Signs, Symptoms, and Etiology of Guillain-Barré Syndrome
Guillain-Barré syndrome (GBS) is characterized by rapidly progressive bilateral weakness typically starting in the legs and ascending to the arms and cranial muscles, accompanied by decreased or absent reflexes, often preceded by an infection within 6 weeks of symptom onset. 1, 2
Clinical Presentation
Classic Signs and Symptoms
- Bilateral ascending weakness, typically starting in the legs and progressing to the arms and cranial muscles 1, 2
- Distal paresthesias or sensory loss that precede or accompany weakness 1, 2
- Decreased or absent reflexes in most patients at presentation and almost all patients at nadir 1
- Pain (muscular, radicular, or neuropathic) is frequently reported and can be an early symptom 1, 3
- Dysautonomia including blood pressure/heart rate instability, pupillary dysfunction, and bowel/bladder dysfunction 1
- Acute or subacute onset with maximum disability typically reached within 2 weeks 1
Atypical Presentations
- Weakness and sensory signs may be asymmetrical or predominantly proximal/distal 1
- Weakness can start in the legs, arms, or simultaneously in all limbs 1
- Severe and diffuse pain or isolated cranial nerve dysfunction may precede weakness 1
- In young children (<6 years), presentation may include poorly localized pain, refusal to bear weight, irritability, meningism, or unsteady gait 1
- Some patients with pure motor variant and AMAN subtype may have normal or exaggerated reflexes 1
Clinical Variants
- Pure motor variant: Weakness without sensory signs 1, 4
- Miller Fisher syndrome: Ophthalmoplegia, areflexia, and ataxia 1, 4
- Pharyngeal-cervical-brachial weakness: Weakness limited to cranial nerves and upper limbs 1
- Paraparetic variant: Weakness limited to lower limbs 1
- Bilateral facial palsy with paresthesias: Weakness limited to cranial nerves 1
- Other variants include pure sensory ataxia, Bickerstaff brainstem encephalitis, and pure sensory variant 1
Etiology and Pathophysiology
Infectious Triggers
- About two-thirds of patients report symptoms of infection in the 6 weeks preceding GBS onset 1, 2
- Six pathogens have been temporally associated with GBS in case-control studies:
- Absence of antecedent illness does not exclude GBS diagnosis, as infections may be subclinical 1
Immunological Mechanism
- GBS is considered an autoimmune disease triggered by preceding bacterial or viral infection 5
- Molecular mimicry plays a key role: infecting organisms share homologous epitopes with peripheral nerve components 5, 6
- In AMAN form, immune responses cross-react with gangliosides (GM1, GM1b, GD1a, GalNAc-GD1a) on motor axolemma 5
- In AIDP form, immune reactions target epitopes in Schwann cells or myelin, though exact target molecules remain unidentified 5
- Complement activation, macrophage infiltration, and edema are typical characteristics of affected peripheral nerves 1
Disease Course and Prognosis
- Monophasic clinical course with maximum disability typically reached within 2 weeks 1
- Treatment-related fluctuations and relapses occur in a minority of patients (2-5%) 1, 3
- Respiratory failure develops in about 20% of patients 1
- Mortality is estimated at 3-10% even with best medical care 1
- 60-80% of patients can walk independently 6 months after disease onset 1
- Recovery can continue for more than 3 years after onset 3
Diagnostic Considerations
- If maximum disability is reached within 24 hours or after 4 weeks, alternative diagnoses should be considered 1
- Cerebrospinal fluid typically shows albumino-cytological dissociation (elevated protein with normal cell count) 2, 6
- Electrodiagnostic studies can distinguish between subtypes: AIDP, AMAN, and AMSAN 1, 2
- Consider changing diagnosis to acute-onset chronic inflammatory demyelinating polyneuropathy if progression continues after 8 weeks 7