Causes and clinical symptomatology of polyneuropathies

1. Big picture

A polyneuropathy is a generalized disorder of peripheral nerves that is usually symmetrical, length-dependent, and distal-predominant — it begins in the longest fibres (toes/feet) and ascends, producing the classic "glove-and-stocking" pattern.

The exam wants two things from this topic:

1. The causes, organized so you can rattle them off as a system (metabolic, toxic, inflammatory, infectious, hereditary, paraneoplastic, etc.).
2. The clinical symptomatology, i.e. how to recognize a polyneuropathy at the bedside and how to describe whether it is sensory, motor, autonomic, or mixed, and axonal vs demyelinating.

Core exam idea: Symmetrical, distal, length-dependent sensory loss with absent ankle reflexes = polyneuropathy. The two most common causes worldwide are diabetes mellitus and alcohol.

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