Published online Apr 15, 2015. doi: 10.4239/wjd.v6.i3.391
Peer-review started: July 25, 2014
First decision: September 16, 2014
Revised: September 18, 2014
Accepted: January 18, 2015
Article in press: January 20, 2015
Published online: April 15, 2015
Processing time: 270 Days and 11.5 Hours
The diabetic foot is characterised by painless foot ulceration and/or arthropathy; it is a typical complication of painless diabetic neuropathy. Neuropathy depletes the foot skin of intraepidermal nerve fibre endings of the afferent A-delta and C-fibres, which are mostly nociceptors and excitable by noxious stimuli only. However, some of them are cold or warm receptors whose functions in diabetic neuropathy have frequently been reported. Hence, it is well established by quantitative sensory testing that thermal detection thresholds at the foot skin increase during the course of painless diabetic neuropathy. Pain perception (nociception), by contrast, has rarely been studied. Recent pilot studies of pinprick pain at plantar digital skinfolds showed that the perception threshold was always above the upper limit of measurement of 512 mN (equivalent to 51.2 g) at the diabetic foot. However, deep pressure pain perception threshold at musculus abductor hallucis was beyond 1400 kPa (equivalent to 14 kg; limit of measurement) only in every fifth case. These discrepancies of pain perception between forefoot and hindfoot, and between skin and muscle, demand further study. Measuring nociception at the feet in diabetes opens promising clinical perspectives. A critical nociception threshold may be quantified (probably corresponding to a critical number of intraepidermal nerve fibre endings), beyond which the individual risk of a diabetic foot rises appreciably. Staging of diabetic neuropathy according to nociception thresholds at the feet is highly desirable as guidance to an individualised injury prevention strategy.
Core tip: The diabetic foot is characterised by painless ulcers and/or arthropathy. Although painless diabetic neuropathy is known as the underlying condition, little is known quantitatively about the pain evoked by noxious stimuli (nociception) at the diabetic foot. Preliminary evidence shows that pinprick pain perception threshold at plantar digital skinfolds is supranormal, beyond the upper limits of measurement. It is suggested that measuring nociception at the foot in diabetes could specify the individual risk of painless ulcers and/or arthropathy and, thereby, provide the basis of an individualised graded injury prevention strategy.