The Polyneuropathies Signs

SENSORY EXAMINATION

All modalities are tested Light touch

Two point discrimination Vibration sensation Joint position perception Temperature perception Pain perception.

Functions of large myelinated sensory fibres.

Functions of small unmyelinated and thinly myelinated sensory fibres.

Initially the area of total sensory loss is defined. The test object, e.g. a pin, should be moved from anaesthetic to normal area; it is more accurate to state when an object is felt rather than when it disappears.

In polyneuropathies, sensory loss is symmetrical and follows a characteristic stocking and glove distribution.

Examination of gait is important; with joint position impairment, X sensory ataxia is evident. Romberg's test is positive (see page 187). X

Neuropathic burns/ulcers or joints may be present.

Trophic changes

- Cold blue extremities.

- Cutaneous hair loss.

- Brittle finger/toe nails occasionally occur.

The axon reflex can be used to 'place' lesions in the sensory pathway. Normally:

the skin is scratched - local vasoconstriction (white reaction) 1 due to local next - local oedema (red reaction) j histamine release, and finally - surrounding vasodilatation or flare, dependent on antidromic impulses from the dorsal root ganglion along an intact sensory neuron.

Reflex vasodilatation (flare)

Reflex vasodilatation (flare)

1. A distal sensory lesion will result in an absent flare response.

2. A proximal root lesion will not impair the response.

Scratch

1. A distal sensory lesion will result in an absent flare response.

2. A proximal root lesion will not impair the response.

Scratch

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