Guillain-Barré Syndrome and Other Immune-Mediated Neuropathies¶
Chapter 458 | Part 13: Neurologic Disorders
KEY CLINICAL POINTS¶
- Guillain-Barré Syndrome (GBS) is an acute, autoimmune-mediated polyneuropathy characterized by ascending flaccid paralysis, areflexia, and autonomic dysfunction.
- Common subtypes include Acute Inflammatory Demyelinating Polyneuropathy (AIDP), Acute Motor Axonal Neuropathy (AMAN), Acute Motor Sensory Axonal Neuropathy (AMSAN), and Miller Fisher Syndrome (MFS).
- Antiganglioside antibodies (e.g., anti-GM1, anti-GQ1b) and immune-mediated complement activation are central to pathogenesis.
- Diagnosis relies on clinical presentation, CSF findings (cytoalbuminologic dissociation), and electrophysiologic studies (conduction block in demyelinating forms).
- Treatment with intravenous immunoglobulin (IVIg) or plasma exchange (PLEX) is effective, with ~85% of patients achieving full recovery within months.
1. DEFINITION & OVERVIEW¶
Guillain-Barré Syndrome (GBS) is an acute, autoimmune-mediated polyneuropathy characterized by rapid onset of flaccid paralysis, areflexia, and autonomic dysfunction. It is distinct from other immune-mediated neuropathies (e.g., CIDP, nodopathies) by its acute presentation and immune-mediated pathogenesis. GBS is classified into subtypes based on electrophysiologic and immunologic features, with AIDP being the most common variant.
Table 458-1: Subtypes of Guillain-Barré Syndrome (GBS)¶
| SUBTYPE | FEATURES | ELECTRODIAGNOSIS | PATHOLOGY |
|---|---|---|---|
| Acute Inflammatory Demyelinating Polyneuropathy (AIDP) | Adults > children; 90% in Western world; rapid recovery; anti-GM1 antibodies (<50%) | Demyelinating | First attack on Schwann cell surface; widespread myelin damage, macrophage activation, and lymphocytic infiltration; variable secondary axonal damage |
| Acute Motor Axonal Neuropathy (AMAN) | Children/youth; prevalent in China/Mexico; rapid recovery; anti-GD1a antibodies | Axonal | First attack at motor nodes of Ranvier; macrophage activation, few lymphocytes, frequent periaxonal macrophages; axonal damage variable |
| SUBTYPE | FEATURES | ELECTRODIAGNOSIS | PATHOLOGY |
|---|---|---|---|
| Acute Motor Sensory Axonal Neuropathy (AMSAN) | Mostly adults; slow recovery; closely related to AMAN | Axonal | Same as AMAN, but also affects sensory nerves and roots; axonal damage usually severe |
| Miller Fisher Syndrome (MFS) | Adults/children; ophthalmoplegia, ataxia, areflexia; anti-GQ1b antibodies (90%) | Axonal or demyelinating | Resembles AIDP; rare cases examined |
1.1 Subtypes of GBS¶
GBS subtypes include: 1) Acute Inflammatory Demyelinating Polyneuropathy (AIDP), 2) Acute Motor Axonal Neuropathy (AMAN), 3) Acute Motor Sensory Axonal Neuropathy (AMSAN), 4) Miller Fisher Syndrome (MFS), and 5) regional variants (e.g., pharyngeal-cervical-brachial neuropathy).
1.2 Pathophysiology¶
Immune-mediated damage to peripheral nerves involves complement activation, macrophage infiltration, and axonal degeneration. Antiganglioside antibodies (e.g., anti-GM1, anti-GQ1b) target Schwann cell surfaces and nodes of Ranvier, leading to demyelination or axonal injury.
2. EPIDEMIOLOGY¶
GBS occurs at a rate of 10–20 cases per million annually, with ~5000–6000 cases in the U.S. annually. Males are at slightly higher risk than females; adults are more frequently affected than children. Antecedent infections (e.g., Campylobacter jejuni, CMV, EBV) occur in ~70% of cases. Regional variants (e.g., AMAN in China) and post-vaccination associations (e.g., swine flu vaccine) are noted.
