Write a short note on Guillain-Barré syndrome.

Definition

Guillain–Barré syndrome (GBS) is an acute, immune-mediated, inflammatory polyradiculoneuropathy characterised by rapidly progressive, symmetrical, ascending flaccid weakness with areflexia, reaching maximum severity within 4 weeks. It is the commonest cause of acute flaccid paralysis worldwide since the control of poliomyelitis.

Pathogenesis

Molecular mimicry: antibodies raised against microbial epitopes cross-react with gangliosides on peripheral nerve myelin and axolemma, causing complement-mediated demyelination or axonal injury.

Antecedent infection in about two-thirds, 1–3 weeks before onset:

• *Campylobacter jejuni* — the commonest, associated with preceding diarrhoea and with the axonal (AMAN) variant and a worse prognosis
• Cytomegalovirus, Epstein–Barr virus, *Mycoplasma pneumoniae*, HIV, hepatitis E
• Zika and dengue virus — relevant in India
• Rarely following vaccination or surgery

Variants

Clinical Features

• Progressive, symmetrical, ASCENDING weakness beginning in the legs and moving proximally, over days to a maximum by 2–4 weeks. Weakness is usually greater proximally than distally.
• Areflexia or hyporeflexia — an essential feature. Its absence should prompt reconsideration of the diagnosis.
• Sensory symptoms — paraesthesiae and neuropathic pain (often severe and under-treated) are common, but objective sensory signs are mild.
• Back and limb pain is frequent and may dominate early, delaying diagnosis.
• Cranial nerve involvement in about half — bilateral facial weakness is characteristic; bulbar weakness causes dysphagia and aspiration risk.
• Respiratory muscle weakness in 25–30%, requiring ventilation — the principal cause of death.
• Autonomic dysfunction in up to two-thirds — labile blood pressure, arrhythmias, sinus tachycardia, bradycardia and asystole (especially on tracheal suction), ileus, urinary retention, and abnormal sweating.
• Sphincter function is usually preserved early — its early loss suggests a spinal cord lesion instead.

Investigations

• CSF: "albuminocytological dissociation" — raised protein with a normal cell count. Note that this is often normal in the first week and becomes abnormal by the second — a normal early CSF does not exclude GBS. A raised cell count should prompt a search for HIV, Lyme disease, or malignant infiltration.
• Nerve conduction studies — the most useful confirmatory test: prolonged distal latencies, conduction block, temporal dispersion, absent or prolonged F-waves (early), and slowed conduction velocity in demyelinating forms; reduced amplitudes in axonal forms.
• Serial forced vital capacity and single-breath count — the most important monitoring investigation.
• Antiganglioside antibodies — anti-GM1 (AMAN), anti-GQ1b (Miller–Fisher).
• Stool culture and serology for *Campylobacter*; HIV testing in every patient; electrolytes (hyponatraemia from SIADH is common), ECG for arrhythmia.
• MRI spine with contrast where the diagnosis is uncertain — shows nerve root enhancement, and excludes cord compression, the critical differential.

Management

1. Monitoring and supportive care — where lives are saved

• Serial FVC (and single-breath count at the bedside). Elective intubation on a declining trend, before exhaustion — do not wait for hypoxia or a rising CO2, which are terminal events.
• Continuous cardiac monitoring for autonomic arrhythmia; caution with tracheal suction, which can precipitate bradycardia and asystole; treat labile blood pressure conservatively with short-acting agents.
• DVT prophylaxis (high risk from immobility), pressure area care, physiotherapy to prevent contractures, bladder and bowel care, and early nutritional support.
• Neuropathic pain management — gabapentin, pregabalin, amitriptyline; pain is frequently severe and inadequately treated.
• Psychological support — patients are often fully alert while progressively paralysed and ventilated, which is profoundly frightening.

2. Disease-modifying treatment

• Intravenous immunoglobulin or plasma exchange — equally effective; IVIG is usually preferred for ease of administration and availability. Give to patients who are unable to walk unaided, or who are deteriorating rapidly, and within the first 2 weeks of onset for maximal benefit.
• Combining the two confers no additional benefit.
• CORTICOSTEROIDS ARE NOT EFFECTIVE and should not be used — a favourite examination point, and a genuine clinical error.

3. Rehabilitation — prolonged multidisciplinary rehabilitation is required; recovery follows the reverse order of onset and may take months.

Prognosis

About 80% walk independently at 6 months and 60% recover full strength at 1 year; mortality is 3–10%, from respiratory failure, autonomic arrhythmia, pulmonary embolism and sepsis. Poor prognostic factors: older age, rapid onset, need for ventilation, preceding diarrhoeal (Campylobacter) illness, axonal variant, and low distal motor amplitudes on nerve conduction studies. Around 5–10% relapse or evolve into CIDP (chronic inflammatory demyelinating polyneuropathy) if progression continues beyond 8 weeks.