What is the difference between Guillain‑Barré syndrome (GBS) and acute inflammatory demyelinating polyneuropathy (AIDP)?

AIDP is Not Different from GBS—It IS GBS

Acute inflammatory demyelinating polyneuropathy (AIDP) is not a separate disease from Guillain-Barré syndrome; rather, AIDP is the most common subtype of GBS itself. 111

Understanding the Relationship

GBS is an umbrella term for a group of acute immune-mediated polyneuropathies, and AIDP represents the classic demyelinating form. Think of it this way:

• GBS = The syndrome (the overall disease category)
• AIDP = The most common subtype within that syndrome

The GBS Subtypes

Electrophysiological studies distinguish between three main subtypes of GBS 111:

1. AIDP (Acute Inflammatory Demyelinating Polyradiculoneuropathy) - The demyelinating form

   • Accounts for ~90% of GBS cases in Western countries 2
   • Characterized by immune attack on Schwann cell membrane and myelin 3
   • Shows patchy demyelination throughout the peripheral nervous system 3

2. AMAN (Acute Motor Axonal Neuropathy) - Pure motor axonal form

   • More prevalent in Asia, South and Central America 24
   • Primary axonal degeneration without demyelination 3
   • Often preceded by Campylobacter jejuni infection 2

3. AMSAN (Acute Motor and Sensory Axonal Neuropathy) - Motor and sensory axonal form

   • Similar pathophysiology to AMAN but involves sensory nerves 4
   • Characterized by axonal degeneration accentuated at spinal nerve roots 3

Clinical Implications

The distinction matters primarily for understanding pathophysiology and prognosis, not for acute treatment decisions. Both AIDP and axonal forms receive identical first-line treatment 11:

• Intravenous immunoglobulin (0.4 g/kg daily for 5 days), OR
• Plasma exchange (200-250 ml/kg for 5 sessions)

Key Diagnostic Point

When you diagnose someone with "GBS," you're making the clinical syndrome diagnosis. The electrophysiological studies then subclassify whether it's AIDP (demyelinating) versus AMAN/AMSAN (axonal) 11. This subtyping helps predict recovery patterns—axonal forms may have slower recovery due to the need for axonal regeneration rather than just remyelination 3.

Common Pitfall to Avoid

Don't delay treatment waiting for electrophysiological confirmation of subtype. The clinical diagnosis of GBS should prompt immediate treatment consideration, as both AIDP and axonal variants respond to the same immunomodulatory therapies 5. Electrophysiology helps with subclassification but shouldn't gate treatment decisions in a rapidly progressing patient.

The terminology confusion arises because AIDP was historically considered synonymous with GBS before the axonal variants were recognized. Now we understand GBS as the broader syndrome encompassing multiple pathophysiological subtypes, with AIDP being the predominant one in most Western populations 62.