Erfan Bashar
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Neuropathies — Guillain-Barre Syndrome

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Educational scope notice: This is a study note for medical students, not medical advice, diagnosis, or treatment guidance. Clinical management should follow local protocols and current guidelines.

Guillain-Barre syndrome (GBS) is an acute immune-mediated polyradiculoneuropathy, attacking nerve roots and peripheral nerves together. It is a neurological emergency because ascending weakness can reach respiratory muscles. Roughly a quarter of patients develop respiratory failure, so suspected cases are monitored as inpatients from the start.

Clinical pattern

The classic course begins with tingling in the feet that spreads to the hands, followed by relatively symmetric weakness rising from the legs through the trunk and arms, sometimes to facial, bulbar, and respiratory muscles. Absent deep tendon reflexes, or distal absence with proximal reduction, is characteristic. Sensory loss is usually mild and distal. Autonomic instability with tachycardia, blood pressure swings, arrhythmias, or urinary retention is common, as are cranial nerve signs including facial palsy and swallowing difficulty.

The early examination can be normal and the first presentation misattributed, so the functional history matters: what the patient can no longer do that they could do days ago. Onset over hours to days with areflexia should prompt admission regardless of whether the final diagnosis proves to be GBS or a mimic such as myasthenia gravis.

The Miller Fisher variant presents differently, with the triad of ophthalmoplegia, ataxia, and areflexia, and associates with anti-GQ1b antibodies.

Demyelinating versus axonal disease

GBS spans two poles. Acute inflammatory demyelinating polyradiculoneuropathy (AIDP), the most common form in Western countries, attacks myelin while axons survive, slows conduction, and generally recovers better because remyelination is possible. Acute motor axonal neuropathy (AMAN) and its motor-sensory counterpart (AMSAN) attack axons directly through the node of Ranvier, reduce amplitudes with relatively preserved velocity in surviving fibres, and carry a worse prognosis. Axons regrow at roughly 1 mm per day and may never fully recover. Distinguishing the two is a prognostic exercise, not an admission-delaying one.

Post-infectious mechanism

Most cases follow an infection by 1 to 4 weeks, through molecular mimicry: antibodies raised against the microbe cross-react with nerve antigens that share molecular structure. The established link is Campylobacter jejuni, whose surface lipo-oligosaccharides contain GM1-like epitopes also present on human nerve membranes, so anti-GM1 antibodies injure both. Cytomegalovirus, Epstein-Barr virus, Mycoplasma pneumoniae, and Zika virus are other recognized triggers. Respiratory infections predominate as triggers in Europe and gastrointestinal ones in tropical regions, while overall prevalence stays similar, suggesting a host-susceptibility component.

Vaccination carries a very small excess risk, concentrated in the weeks after immunization, but the far larger risk comes from the infections themselves, so the benefit-risk balance favors vaccination.

Tempo and prognosis

Progression typically peaks within 4 weeks, most often within 2, and recovery begins 2 to 4 weeks after progression stops. Demyelinating disease recovers better; axonal disease leaves more residual disability. With modern immunotherapy most patients regain independence, while roughly 1 to 2 in 10 carry lasting deficits. Before immunotherapy existed, about half became bed-bound and mortality reached the low teens, which is why early treatment dominates outcomes.

Diagnosis

Diagnosis is primarily clinical: acute progressive symmetric weakness with areflexia after a recent infection. Investigations support rather than replace judgment.

Spinal fluid shows albuminocytological dissociation, raised protein with a normal cell count, reflecting inflamed roots leaking protein across the blood-nerve barrier. Protein may still be normal in the first days and rises over the first week, so early normal fluid never excludes the disease. Nerve conduction studies are often normal in the first days and diagnostic in most patients by the second week. Anti-ganglioside antibodies may be present but are frequently absent, and their absence changes nothing.

Differentials include poliomyelitis (now historical in most settings, with febrile asymmetric paralysis and spinal fluid pleocytosis), myasthenia gravis (fatigable weakness without sensory loss), acute myelitis, spinal cord compression from metastasis, vasculitic neuropathy (asymmetric and stepwise), and thiamine deficiency.

Treatment

Treatment starts as early as possible to halt the immune attack before further destruction.

IV immunoglobulin is usually preferred first because it can begin in the emergency department without special equipment or hemodynamic shifts. The standard total dose is 2 g per kg over 4 to 5 days. Plasma exchange, which removes pathogenic antibodies directly, hastens recovery to an equivalent degree, so the choice follows availability, comorbidity, and blood pressure stability. Giving IV immunoglobulin after plasma exchange adds no benefit. A second immunoglobulin course for simple non-response has shown no additional advantage and raises thrombosis risk. Treatment escalation is reserved for genuine worsening after initial improvement, where plasma exchange is the usual switch.

Corticosteroids are not effective in GBS, even combined with immunotherapy, which separates it sharply from CIDP, where steroids work.

Supportive care decides survival: regular vital-capacity measurement with ICU transfer for respiratory decline, autonomic monitoring, thromboembolism prophylaxis with early physiotherapy, pain control stepping from anti-inflammatories through anti-epileptics to opioids, and antibiotics for intercurrent pneumonia or urinary infection. Complications during admission include arrhythmias, blood pressure instability, thromboembolism, and nosocomial infection, which is why close inpatient monitoring is mandatory rather than optional.

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