Medicine – Guillain–Barré Syndrome (Acute Inflammatory Demyelinating Polyneuropathy)

Guillain–Barré syndrome (GBS) is an acute immune-mediated polyradiculoneuropathy that typically causes rapidly progressive, symmetrical weakness with reduced or absent reflexes. The most common form in many regions is acute inflammatory demyelinating polyneuropathy (AIDP), although other axonal variants also exist.

It is often triggered by a recent infection, but the neurological illness itself is not usually due to direct infection of the nerves. Instead, it results from an abnormal immune response directed against components of the peripheral nervous system.

1. Basic Mechanism

GBS is best regarded as an autoimmune inflammatory neuropathy rather than simply an “acute infective polyneuropathy.”

A preceding infection may stimulate the immune system to produce antibodies that cross-react with peripheral nerve components through a process known as molecular mimicry.

This immune response can damage:

Peripheral nerve myelin.

Nerve roots.

Axons in some variants.

2. Peripheral Rather Than Central Nervous System Disease

The original note refers to antibodies against central or peripheral nerve proteins, but classic GBS is fundamentally a disease of the peripheral nervous system.

The affected structures include:

Peripheral motor nerves.

Sensory nerves.

Spinal nerve roots.

Cranial nerves.

The brain and spinal cord themselves are not the primary sites of injury.

3. AIDP

Acute inflammatory demyelinating polyneuropathy is the classic demyelinating form of GBS.

Immune-mediated injury damages the myelin surrounding peripheral nerves.

This causes:

Slowing of nerve conduction.

Conduction block.

Temporal dispersion.

The result is progressive weakness and loss of reflexes.

4. Axonal Variants

Not all GBS is demyelinating.

Important variants include:

Acute motor axonal neuropathy, AMAN.

Acute motor and sensory axonal neuropathy, AMSAN.

These forms involve axonal injury rather than primarily myelin damage.

Therefore:

GBS is the overall syndrome; AIDP is one important subtype.

5. Ascending Symmetrical Weakness

The classic presentation is rapidly progressive symmetrical weakness beginning in the legs and ascending upward.

Patients may initially notice:

Difficulty climbing stairs.

Difficulty standing from a chair.

Leg heaviness.

Unsteady walking.

The weakness may then spread to:

Thighs.

Trunk.

Upper limbs.

Bulbar and respiratory muscles.

6. Paralysis

In severe disease, weakness can progress to flaccid paralysis.

Because the disorder can worsen over hours or days, patients require close monitoring even if weakness initially appears mild.

Some patients may lose the ability to:

Walk.

Stand.

Lift the arms.

Swallow effectively.

Breathe independently.

7. Hyporeflexia and Areflexia

One of the most characteristic examination findings is:

Reduced or absent deep tendon reflexes.

The ankle jerks are often lost early.

Reflex abnormalities occur because peripheral nerve and nerve-root conduction is impaired.

Therefore, the classic combination is:

Progressive symmetrical weakness + hyporeflexia/areflexia.

8. Sensory Symptoms

Patients often report:

Paraesthesiae.

Tingling.

Pins and needles.

Numbness.

These sensory symptoms may begin in the feet and hands.

However, objective sensory loss is often relatively mild compared with the degree of motor weakness.

9. Pain

Pain is common and may be under-recognised.

Patients can develop:

Back pain.

Radicular pain.

Deep aching muscular pain.

Neuropathic burning pain.

Pain can sometimes precede obvious weakness.

10. Cranial Nerve Involvement

Cranial nerve involvement is common.

The facial nerves are particularly frequently affected, and weakness may be bilateral.

Patients may develop:

Facial weakness.

Difficulty closing the eyes.

Bulbar weakness.

Dysphagia.

Dysarthria.

The traditional figure of around half of patients developing some cranial nerve involvement is a reasonable teaching approximation, although the exact frequency varies between series and GBS subtypes.

11. Bulbar Weakness

Involvement of the lower cranial nerves can impair swallowing and airway protection.

Patients may develop:

Weak voice.

Dysarthria.

Dysphagia.

Choking.

Aspiration risk.

Bulbar weakness also increases concern for impending respiratory deterioration.

12. Respiratory Muscle Weakness

Respiratory involvement is one of the most dangerous complications of GBS.

Weakness may affect:

Diaphragm.

Intercostal muscles.

Accessory respiratory muscles.

