Lucan · Conditions

Guillain-Barré syndrome

Australian guidance: eTG Neurology + Australasian neurology consensus

1. Definition and epidemiology

Guillain-Barré syndrome (GBS) is an acute immune-mediated polyradiculoneuropathy characterised by progressive, predominantly ascending limb weakness and areflexia, typically reaching nadir within four weeks. In Australia, the annual incidence is approximately 1 to 2 cases per 100,000 population, consistent with international figures; it remains the most common cause of acute flaccid paralysis in adults following the near-elimination of poliomyelitis. Males are affected slightly more often than females, and incidence increases with age, though GBS affects all age groups including children.

2. Pathophysiology

Per Robbins Ch 27 Peripheral Nerves, GBS results from aberrant molecular mimicry triggered by a preceding infection, most commonly Campylobacter jejuni enteritis (accounting for roughly 30 to 40% of cases), though cytomegalovirus, Epstein-Barr virus, Mycoplasma pneumoniae, and influenza A are also recognised antecedents. In the acute inflammatory demyelinating polyradiculoneuropathy (AIDP) subtype, dominant in Australia and Western countries, T-cell-mediated and antibody-mediated attack targets peripheral nerve myelin, particularly at the nodes of Ranvier and the paranodal regions. Complement activation and macrophage infiltration strip the myelin sheath, causing segmental demyelination with relative axonal preservation in early or mild disease. The acute motor axonal neuropathy (AMAN) subtype, more common in Asia, involves IgG autoantibodies directed against gangliosides GM1, GD1a, and GalNAc-GD1a on the axolemma, causing primary axonal injury without demyelination and typically a more severe course. Anti-GQ1b antibodies are present in more than 90% of cases of Miller Fisher syndrome, the triad of ophthalmoplegia, ataxia, and areflexia that is now classified within the GBS spectrum.

3. Clinical presentation and diagnostic criteria

A symmetrical ascending limb weakness beginning in the legs is the cardinal feature, typically preceded by a respiratory or gastrointestinal illness one to four weeks earlier. Weakness progresses over days and may ascend to involve the arms, facial muscles, and bulbar musculature. Areflexia or profound hyporeflexia in affected limbs is a hallmark and should raise suspicion when present even before weakness is maximal. Autonomic dysfunction occurs in up to 70% of patients and manifests as cardiac arrhythmias, labile blood pressure, urinary retention, or ileus; autonomic instability is an independent predictor of ICU admission. Respiratory muscle involvement requiring mechanical ventilation occurs in approximately 25 to 30% of patients, making serial forced vital capacity (FVC) measurement critical. Diagnostic criteria (Brighton Collaboration levels 1 to 3) require bilateral limb weakness and reduced or absent deep tendon reflexes in weak limbs; cerebrospinal fluid (CSF) showing cytoalbuminous dissociation supports the diagnosis, as does electrodiagnostic evidence of polyneuropathy. The Brighton criteria provide a standardised framework used in post-vaccine surveillance in Australia.

4. Investigations and AU-specific cutoffs

Investigations are sequenced to confirm the diagnosis, assess respiratory risk, and exclude mimics.

1. Lumbar puncture and CSF analysis: The classic cytoalbuminous dissociation shows elevated protein (typically above 0.45 g/L, often 1 to 3 g/L) with fewer than 10 white cells per microlitre. CSF may be normal in the first week of illness; a normal early CSF does not exclude GBS.
2. Nerve conduction studies and electromyography (NCS/EMG): The gold standard for subtype classification. AIDP shows prolonged distal latencies, reduced conduction velocity, conduction block, and dispersed compound motor action potentials (CMAPs). AMAN and AMSAN subtypes show reduced CMAP amplitudes with relatively preserved conduction velocity. Studies should be performed by an experienced neurophysiologist and may need to be repeated if initially equivocal.
3. Respiratory function: FVC measured at least twice daily in hospitalised patients. FVC below 20 mL/kg, maximal inspiratory pressure below 30 cmH2O, or maximal expiratory pressure below 40 cmH2O (the "20-30-40 rule") are thresholds prompting urgent anaesthetic or intensive care review for elective intubation, as emergency intubation in GBS is associated with significant morbidity. Pulse oximetry alone is an unreliable guide because patients may desaturate late.
4. Anti-ganglioside antibodies: Anti-GQ1b serology is indicated when Miller Fisher syndrome or Bickerstaff encephalitis is suspected. Anti-GM1 and anti-GD1a are associated with AMAN and may predict a more severe axonal course. Routine panel testing is not mandated in all patients but assists with prognostication.
5. Stool PCR for Campylobacter jejuni: Indicated when diarrhoeal prodrome is reported, to guide infection control and epidemiological recording; antibiotic treatment of the preceding infection does not alter the GBS course once it has begun.
6. Bloods: Full blood count, electrolytes, renal function, liver function, and hepatitis B serology before intravenous immunoglobulin (IVIg). Serum sodium should be monitored given the risk of syndrome of inappropriate antidiuretic hormone secretion.
7. MRI spine: Indicated to exclude compressive myelopathy where spinal cord disease cannot be clinically excluded, particularly in patients with bladder or bowel involvement disproportionate to limb weakness.

5. Management

All patients with confirmed or strongly suspected GBS should be admitted to hospital, given the unpredictability of respiratory and autonomic deterioration. Patients with rapid progression, bulbar involvement, autonomic dysfunction, or FVC below 60% of predicted should be admitted to a facility with ICU access and monitored accordingly.

