What is Acute Inflammatory Demyelinating Polyneuropathy (AIDP), also known as Guillain-Barré Syndrome (GBS), and its management?

What is AIDP and Key Postgraduate Knowledge

Acute Inflammatory Demyelinating Polyneuropathy (AIDP) is the most common subtype of Guillain-Barré Syndrome in Europe and North America, representing a potentially fatal immune-mediated disease with 3-10% mortality even with optimal care, requiring immediate recognition and treatment within 2 weeks for best outcomes. 1, 2

Definition and Epidemiology

• AIDP is the demyelinating form of GBS, distinguished from axonal variants (AMAN and AMSAN) by electrophysiological studies showing evidence of demyelination rather than axonal injury 1
• Global incidence is approximately 1-2 per 100,000 person-years, with male predominance and increasing incidence with age 1
• AIDP predominates in Western countries, while AMAN is more common in East Asia 3

Pathophysiology You Must Know

• The immune system attacks Schwann cells or myelin components in peripheral nerves, causing demyelination through complement activation, macrophage infiltration, and edema 1
• Unlike AMAN (where gangliosides GM1, GM1b, GD1a are targets), the exact target molecules in AIDP remain unidentified 3
• Typically triggered by preceding infections (Campylobacter jejuni, cytomegalovirus, Epstein-Barr virus, Mycoplasma pneumoniae) occurring 1-3 weeks before symptom onset 3

Clinical Presentation - What to Look For

• Classic pattern: Ascending weakness starting in legs, progressing to arms and cranial muscles over days to 4 weeks maximum 1, 3
• Sensory symptoms (paresthesias, pain) accompany motor weakness 1
• Hyporeflexia or areflexia is characteristic 4
• Critical timing: Most patients reach maximum disability within 2 weeks 1, 2

Life-Threatening Complications - Never Miss These

• Respiratory failure occurs in 20% of patients and can develop rapidly without obvious dyspnea symptoms 1, 2
• Autonomic dysfunction causes cardiac arrhythmias and blood pressure instability, contributing significantly to mortality 1, 2
• Facial palsy occurs in approximately 34% of patients 5
• Seasonal clustering in winter months has been observed 5

Diagnostic Workup

• CSF analysis: Classic finding is albuminocytologic dissociation (elevated protein with normal cell count), though this can be normal early in disease course 1
• Mean CSF protein levels around 113.8 mg/dL have been reported 5
• Electrophysiology: Shows demyelinating features including conduction block, prolonged distal latencies, and absent H-reflex in over 90% of cases 1, 5
• Erb's point stimulation for proximal nerve segment assessment has high predictive value 5

Treatment - The Critical Window

Initiate immunotherapy within the first 2 weeks of symptom onset for optimal outcomes 2

First-Line Treatment Options (Equally Effective):

• Intravenous immunoglobulin (IVIg): 0.4 g/kg/day for 5 consecutive days (total dose 2 g/kg) 2, 6
• Plasma exchange: 5 sessions at 200-250 mL/kg 6
• Both treatments work through immune modulation - IVIg via complement inactivation, antibody neutralization, cytokine inhibition, and Fc receptor saturation 3
• Corticosteroids alone are NOT effective and should not be used 6, 3

Treatment-Related Fluctuations:

• Occur in 6-10% of patients within 2 months of initial improvement 2
• Repeat treatment is commonly practiced despite uncertain efficacy when patients deteriorate after initial response 1

Monitoring Requirements

• Respiratory function monitoring is mandatory in ALL patients - use peak flow testing as a predictor for mechanical ventilation need 2, 5
• Cardiac monitoring for arrhythmias 2
• Serial neurological examinations to track progression 7

Medications to AVOID

• β-blockers, IV magnesium, fluoroquinolones, aminoglycosides, and macrolides can worsen neuromuscular function 6

Prognosis - Set Realistic Expectations

• 60-80% of patients walk independently at 6 months 1, 2
• Most extensive improvement occurs in the first year but can continue beyond 5 years 1
• Mechanical ventilation required in 38.5% of cases 5
• Mortality remains 3-10% despite optimal treatment 1, 2
• Relapses occur in 2-5% of patients 1

Common Pitfalls to Avoid

• Missing early respiratory failure - monitor respiratory function even without dyspnea symptoms 2
• Delaying treatment beyond 2 weeks significantly worsens outcomes 2
• Using corticosteroids as monotherapy (ineffective) 6, 3
• Failing to rule out GBS mimics (acute rhabdomyolysis, myopathy, critical illness polyneuropathy) 6
• Administering neuromuscular-blocking medications that can worsen the condition 6

Supportive Care Essentials

• Manage neuropathic pain with gabapentin, pregabalin, or duloxetine (avoid opioids as first-line) 6
• Treat constipation/ileus which is common 6
• ICU admission for close monitoring of respiratory and autonomic function 1