Peripheral neuropathy

Question 1

What is peripheral neuropathy?

Answer 1

Damage to one or more peripheral nerves

Most common cause = diabetes

Can be acute or chronic

Can be polyneuropathy or mononeuropethy

Causes:

• Diabetes
• Dietary deficiencies e.g. B12 or folate
• Medication: amiodarone, isoniazid, vincristine, nitrofurantoin, metronizadole
• CKD: electrolyte abnormalities
• Injury, infection
• Charcot Marie Tooth
• Freidreich’s ataxia

Clinical features:

Sensory: tingling/ numbness, loss of coordication, burning/ shooting pain, loss of temperature sensation

Motor: muscle weakness, muscle wasting, twitching and cramps, paralysis

Autonomic: dizziness/ fainting, anhidrosis, inability to tolerate heat, loss of bladder control, bloating, contipation, diarrhoea, impotence

Question 2

Investigations for peripheral neuropathy

Answer 2

Bloods: B12 and folate, FBC, U&E, glucose

Nerve conduction testing

Electromyography

Nerve biopsy

Skin biopsy

Question 3

Types of peripheral nerve injury

Answer 3

1. Wallerian degeneration: nerve degeneration occurs distal to an injury. Regeneration possible le if Schwann cell basement membrane remains
2. Segmental demyelination: Schwann cells are destroyed but the axon remains and regeneration can occur
3. Neuronopathy: neuronal cell body degeneration e.g. in MND
4. Axonal degeneration: can occur as a primary event or secondary to demyelination

Question 4

Causes of mononeuropathies

Answer 4

• Most common being radial, ulnar and medial and common peroneal
• Most commonly occurs when the nerve goes through anatomical narrowing e.g. carpal tunnel
• Conditions that lead to tissue oedema or thickening e.g. pregnancy, thyroid disease and amyloidosis increase entrapment

Question 5

Examples of focal neuropathies

Answer 5

Carpal tunnel syndrome

Trigeminal neuralgia

Ulnar entrapment

Peroneal nerve injury