How to approach a child with focal athetosis?

Diagnostic Approach to a Child with Focal Athetosis

The evaluation of a child with focal athetosis should begin with neuroimaging, particularly brain MRI, to identify underlying structural abnormalities in the basal ganglia or other brain regions that could explain the movement disorder. 1

Initial Assessment

When evaluating a child with focal athetosis, consider the following key aspects:

• Timing of symptom onset: Acute, subacute, or chronic progression
• Distribution: Truly focal (single limb/hemibody) vs. generalized
• Associated neurological symptoms: Presence of ataxia, dystonia, chorea, or other movement disorders
• Developmental history: Regression or plateau in milestones

Neuroimaging

Brain MRI is the cornerstone of evaluation for focal athetosis:

• First-line imaging: MRI brain with contrast to evaluate for structural lesions, particularly in the basal ganglia, thalamus, and cerebellum 1
• When to consider CT: Only in acute settings when MRI is unavailable or contraindicated, as CT is less sensitive for posterior fossa abnormalities 1

Differential Diagnosis and Specific Evaluations

1. Acquired Causes

• Hypoxic-ischemic injury: Look for history of perinatal asphyxia or stroke
• Kernicterus: History of severe neonatal hyperbilirubinemia with characteristic findings (hearing loss, impaired upward gaze, dental enamel dysplasia) 2
• Post-infectious/inflammatory: Consider autoimmune encephalitis, post-streptococcal disorders
• Traumatic brain injury: History of head trauma 3
• Medication-induced: Review all medications

2. Genetic/Metabolic Disorders

• Ataxia-telangiectasia: Look for progressive cerebellar ataxia, conjunctival telangiectasias, oculomotor apraxia, and immunodeficiency 1
• Wilson's disease: Check for Kayser-Fleischer rings, liver dysfunction
• Mitochondrial disorders: Look for multisystem involvement
• Lesch-Nyhan syndrome: Self-injurious behavior, hyperuricemia

3. Structural Lesions

• Brain tumors: Particularly affecting basal ganglia or posterior fossa
• Vascular malformations: May cause focal symptoms

Laboratory Investigations

Based on clinical suspicion:

• Complete blood count
• Liver function tests
• Metabolic panel
• Alpha-fetoprotein (elevated in ataxia-telangiectasia) 1
• Copper and ceruloplasmin (for Wilson's disease)
• Thyroid function tests
• Autoimmune panels if indicated

Management Approaches

Management should target the underlying cause when identified:

1. Symptomatic treatment of movement disorder:

   • Pharmacological options:
     • Anticholinergics (trihexyphenidyl) for dystonic components
     • Dopamine antagonists for chorea
     • Benzodiazepines for severe cases

2. Focal interventions:

   • Botulinum toxin injections: Consider for focal athetosis affecting specific muscle groups to improve function and reduce pain 4

3. Rehabilitation strategies:

   • Physical therapy: Focus on stabilization exercises, closed chain activities, and functional training 5
   • Occupational therapy: For fine motor skills and activities of daily living
   • Adaptive equipment: To improve function and independence

4. Specific disease management:

   • For genetic disorders like ataxia-telangiectasia, multidisciplinary care including neurology, immunology, pulmonology, and oncology 1

Common Pitfalls and Caveats

• Misdiagnosis: Athetosis can be confused with chorea or dystonia; careful observation of the movement pattern is essential 6
• Overlooking treatable causes: Always consider reversible metabolic or toxic etiologies
• Radiation sensitivity: Children with certain disorders (e.g., ataxia-telangiectasia) have increased sensitivity to ionizing radiation, so limit CT scans 1
• Incomplete evaluation: Focal athetosis may be one component of a more complex neurological syndrome
• Treatment resistance: Movement disorders may be difficult to control; combination therapy may be needed

Follow-up Recommendations

• Regular neurodevelopmental assessments to monitor progression
• Adjustment of therapies based on response and functional goals
• Genetic counseling when hereditary disorders are identified

Remember that early identification of the underlying cause and prompt initiation of appropriate interventions are crucial for optimizing outcomes in terms of morbidity, mortality, and quality of life for children with focal athetosis.