Ills which affect nerves are likely to do so in proportion to their length, that of the axon so far as the individual nerve cell is concerned. Thus a neuropathy arising from a humoural factor is prone to display itself first in the fingers and toes, hands and feet, forearm and leg before arm, thigh torso and so on.
The distribution of sensory neuropathy at the periphery therefore may be expected to show in the anatomical territory of a single nerve, or of particular nerves, or in a glove and stocking distribution. Conclusions drawn when it is clearly not an anatomical distribution of one of those sorts include factitious disorder and plumbus oscillans but it sometimes arises from a difficulty in giving or getting a clear history or results of an examination.
Toxic effects of chemo-therapeutic agents, or anticancer and other drugs are another major class of causes.
As well as the presence at all or in excess of a substance, a deficiency of a vitamin or other essential component may produce neuropathy.
Sensory neuropathy is more common than motor or autonomic, at the periphery.
The patient will probably notice it, but it may be discoverable by questioning or examination before they mention it. Diminished sensation, clumsiness, and disordered sensation with burning or tingling may be presenting features.
It is often easy to map out the distribution of numbness - loss of light touch - by lightly touching the skin with a finger. More subtle tests involving a whisp of cotton wool, a pin, vibration and warmth and cold have their place. A moderately clever way to standardise light touch is the use of a short piece of nylon monofilament fishing line chosen to buckle under 10 grams force. Nylon monofilament is sold at $6 for 330 yards, or for several pounds for 10 1cm pieces.
Treatment and management
If a remediable cause is identified, remedy it. Commonly the problem is to avoid progression and damage to the feet. Actual inspection of them, and involvement of a chiropodist are desirable, and the cobbler is also important.
Neuropathic foot ulcers are expensive as well as unpleasant and potentially lethal.
This article is a stub. Please feel free to expand it and make it more encyclopaedic.