Enhancing sensation in diabetic neuropathic foot with mechanical noise

Localized low-level mechanical or electrical noise can significantly enhance tactile sensitivity in healthy young subjects and older adults. This phenomenon is termed stochastic resonance (SR). In this study, we examined the effect of SR on vibratory and tactile sensation in patients with moderate to severe diabetic peripheral neuropathy.

A total of 20 subjects were included in the study. The vibration perception threshold (VPT) test and the Semmes-Weinstein filament (SWF) threshold at the plantar surface of the left foot and the big toe were determined under two mechanical noise stimulus conditions: null (no noise) condition and at 10% lower than each subject's mechanical noise threshold of perception.

The baseline values (mean +/- SD) were as follows: Neuropathy Symptom Score (NSS) 5.2 +/- 2.5, Neuropathy Disability Score (NDS) 5.0 +/- 2.1, VPT 24 +/- 11 V, and SWF threshold 5.6 +/- 0.8 at the plantar surface of the foot and 5.3 +/- 0.9 at the big toe. The VPT improved significantly from 24 +/- 11 under null condition to 19 +/- 10 V with mechanical noise (P < 0.0001). Mechanical noise also significantly increased the number of detections of the SWF at the plantar surface of the foot (detection rate 66 +/- 11 vs. 59 +/- 15%, P < 0.02) but not at the big toe (63 +/- 10 vs. 61 +/- 16%, P = NS).

Mechanical noise stimulation improves vibration and tactile perception in diabetic patients with moderate to severe neuropathy. Additional studies are required to examine the effect of long-term noise stimulation on parameters of nerve function.