Symmetrical peripheral neuropathy
A diffuse symmetrical pattern of damage to the nerves, most commonly the sensory nerves, which has a glove and stocking distribution. There is Schwann cell injury, myelin degeneration and axonal damage.
Sensory symptoms in the feet and legs are most com-mon and may be insidious or sudden in onset. In the case of the latter it may follow an episode of severe hyperglycaemia. Paraesthesia (pins and needles, burn-ing, shooting pains) which may be precipitated by normal sensations such as contact with bedclothes, this is called allodynia. The pain is worse at night and keeps the patient awake.
Chronic loss of sensation, most importantly of pain. The patient completely loses the sense of pain, so that severe damage such as burns, cuts, ulcers, infection and gangrene can occur without being noticed by the patient (the neuropathic foot).
On examination, there is reduced sensation, often in a glove and stocking distribution, and tendon reflexes may be reduced or absent. Vibration sense is often lost early in the course of peripheral neuropathy. Motor nerve damage causes muscle wasting. The feet and ankles in particular may be damaged.
This may be asymptomatic, accompanying the sensory neuropathy.
Painful neuropathy: It may also cause intense pain in a glove and stocking distribution.
A careful neurological examination should be carried out, including joint position sense, vibration, pinprick and light touch, tendon reflexes and muscle power. Most cases do not require further investigation as the cause is clear, however, occasionally it is appropriate to exclude other causes of the neuropathy e.g. by checking vitamin B12 level.
Improving glycaemic control may be of benefit. Pain can be treated by a stepwise approach using aspirin and codeine, tricyclic antidepressants, carbamazepine or gabapentin. Feet should be inspected and examined at each review including sensation to a 10 g monofilament or vibration and palpation of foot pulses. Examination may need to be repeated 1â€“3 monthly in high-risk pa-tients. New ulceration, swelling, discolouration is a foot care emergency and requires multidisciplinary assessment within 24 hours.
The acute form may resolve with time and better glycaemic control. The chronic form is persistent and irreversible. Symptoms may be intractable in some patients.