What are the types of Guillain-Barré Syndrome (GBS)?

Types of Guillain-Barré Syndrome

Guillain-Barré Syndrome is classified into three main electrophysiological subtypes—AIDP (acute inflammatory demyelinating polyneuropathy), AMAN (acute motor axonal neuropathy), and AMSAN (acute motor and sensory axonal neuropathy)—plus several distinct clinical variants including Miller Fisher syndrome. 1

Major Electrophysiological Subtypes

AIDP (Acute Inflammatory Demyelinating Polyneuropathy)

• AIDP is the classic demyelinating form that accounts for 90% of all GBS cases in the Western world. 2
• Electrodiagnostic studies show demyelinating features, though international consensus on specific criteria remains elusive. 1
• This subtype is associated with cranial nerve involvement in 30-50% of cases. 3
• AIDP is mediated by anti-ganglioside antibodies (particularly GM1) that damage myelin. 3

AMAN (Acute Motor Axonal Neuropathy)

• AMAN is a pure motor axonal form more prevalent in Asia, South and Central America, often preceded by Campylobacter jejuni infection. 2
• This subtype does NOT typically present with cranial nerve involvement, distinguishing it from AIDP. 3
• AMAN is mediated by anti-ganglioside antibodies (particularly GD1a) that target axons rather than myelin. 3
• AMAN may present with either reversible nerve conduction failure (RCF) or axonal degeneration, with RCF cases having better prognosis. 4

AMSAN (Acute Motor and Sensory Axonal Neuropathy)

• AMSAN features both motor AND sensory axonal damage, representing the most severe axonal subtype. 1
• This subtype is also more prevalent in Asia, South and Central America. 2
• AMSAN patients generally have more severe outcomes compared to AIDP, particularly at 3,6, and 12 months. 4

Clinical Variants

Miller Fisher Syndrome (MFS)

• Miller Fisher syndrome is characterized by the classic triad of ophthalmoplegia, areflexia, and ataxia. 1
• MFS may also present with cranial nerve dysfunction beyond ophthalmoplegia. 3
• This variant is mediated by anti-GQ1b ganglioside antibodies. 3

Regional Variants

• Pure motor variant presents with weakness without sensory signs. 1
• Bilateral facial palsy with paresthesias can occur as a regional variant. 1
• Pharyngeal-cervical-brachial weakness represents another regional pattern. 1
• Paraparetic variant affects primarily the lower extremities. 1

Critical Classification Challenges

Unclassifiable Cases

• Approximately one-third of patients cannot be classified into AIDP, AMAN, or AMSAN at initial presentation and are labeled "equivocal" or "inexcitable." 1
• Repeating electrodiagnostic studies 3-8 weeks after onset may help classify initially unclassifiable cases, though this practice remains controversial. 1
• When using nerve conduction studies to classify subtypes, the number of patients categorized as AIDP can range from 21% to 72% depending on which published criteria are applied. 5

Important Clinical Pitfall

• Do not assume normal reflexes rule out GBS—the pure motor variant and AMAN subtype can have normal or even exaggerated reflexes. 6

Treatment Implications

The treatment approach does NOT differ based on electrophysiological subtype—both IVIg and plasma exchange are first-line therapies regardless of whether the patient has AIDP, AMAN, or AMSAN. 1, 7

• The traditional demyelinating versus axonal dichotomy is increasingly challenged in clinical practice. 1
• Both plasma exchange and intravenous immunoglobulin have established efficacy in large international randomized trials across all subtypes. 2, 7