Peripheral neuropathy

Question 1

What happens when the motor part of a large nerve fibre is damaged (in terms of symptoms and effects on power, sensation and reflexes)?

Answer 1

• Symptoms - weakness, unsteadiness and wasting
• Power - reduced
• Sensation - normal
• Reflexes - absent

Question 2

What happens when the sensory part of a large nerve fibre is damaged (in terms of symptoms and effects on power, sensation and reflexes)?

Answer 2

• Symptoms - numbness, paraesthesia, unsteadiness
• Power - normal
• Sensation - vibration and JPS reduced
• Reflexes - absent

Question 3

What happens when a small nerve fibre is damaged (in terms of symptoms and effects on power, sensation and reflexes)?

Answer 3

• Symptoms - pain and dysesthesia
• Power - normal
• Sensation - pin prick and temperature reduced
• Reflexes - present

Question 4

What happens when autonomic fibres are damaged (in terms of symptoms and effects on power, sensation and reflexes)?

Answer 4

• Symptoms - dizziness (postural hypotension), impotence, N+V (gastroparesis)
• Power - normal
• Sensation - normal
• Reflexes - present

Question 5

What is the name given to nerve root damage?

Answer 5

Radiculopathy

Question 6

What is the name given to nerve plexus injury?

Answer 6

Plexopathy

Question 7

What is the name given to injury to a peripheral nerve?

Answer 7

Peripheral neuropathy, which encompasses; mononeuropathy and mononeuritis multiplex

Question 8

What are some causes of demyelinating neuropathy?

Answer 8

• Acute (days to weeks) - Guillaine Barre syndrome
• Chronic (months to years) - chronic inflammatory demyelinating polyradiculopathy (CIDP), hereditary sensory motor neuropathy (Charcot-Marie-Tooth disease)

Question 9

How does Guillain-Barre syndrome typically present?

Answer 9

• Progressive paraplegia over days up to 4 weeks
• Associated sensory symptoms proceed weakness
• Pain is very common!
• Peak symptoms are 10-14 days into onset of illness
• Examination can be normal in the initial phases of illness

Question 10

How is Guillain-Barre syndrome treated?

Answer 10

• Immunoglobulin infusion and/or plasma exchange
• 25% require mechanical ventilation
• 10% die mainly from autonomic failure (cardiac arrhythmia)

Question 11

What is hereditary neuropathy and how does it present? *apparently common in exams*

Answer 11

• Autosomal dominant or recessive or X-linked - hundreds of mutations
• Pure motor, sensory, sensorimotor, small fibre and autonomic variants
• Demyelinating and axonal varieties
• Genetic testing available for the most common mutations e.g. CMT1a

Question 12

Name some examples of axonal neuropathies

Answer 12

• Idiopathic
• Vasculitic - ANCA+ve, rheumatoid arthritis, Sjogren’s syndrome
• Paraneoplastic - myeloma, breast cancer
• Infections - HIV, syphilis, lyme
• Drugs - alcohol, amiodarone, phenytoin
• Metabolic - diabetes, B12/folate deficiencies, hypothyroidism, chronic uraemia, porphyria

Question 13

Name some causes of autonomic neuropathy

Answer 13

• Chronic - diabetes, amyloidosis, hereditary
• Acute - GBS, porphyria

Question 14

How are axonal neuropathies treated?

Answer 14

• Treat cause
• Symptomatic treatment - physiotherapy, orthotics, neuropathic pain relief
• Vasculitic cause - pulsed IV methylprednisolone + cyclophosphamide

Question 15

How are demyelinating neuropathies treated?

Answer 15

IV Ig, steroids, azathioprine, mycophenalate, cyclophosphamide