Sensory loss, pains, motor deficit and axonal regeneration in length-dependent diabetic polyneuropathy

Abstract

In order to learn more on the occurrence of pains and motor deficit in severe diabetic polyneuropathy we reviewed the data of a series of 30 diabetic patients with an uncommonly severe length-dependent diabetic polyneuropathy (LDDP). Extensive sensory loss predominated with pains and temperature sensations and affected all four limb extremities, anterior trunk in all, plus the top of the scalp in 9 patients and the cauda equina territory in 2. Twenty patients had neuropathic pains. Symptomatic autonomic dysfunction was present in 28/30 patients, mild distal motor deficit in 12 patients, severe in only one. Vibratory sensation was impaired in the lower limbs in 18 patients; position sense in 8. In the 10 nerve biopsy specimens, the density of myelinated axons was reduced to 23 % and that of unmyelinated axons to 8.5 % of control values. Regenerating axons accounted for 32.4 +/- 19.8 % of the myelinated fibres. On teased fibre preparations 13.9 % of fibres were undergoing axonal degeneration, while 29.4 % of fibres showed focal abnormalities of the myelin sheath.We conclude that distal motor deficit occurs only after major loss of sensory fibres in LDDP; the unmyelinated axons are predominantly affected; absence of clinical improvement contrasts with the high proportion of regenerating axons; detection of alteration of pain and temperature sensation in the feet seems the best method for neuropathy screening in diabetic patients.