What are the differences in presentation and management of Guillain-Barré Syndrome (GBS) and viral myositis in children?

Guillain-Barré Syndrome vs Viral Myositis in Children: Differences in Presentation and Management

Guillain-Barré Syndrome (GBS) and viral myositis are distinct neurological conditions with different pathophysiology, clinical presentations, and management approaches, with GBS requiring immunotherapy (IVIg or plasma exchange) while viral myositis typically resolves with supportive care alone.

Clinical Presentation Differences

Guillain-Barré Syndrome

• Pattern of weakness: Progressive bilateral ascending weakness, typically starting in lower limbs and moving upward 1
• Reflexes: Absent or decreased tendon reflexes in affected limbs 2
• Symmetry: Relatively symmetrical weakness 1
• Sensory symptoms: May have mild sensory symptoms or signs 1
• Cranial nerve involvement: Present in 30-50% of cases, especially in AIDP subtype 1
• Pain: Often severe and may precede weakness 1
• Autonomic dysfunction: Common (blood pressure/heart rate instability, pupillary, bowel/bladder dysfunction) 2
• Time course: Reaches maximum disability within 2 weeks; if progression occurs within 24 hours or after 4 weeks, consider alternative diagnoses 2
• Preceding event: About two-thirds report infection in the 6 weeks before onset, commonly Campylobacter jejuni 2

Viral Myositis

• Pattern of weakness: Typically affects lower limbs with muscle pain and tenderness 2
• Reflexes: Usually preserved 2
• Symmetry: Often symmetrical but can be asymmetrical
• Sensory symptoms: Typically absent
• Cranial nerve involvement: Rare
• Pain: Prominent muscle pain and tenderness is characteristic
• Autonomic dysfunction: Uncommon
• Time course: Rapid onset following viral illness, typically resolves within days to weeks
• Preceding event: Almost always follows a viral respiratory or gastrointestinal infection, commonly influenza virus 2

Diagnostic Approach

Guillain-Barré Syndrome

1. CSF analysis: Albuminocytologic dissociation (elevated protein with normal cell count), though protein may be normal in 30-50% in first week 1
2. Electrodiagnostic studies: Show reduced conduction velocities, reduced sensory/motor evoked amplitudes, and abnormal temporal dispersion 1
3. Clinical criteria: Progressive bilateral weakness, absent/decreased reflexes, relative symmetry of symptoms 1

Viral Myositis

1. Laboratory findings: Elevated creatine kinase (CK) levels
2. Clinical presentation: Acute onset muscle pain and weakness following viral illness
3. Normal neurological examination: Apart from muscle tenderness and weakness

Management Differences

Guillain-Barré Syndrome

• Immunotherapy: Required for patients unable to walk independently
  • First-line: Intravenous immunoglobulin (IVIg) at 0.4 g/kg/day for 5 consecutive days 1, 3
  • Alternative: Plasma exchange (12-15 L in 4-5 exchanges over 1-2 weeks) 1
• Supportive care: Respiratory monitoring, autonomic dysfunction management, pain control
• Rehabilitation: Critical for recovery 4
• Corticosteroids: Not recommended as monotherapy 1

Viral Myositis

• Supportive care: Rest, hydration, analgesics
• No specific immunotherapy needed: Self-limiting condition
• Monitoring: For rare complications like rhabdomyolysis
• Activity: Gradual return to activities as symptoms improve

Prognosis

Guillain-Barré Syndrome

• 60-80% of patients walk independently 6 months after onset 1
• Recovery can continue for more than 3 years 1
• 20% still unable to walk after 6 months 1
• Mortality rate: 3-10% despite optimal treatment 1
• Recurrence rate: 2-5% 1

Viral Myositis

• Excellent prognosis with complete recovery within days to weeks
• Rarely recurs
• Very low mortality

Special Considerations in Children

Guillain-Barré Syndrome

• Young children (<6 years) may present with atypical features: poorly localized pain, refusal to bear weight, irritability, meningism, unsteady gait 2
• Pure motor variant occurs in 5-15% of cases 1
• Miller Fisher variant (ophthalmoplegia, areflexia, ataxia) more common in Asian populations 2

Viral Myositis

• More common in children than adults
• Often follows influenza A or B infection
• Predominantly affects calf muscles causing difficulty walking
• Typically resolves within a week

Clinical Pitfalls and Caveats

1. Diagnostic challenges:

   • GBS can be misdiagnosed as viral myositis in early stages
   • Both can present with difficulty walking and pain

2. Management errors:

   • Delaying immunotherapy in GBS can worsen outcomes
   • Unnecessary immunotherapy in viral myositis wastes resources

3. Key distinguishing features:

   • Reflexes: Absent/decreased in GBS, preserved in myositis
   • CSF: Albuminocytologic dissociation in GBS, normal in myositis
   • CK levels: Normal or slightly elevated in GBS, markedly elevated in myositis
   • Time course: Progressive over days in GBS, rapid onset and resolution in myositis

4. Respiratory monitoring:

   • Critical in GBS (15% of children develop respiratory failure) 5
   • Rarely needed in viral myositis

By understanding these key differences, clinicians can accurately diagnose and appropriately manage these distinct conditions, optimizing outcomes for pediatric patients.