Evaluation of thermal and vibration sensation in diabetic neuropathy

Sensory evaluation of diabetic neuropathy was undertaken by a new technique for assessment of thermal sensitivity. The method is simple and reproducible, and the mean normal value of the lateral border of the foot was 6.0 degrees C (3.6-9.8 degrees C, 95% confidence limits). Four groups of patients with diabetic neuropathy were examined: 22 with neuropathic ulcers and/or Charcot joints (groups 1 and 2); all showed severe abnormalities (range 10.8- greater than 30 degrees C), frequently more than three times the upper limit of normal. In contrast thermal sensitivity in 15 patients with painful neuropathy (group 4) varied from normal to grossly abnormal (range 3.9- greater than 30 degrees C) confirming this form of neuropathy as a distinct entity. The majority of those 10 patients with autonomic neuropathy alone (group 3) had abnormal thermal sensitivity (range 6.4- greater than 30 degrees C). Comparison of thermal sensitivity (a small fibre modality) with vibration perception threshold (a large fibre modality) showed that thermal sensitivity is sometimes selectively affected, especially in those with painful neuropathy, suggesting that the small fibres are more vulnerable in diabetes. Frequent involvement of the hands confirms the "stocking and glove" distribution of diabetic neuropathy. We conclude that impairment of thermal sensitivity is the rule in symptomatic diabetic neuropathy and its assessment provides a simple quantitative measurement suitable for long-term studies of its natural history.