Peripheral Neuropathies: CMT & Guillain-Barré for MRCP Part 1

Crack Medicine
4 days ago
4 min read

TL;DR

Peripheral Neuropathies: CMT & Guillain-Barré are frequently tested neurology topics in MRCP Part 1 because they illustrate contrasting patterns of chronic inherited neuropathy and acute immune-mediated neuropathy. Charcot-Marie-Tooth disease presents with slowly progressive distal weakness and characteristic foot deformities, while Guillain-Barré syndrome causes rapidly progressive ascending paralysis with areflexia and characteristic cerebrospinal fluid findings. Candidates must recognise key clinical patterns, nerve conduction findings, and emergency complications such as respiratory failure.

Why this matters in MRCP Part 1

Peripheral neuropathy questions typically assess a candidate’s ability to recognise patterns of weakness and disease time course.

MRCP questions often focus on:

Acute vs chronic neuropathy
Reflex changes
Sensory patterns
Nerve conduction study interpretation
Cerebrospinal fluid findings
Complications such as respiratory failure

Because Guillain-Barré syndrome may cause rapid neurological deterioration, recognising it is clinically important as well as exam-relevant.

Core Concepts Candidates Must Know

1. Charcot-Marie-Tooth Disease (CMT)

Charcot-Marie-Tooth disease represents the most common inherited peripheral neuropathy, affecting approximately 1 in 2,500 individuals.

It is usually caused by genetic mutations affecting myelin or axonal structure, most commonly duplication of the PMP22 gene.

Typical clinical features include:

Slowly progressive distal weakness
Distal muscle wasting
Foot deformities such as pes cavus
Reduced or absent tendon reflexes
Sensory loss in a stocking-glove distribution

Patients often develop the classic appearance of “inverted champagne bottle” legs due to distal muscle wasting.

Nerve conduction studies typically show markedly slowed conduction velocities, reflecting demyelination.

Further clinical information is summarised by the NHS overview of Charcot-Marie-Tooth disease:https://www.nhs.uk/conditions/charcot-marie-tooth-disease/

2. Guillain-Barré Syndrome (GBS)

Guillain-Barré syndrome is an acute inflammatory demyelinating polyneuropathy (AIDP) caused by autoimmune attack on peripheral nerves.

It commonly develops 1–4 weeks after infection.

Common preceding infections include:

Campylobacter jejuni
Cytomegalovirus
Epstein–Barr virus
Influenza

Typical clinical features:

Rapidly progressive ascending weakness
Areflexia
Mild sensory symptoms
Cranial nerve involvement (especially facial palsy)
Autonomic dysfunction

Respiratory muscle involvement can lead to respiratory failure, requiring mechanical ventilation in severe cases.

A clinical overview from NICE and NHS guidance is available here:https://www.nhs.uk/conditions/guillain-barre-syndrome/

3. Cerebrospinal Fluid Findings

A classic diagnostic clue in Guillain-Barré syndrome is albuminocytological dissociation.

This refers to:

Elevated CSF protein
Normal white blood cell count

This occurs because inflammation affects nerve roots without causing significant cellular infiltration.

CSF protein levels usually rise after the first week of symptoms, so early lumbar puncture may be normal.

4. Nerve Conduction Studies

Electrophysiology plays an important role in distinguishing neuropathies.

Typical findings include:

Demyelinating neuropathy

Reduced conduction velocity
Conduction block
Prolonged distal latency

Axonal neuropathy

Reduced amplitude
Relatively preserved conduction velocity

Both CMT and Guillain-Barré syndrome commonly produce demyelinating patterns.

5. Key Differences Between CMT and GBS

Feature	Charcot-Marie-Tooth Disease	Guillain-Barré Syndrome
Onset	Chronic	Acute
Cause	Genetic	Immune-mediated
Progression	Slowly progressive	Rapid (days–weeks)
Reflexes	Reduced	Absent
Sensory symptoms	Mild	Mild–moderate
CSF findings	Normal	Albuminocytological dissociation
Treatment	Supportive	IVIG or plasma exchange

MRCP questions often rely heavily on time course and clinical history to differentiate these conditions.

Five Most Tested Subtopics in MRCP

Ascending paralysis in Guillain-Barré syndrome
Albuminocytological dissociation in CSF
Campylobacter infection preceding GBS
Pes cavus and distal wasting in CMT
IVIG or plasma exchange as treatment for GBS

These are recurring exam themes and frequently appear in clinical vignettes.

To practise similar cases, attempt a Start a mock test.

Practical Mini-Case (MRCP-style)

A 42-year-old man presents with progressive weakness in both legs over five days. The weakness began in the feet and has now spread to the thighs. Examination shows absent knee and ankle reflexes. Cranial nerve examination reveals mild bilateral facial weakness.

Lumbar puncture shows elevated CSF protein with normal cell count.

What is the most likely diagnosis?

A. Multiple sclerosisB. Myasthenia gravisC. Guillain-Barré syndromeD. Charcot-Marie-Tooth disease

Answer: C. Guillain-Barré syndrome

Explanation

The key clues are:

Ascending paralysis
Areflexia
Recent rapid progression
Albuminocytological dissociation

These features strongly indicate Guillain-Barré syndrome, an acute immune-mediated demyelinating neuropathy.

Study-Tip Checklist for MRCP Part 1

When revising peripheral neuropathies, ensure you can quickly identify the following:

✔ Acute vs chronic neuropathy patterns✔ Ascending paralysis in Guillain-Barré syndrome✔ Albuminocytological dissociation in CSF✔ Characteristic foot deformities in CMT✔ Differences between demyelinating and axonal neuropathy

A practical strategy is to combine theory with question practice using the Free MRCP MCQs.

For broader neurology preparation, see the related guide Neurology revision for MRCP Part 1:https://www.crackmedicine.co.uk/blog/neurology-revision-mrcp/

Common Pitfalls in MRCP Questions

Confusing Guillain-Barré syndrome with myasthenia gravis
Forgetting that steroids are ineffective in GBS
Missing autonomic dysfunction in GBS cases
Ignoring pes cavus as a clue to inherited neuropathy
Assuming all neuropathies present with sensory loss

Avoiding these traps can significantly improve exam accuracy.

Young doctor studying with laptop and medical books at a desk.

FAQs (People Also Ask)

What infection commonly precedes Guillain-Barré syndrome?

The most common trigger is Campylobacter jejuni gastroenteritis. Molecular mimicry between bacterial antigens and nerve gangliosides leads to immune-mediated nerve damage.

What is albuminocytological dissociation?

It refers to high protein but normal white cell count in cerebrospinal fluid, a hallmark diagnostic feature of Guillain-Barré syndrome.

What are classic signs of Charcot-Marie-Tooth disease?

Patients typically present with distal muscle wasting, pes cavus, reduced reflexes, and slowly progressive weakness beginning in adolescence or early adulthood.

How is Guillain-Barré syndrome treated?

The two main treatments are intravenous immunoglobulin (IVIG) and plasma exchange. Early treatment reduces complications and speeds recovery.

Why is Guillain-Barré syndrome a neurological emergency?

Because rapid progression may lead to respiratory failure or severe autonomic instability, requiring close monitoring and sometimes intensive care.

Ready to start?

Preparing for MRCP Part 1 requires mastering high-yield neurology topics such as Peripheral Neuropathies: CMT & Guillain-Barré through consistent revision and exam-style practice. Strengthen your preparation with structured learning resources, expert-led lectures, and clinically focused question banks available at Crack Medicine.

Start your preparation here:👉 https://www.crackmedicine.co.uk

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