Specific immunotherapy must be initiated as soon as feasible once the diagnosis is established, regardless of disease severity at presentation, because early treatment reduces time to unaided walking and shortens the duration of mechanical ventilation. The two treatments with equivalent efficacy are:

• Intravenous immunoglobulin (IVIg): 0.4 g/kg/day for five days (total 2 g/kg). This is the preferred first-line treatment in Australia per eTG Neurology, partly because of greater logistical ease than plasmapheresis. IVIg is approved by the Australian Commission on Safety and Quality in Health Care (ACSQHC) Criteria for the Clinical Use of Intravenous Immunoglobulin in Australia for GBS as a Category 1 (critical) indication, removing the need for individual authority. Pre-treatment hepatitis B serology is mandatory because IVIg can trigger HBV reactivation.
• Therapeutic plasma exchange (plasmapheresis): Four to six exchanges over one to two weeks, removing one plasma volume per exchange. Of equivalent efficacy to IVIg when commenced within four weeks of onset. Preferred in centres with established apheresis capability or when IVIg is contraindicated (e.g. IgA deficiency with anti-IgA antibodies, severe renal failure, or uncontrolled hypertension). Combination of IVIg followed by plasmapheresis, or sequential cycles, confers no additional benefit.

Corticosteroids are not recommended and have been shown in randomised trials to confer no benefit and potentially a modest harmful effect on time to recovery.

Supportive care is critical. DVT prophylaxis with low-molecular-weight heparin should be commenced on admission in non-ambulant patients, with mechanical sequential compression devices as an adjunct. Pain (often neuropathic, burning, or radicular in character) is undertreated in GBS; gabapentin or pregabalin are recommended first-line agents, with opioids reserved for inadequate control. Bladder care requires monitoring for urinary retention; bowel care requires a prophylactic regimen to prevent constipation and ileus from autonomic dysfunction. Early involvement of physiotherapy, occupational therapy, and speech pathology is essential given prolonged recovery trajectories.

6. Pharmacology and AU PBS notes

IVIg (Privigen, Intragam P, Hizentra, Gamunex, Kiovig): Human normal immunoglobulin preparations for IV use. In Australia, IVIg for GBS is funded through the National Blood Authority (NBA) BloodSTAR system under the Category 1 critical indication; prescribers must register and submit the request through BloodSTAR prior to dispensing. The standard PBS or hospital formulary route does not apply; supply is via the NBA. No streamlined PBS code exists because supply is through a separate national blood products framework.

Gabapentin (Neurontin, generic): 100 to 300 mg three times daily, titrated to effect; evidence specifically in GBS neuropathic pain is limited but supported by expert consensus. Listed on PBS for neuropathic pain (Streamlined Authority code 1323 for peripheral neuropathy).

Pregabalin (Lyrica, generic): 25 to 75 mg twice daily, titrated; PBS Streamlined Authority code 10716 for peripheral neuropathic pain. Prefer in patients with renal impairment due to more predictable pharmacokinetics than gabapentin.

Low-molecular-weight heparin: Enoxaparin 40 mg subcutaneous once daily for DVT prophylaxis; dose-adjust for renal impairment. PBS listed for VTE prophylaxis in medical patients.

7. Complications and monitoring

Respiratory failure is the most immediately life-threatening complication. Serial FVC monitoring twice daily (or more frequently with rapid progression) is mandatory in all hospitalised patients. Elective intubation using a rapid sequence technique is preferred over emergency intubation when FVC crosses the 20 mL/kg threshold or when dysphagia impairs safe airway protection. Prolonged mechanical ventilation is anticipated in severe cases; tracheostomy should be considered early in patients with bulbar dysfunction unlikely to resolve within two weeks.

Autonomic instability: Cardiac monitoring should be continuous throughout the acute phase. Hypertensive crises and severe bradyarrhythmias may require short-acting agents; vasodilatory agents should be used with caution given the labile blood pressure characteristic of GBS autonomic dysfunction. Severe bradycardia or asystole may occur spontaneously and the threshold for temporary pacing should be low.

Treatment-related fluctuations: Approximately 5 to 10% of patients deteriorate after initial improvement post-IVIg (treatment-related fluctuations), which is distinct from a relapse and does not necessarily warrant a second treatment course. True relapse (recurrence after full recovery) occurs in approximately 2 to 5% and defines chronic inflammatory demyelinating polyneuropathy (CIDP) if clinical criteria are met.

Recovery and prognosis: The EGOS (Erasmus GBS Outcome Score) and mEGOS (modified EGOS) are validated prognostic tools incorporating age, preceding diarrhoeal illness, and disability at two weeks. Approximately 80% of patients with AIDP regain independent ambulation by six months, though fatigue, neuropathic pain, and residual sensory disturbance are common long-term sequelae. Axonal subtypes (AMAN, AMSAN) carry greater risk of incomplete recovery.

Monitoring schedule: Twice-daily FVC, continuous cardiac monitoring, and daily autonomic observations during the acute phase; reassess IgG trough level and renal function five to seven days after IVIg; weekly NCS/EMG is not routinely required unless diagnosis is uncertain; outpatient neurological review at six weeks, three months, and six months to assess recovery trajectory and identify evolving CIDP.

Written for Australian practice and grounded in the guidance named above. Study material only — not medical advice. Always check against current guidelines.