2.1 Risk Factors¶
Infections (C. jejuni, CMV, EBV), recent vaccinations (e.g., swine flu), and immune checkpoint inhibitors. Increased risk with SARS-CoV-2 vaccines (adenovirus vectors) but not mRNA vaccines.
2.2 Demographics¶
Peak incidence in adults; males > females. Regional variants (e.g., AMAN in China) and pediatric presentations (e.g., MFS).
3. ETIOLOGY & PATHOPHYSIOLOGY¶
GBS is primarily immune-mediated, with antiganglioside antibodies (e.g., anti-GM1, anti-GQ1b) targeting Schwann cell surfaces and nodes of Ranvier. Molecular mimicry between bacterial glycolipids (e.g., C. jejuni) and host gangliosides (e.g., GM1) triggers autoimmunity. Complement activation and macrophage infiltration mediate demyelination, while axonal damage occurs in AMAN/AMSAN.
Table 458-2: Principal Antiglycolipid Antibodies in Immune Neuropathies¶
| CLINICAL PRESENTATION | ANTIBODY TARGET | USUAL ISOTYPE |
|---|---|---|
| Acute Inflammatory Demyelinating Polyneuropathy (AIDP) | GM1 | IgG (polyclonal) |
| Acute Motor Axonal Neuropathy (AMAN) | GD1a, GM1, GM1b, GalNAc–GD1a | IgG (polyclonal) |
| Miller Fisher Syndrome (MFS) | GQ1b | IgG (polyclonal) |
| CLINICAL PRESENTATION | ANTIBODY TARGET | USUAL ISOTYPE |
|---|---|---|
| Acute Pharyngeal-Cervicobrachial Neuropathy (APCBN) | GT1a | IgG (polyclonal) |
| Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) | P0, myelin P2, PMP22 | IgG, IgA |
3.1 Immune Mechanisms¶
Autoantibodies (IgG) against gangliosides (GM1, GD1a, GQ1b) and complement-mediated injury at nodes of Ranvier. Molecular mimicry between bacterial glycolipids and host gangliosides (e.g., C. jejuni) drives autoimmunity.
3.2 Pathogenesis¶
Demyelination in AIDP via complement-mediated Schwann cell damage; axonal degeneration in AMAN/AMSAN. Antiganglioside antibodies (e.g., anti-GQ1b) cross-react with gangliosides at nodes and paranodes.
4. CLINICAL FEATURES¶
GBS presents with rapidly evolving flaccid paralysis, areflexia, and autonomic dysfunction. Common symptoms include ascending weakness, dysesthetic pain, and autonomic instability (e.g., hypotension, cardiac arrhythmias). Sensory involvement is variable, with dysesthesias and reduced reflexes. Complications include respiratory failure, bladder dysfunction, and prolonged ICU stays.
4.1 Symptomatology¶
Ascending flaccid paralysis, areflexia, dysesthetic pain, autonomic instability (hypotension, arrhythmias), and sensory disturbances. Pain may mimic overexertion or dysesthesias in extremities.
4.2 Complications¶
Respiratory failure (30% require ventilatory support), bladder dysfunction, autonomic instability, and prolonged ICU stays. Severe cases may progress to respiratory failure or cardiac arrhythmias.
5. DIFFERENTIAL DIAGNOSIS¶
Differential diagnoses include spinal cord disease (e.g., transverse myelitis), viral myelitis, Lyme disease, paraneoplastic syndromes, and toxic neuropathies (e.g., organophosphate poisoning). MFS must be distinguished from other paraneoplastic syndromes and autoimmune encephalitis.
5.1 Mimicking Conditions¶
Spinal cord disease (e.g., myelitis), viral encephalitis, Lyme neuroborreliosis, paraneoplastic syndromes, and toxic neuropathies (e.g., thallium, arsenic poisoning).
5.2 Red Flags¶
CSF pleocytosis (suggests infection, HIV, or malignancy), prolonged back pain with sphincter disturbances (Lyme, CMV), or focal neurological deficits (e.g., cranial nerve palsies).
