes (toxin removal, vitamin supplementation)
• Symptomatic management for coordination difficulties
• Physical therapy focusing on balance and coordination
• Genetic counseling for hereditary forms
• Avoidance of rapid multijoint movements in favor of slower, single-joint movements 2

Ataxia represents a complex neurological manifestation requiring thorough evaluation to determine the underlying cause and appropriate management strategy.