A patient can deteriorate quickly and may require mechanical ventilation.

Importantly, respiratory muscle weakness may progress before severe abnormalities appear on routine oxygen saturation.

13. Autonomic Dysfunction

GBS can affect autonomic nerve fibres and produce potentially dangerous cardiovascular instability.

Manifestations include:

Tachycardia.

Bradycardia.

Marked fluctuations in blood pressure.

Cardiac arrhythmias.

Urinary retention.

Ileus.

Abnormal sweating.

Because severe autonomic instability can cause sudden complications, monitoring is essential.

14. Preceding Infection

A large proportion of patients report an infection in the preceding days or weeks.

The most strongly established infectious trigger is:

Campylobacter jejuni.

Other recognised triggers include:

Cytomegalovirus.

Epstein–Barr virus.

Mycoplasma pneumoniae.

Influenza and other respiratory infections.

Other viral infections can also precede GBS.

15. Campylobacter jejuni

Campylobacter jejuni is one of the most important associations.

It commonly causes a diarrhoeal illness before the neurological symptoms begin.

Certain bacterial surface structures resemble peripheral nerve gangliosides, leading to molecular mimicry and production of cross-reactive antibodies.

This association is particularly strong with some axonal variants of GBS.

16. Time Course

GBS is an acute disorder.

Weakness usually progresses over:

Hours to days, and up to several weeks.

By definition, progression to the worst point generally occurs within 4 weeks.

If weakness continues to progress for substantially longer, alternative diagnoses such as chronic inflammatory demyelinating polyneuropathy should be considered.

17. CSF Findings

Lumbar puncture classically demonstrates:

Raised CSF protein with a normal or only mildly increased white cell count.

This is called:

Albuminocytologic dissociation.

It reflects increased protein from inflamed nerve roots without a major inflammatory cellular response in the CSF.

18. Albuminocytologic Dissociation

The characteristic pattern is:

High protein + few or no white cells.

This finding strongly supports GBS in the appropriate clinical context.

However, CSF protein may still be normal early in the illness, particularly during the first several days.

Therefore:

A normal early lumbar puncture does not exclude GBS.

19. CSF White Cell Count

A substantially increased CSF white cell count is not typical.

If there is marked pleocytosis, clinicians should consider alternative diagnoses such as:

Infectious polyradiculitis.

HIV-related disease.

Lyme disease.

Other inflammatory or infectious conditions.

20. Nerve Conduction Studies

Nerve conduction studies and EMG help confirm peripheral nerve involvement.

In AIDP, nerve conduction studies may show:

Slowed conduction velocity.

Prolonged distal motor latencies.

Prolonged or absent F waves.

Conduction block.

Temporal dispersion.

These findings support a demyelinating neuropathy.

21. Axonal Study Patterns

In AMAN or AMSAN, conduction studies may instead show evidence of axonal loss.

Therefore, not every patient with GBS will show the same classic demyelinating pattern.

This is another reason why GBS should not be equated completely with AIDP.

22. Autoantibodies

Certain antiganglioside antibodies may be detectable.

Examples include:

Anti-GM1 antibodies.

Anti-GD1a antibodies.

Anti-GQ1b antibodies.

However, routine antibody testing is not required to diagnose typical GBS.

The clinical pattern, CSF findings, and neurophysiology are usually more important.

23. Anti-GQ1b Antibodies

Anti-GQ1b antibodies are strongly associated with Miller Fisher syndrome, a GBS variant.

Miller Fisher syndrome classically presents with:

Ophthalmoplegia.

Ataxia.

Areflexia.

This is a useful high-yield association.

24. Respiratory Monitoring

Because deterioration can occur quickly, respiratory function must be monitored closely.

A commonly used bedside measurement is:

Forced vital capacity, FVC.

Serial measurements are more useful than a single value because the trend shows whether respiratory muscle weakness is progressing.

25. Frequency of FVC Monitoring

The original note recommends 4-hourly FVC, which reflects the need for close observation in patients at risk.

The exact frequency depends on:

Severity of weakness.

Rate of progression.

Bulbar involvement.

Current respiratory measurements.

Patients with rapidly worsening disease may need even more frequent respiratory assessment in a high-dependency or intensive care setting.

26. Features Suggesting Impending Ventilatory Failure

Warning signs include:

Rapidly declining FVC.

Weak cough.

Difficulty counting in one breath.

Bulbar weakness.

Use of accessory respiratory muscles.

