Nociception at the diabetic foot, an uncharted territory
摘要
The diabetic foot is characterised by painless footulceration and/or arthropathy; it is a typical complicationof painless diabetic neuropathy. Neuropathy depletesthe foot skin of intraepidermal nerve fibre endings of theafferent A-delta and C-fibres, which are mostly nociceptorsand excitable by noxious stimuli only. However, someof them are cold or warm receptors whose functionsin diabetic neuropathy have frequently been reported.Hence, it is well established by quantitative sensory testingthat thermal detection thresholds at the foot skin increaseduring the course of painless diabetic neuropathy. Painperception （nociception）, by contrast, has rarely beenstudied. Recent pilot studies of pinprick pain at plantardigital skinfolds showed that the perception thresholdwas always above the upper limit of measurement of 512mN （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.