Contact thermography of painful diabetic neuropathic foot

To investigate regional differences in skin blood flow (measured by contact thermography) in the diabetic neuropathic foot and to examine the effect of foot temperature on the severity of neuropathic pain.

Thirty-five diabetic patients with painful polyneuropathy (PPN) and 33 healthy age- and sex-matched control subjects comprised the study. Mean foot temperature (MFT) in PPN (mean +/- SE 28.3 +/- 0.3 degrees C) was significantly higher (P less than 0.001) than in the control subjects (25.9 +/- 0.5 degrees C), with the highest temperatures over the metatarsal areas and heel. Visual analogue scale pain score (mean +/- SD 5.3 +/- 1.9 cm) did not correlate with MFT (r = -0.14, P = 0.52). In 10 patients with PPN followed for 2-8 mo (mean 4.6), MFT fell by 1.6 degrees C (P = 0.05), but pain scores did not alter.

Neuropathic pain is unaffected by alterations in skin temperature. Elevated skin temperatures at recognized sites of weight bearing (metatarsal heads and heels) are common in the diabetic neuropathic foot and may indicate tissue injury or inflammation induced by pressure trauma or increased arteriovenous shunting. Follow-up studies will determine whether thermographic hot spots are more susceptible to ulceration.