5A. Polyneuropathies

Page created on June 3, 2021. Not updated since.

Definition and epidemiology

Polyneuropathies are disorders of the peripheral nerves, which usually affect the most distal parts of the body symmetrically.

They can be classified as either axonal or demyelinating. Axonal neuropathy occurs due to damage to the nerve axon, causing degeneration of the distal nerve and eventually denervation. Demyelinating neuropathy occurs due to demyelination, which causes slow conduction or conduction block.


  • Axonal polyneuropathy
    • Diabetic neuropathy
    • Alcoholic neuropathy
    • Toxic neuropathy
  • Demyelinating polyneuropathy
    • Inflammatory neuropathies
      • Guillain-Barre syndrome
      • Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP)
    • Hereditary neuropathies
      • Charcot-Marie-Tooth disease

Diabetic and alcoholic are the most common types.

Clinical features

Symptoms usually affect the distal parts of the body symmetrically. The clinical features depend on the specific type, but generally we can see weakness, atrophy, sensory loss, neuropathic pain, paraesthesia, and/or loss of reflexes.

In Charcot-Marie-Tooth disease, we can see foot drop, pes cavus deformity, and calf muscle atrophy.

Diagnosis and evaluation

ENG shows slow conduction in demyelinating neuropathies, and low amplitude potentials (denervation) in axonal neuropathy. However, ENG can only measure the function of thick nerves. For thin nerves, a skin biopsy is required.

In inflammatory neuropathies we can find high levels of protein but normal levels of cells in the CSF (albuminocytologic dissociation).


Treatment involves treating the underlying condition. Demyelinating neuropathies usually respond better to treatment.

Chronic inflammatory neuropathies are treatable and are treated with steroids, plasma exchange or IVIG.

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4B. Convulsive syncope

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5B. Subarachnoid haemorrhage (SAH)

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Neurology 2

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