Orthopnoea.

Inability to clear secretions.

Rapid progression of limb weakness.

These findings should prompt urgent critical-care assessment.

27. Intravenous Immunoglobulin

Intravenous immunoglobulin, IVIG, is one of the main disease-modifying treatments.

It modifies the pathological immune response and can shorten recovery when given appropriately.

A standard course is usually delivered over several days.

28. Plasma Exchange

Plasma exchange, or plasmapheresis, is also effective.

It removes circulating pathogenic antibodies and other immune factors.

Both:

IVIG

and

Plasma exchange

are accepted effective treatments.

They generally have comparable efficacy when used appropriately.

29. IVIG and Plasma Exchange Are Alternatives

These treatments are usually regarded as alternative first-line immunotherapies, rather than therapies routinely combined together.

Giving plasma exchange immediately after IVIG can remove the administered immunoglobulin and is generally not useful as a routine strategy.

30. Corticosteroids

An important examination point is:

Corticosteroids are not an effective routine treatment for GBS.

This distinguishes GBS from several other autoimmune neurological disorders.

31. Mechanical Ventilation

Patients with severe respiratory weakness may require:

Endotracheal intubation and mechanical ventilation.

Early recognition is important because emergency intubation in a patient with severe bulbar and respiratory weakness carries additional risk.

Respiratory support is therefore a major part of GBS management.

32. Supportive Care

Supportive treatment is crucial because neurological recovery may take weeks or months.

Management includes:

DVT prevention.

Pressure-area care.

Pain control.

Physiotherapy.

Nutrition.

Swallowing assessment.

Bladder and bowel management.

Cardiac and blood-pressure monitoring.

33. Rehabilitation

As nerve function recovers, patients may require prolonged rehabilitation.

This can involve:

Physiotherapy.

Occupational therapy.

Mobility aids.

Muscle strengthening after recovery begins.

Psychological support.

Fatigue may persist even after substantial motor recovery.

34. Prognosis

Most patients eventually recover substantially, but recovery can be slow.

Some patients are left with:

Residual weakness.

Neuropathic pain.

Fatigue.

Difficulty walking.

A minority develop severe permanent disability or die from complications such as respiratory failure, infection, or autonomic instability.

35. Guillain–Barré Syndrome – Note Form

Disease: acute immune-mediated polyradiculoneuropathy.

Most common classic subtype: AIDP.

Main pathology in AIDP: autoimmune demyelination of peripheral nerves and nerve roots.

Other forms: axonal variants such as AMAN and AMSAN.

Typical presentation: ascending symmetrical weakness.

Reflexes: reduced or absent.

Sensory symptoms: paraesthesiae and mild numbness.

Severe progression: flaccid paralysis.

Cranial nerves: commonly involved, especially bilateral facial weakness.

Bulbar involvement: dysphagia and aspiration risk.

Autonomic dysfunction: arrhythmias, BP instability, urinary retention and ileus.

Major infectious trigger: Campylobacter jejuni.

Other triggers: CMV, EBV, Mycoplasma and other infections.

CSF: raised protein with normal or mildly raised cells.

Term: albuminocytologic dissociation.

Nerve conduction in AIDP: slowed conduction, prolonged latencies, conduction block and prolonged/absent F waves.

Antibodies: antiganglioside antibodies may occur but are not required for routine diagnosis.

Respiratory monitoring: serial FVC and close clinical observation.

Treatment: IVIG or plasma exchange.

Respiratory failure: mechanical ventilation when required.

Steroids: not routinely effective.

36. Characteristic Examination Pattern

The classic clinical pattern is:

Ascending symmetrical weakness + areflexia/hyporeflexia + relatively mild sensory symptoms.

If severe, add:

Facial/bulbar weakness + autonomic instability + respiratory muscle weakness.

This combination should immediately raise suspicion for GBS.

Key Clinical Pattern

Think of Guillain–Barré syndrome as:

Recent infection → autoimmune peripheral nerve injury → rapidly ascending symmetrical weakness + absent reflexes.

The high-yield diagnostic pattern is:

Weakness + areflexia + CSF high protein with few cells + abnormal nerve conduction studies.

The major danger is:

Respiratory failure + autonomic instability.

The main treatments are:

IVIG OR plasma exchange + intensive supportive and respiratory care when required.

And remember:

GBS affects the peripheral nervous system, not primarily the central nervous system.