6. INVESTIGATIONS & DIAGNOSIS¶
Diagnosis relies on clinical presentation, CSF findings (cytoalbuminologic dissociation), and electrophysiologic studies (conduction block in demyelinating forms). Brighton criteria classify diagnostic certainty based on clinical and electrophysiologic features.
Table 458-3: Brighton Criteria for GBS and MFS Diagnosis¶
| LEVEL OF DIAGNOSTIC CERTAINTY | CRITERIA |
|---|---|
| Level 1 | Bilateral flaccid limb weakness, decreased reflexes, monophasic illness, CSF protein elevation without pleocytosis, and electrophysiologic findings consistent with GBS |
| Level 2 | Bilateral flaccid weakness, decreased reflexes, monophasic illness, CSF <50 cells/mL, and absence of alternative diagnoses |
| Level 3 | Bilateral flaccid weakness, decreased reflexes, monophasic illness, absence of alternative diagnoses, and no CNS involvement |
6.1 CSF Findings¶
Elevated protein (1–10 g/L) without pleocytosis (cytoalbuminologic dissociation). CSF pleocytosis suggests alternative diagnoses (e.g., HIV, neurosarcoidosis).
6.2 Electrophysiologic Studies¶
Conduction block in demyelinating forms (AIDP), reduced CMAP amplitudes in axonal forms (AMAN/AMSAN), and normal SNAPs in sensory variants.
7. MANAGEMENT & TREATMENT¶
Treatment includes IVIg (2 g/kg over 5 days) or PLEX (4–6 sessions). Corticosteroids and plasma exchange are less effective. Supportive care includes ventilatory support, ICU monitoring, and physical therapy. Rituximab may be used for refractory cases.
7.1 Therapeutic Options¶
IVIg (first-line), PLEX (equally effective), corticosteroids (not recommended), and rituximab for refractory cases. Subcutaneous Ig (scIg) is an alternative for long-term management.
7.2 Supportive Care¶
Ventilatory support (30% require intubation), ICU monitoring for autonomic instability, and physical therapy to prevent contractures.
8. PROGNOSIS & COMPLICATIONS¶
Most patients (85%) achieve full recovery within months. Mortality is <5% due to respiratory failure or cardiac complications. Long-term sequelae include residual areflexia, fatigue, and sensory abnormalities. Severe cases may progress to critical illness neuropathy.
8.1 Recovery¶
Full recovery in ~85% within months; residual areflexia and fatigue may persist. Recovery is faster in AIDP than in axonal variants (AMAN/AMSAN).
8.2 Complications¶
Respiratory failure, cardiac arrhythmias, prolonged ICU stays, and secondary infections. Severe cases may develop critical illness neuropathy or myopathy.
9. SPECIAL CONSIDERATIONS¶
GBS in pregnancy is associated with increased maternal mortality; delivery may be delayed. Pediatric cases (e.g., MFS) require early recognition. Elderly patients have higher mortality due to comorbidities. Post-vaccination GBS is rare but documented with certain vaccines (e.g., swine flu).
9.1 Pregnancy¶
Increased maternal mortality; delivery may be delayed. Neonatal transfer of maternal antibodies may cause transient GBS in infants.
9.2 Pediatrics¶
MFS and regional variants (e.g., pharyngeal-cervical-brachial neuropathy) are more common in children. Early recognition is critical to avoid misdiagnosis.
10. KEY POINTS & CLINICAL PEARLS¶
- GBS is an acute autoimmune polyneuropathy with rapid onset of flaccid paralysis and areflexia. 2. AIDP is the most common subtype, while MFS is a variant with ophthalmoplegia and ataxia. 3. Antiganglioside antibodies (e.g., anti-GQ1b) are diagnostic for MFS. 4. IVIg or PLEX are first-line treatments; corticosteroids are ineffective. 5. CSF findings (cytoalbuminologic dissociation) are diagnostic. 6. Prognosis is generally favorable, with ~85% full recovery. 7. Monitor for respiratory failure and autonomic instability in ICU.