The effect of sensory nerve stimulation on sensory nerve function in people with peripheral neuropathy associated with diabetes

Objective: To assess the effect of sensory nerve stimulation in older people with peripheral neuropathy associated with diabetes (DPN). Materials and methods: A randomized, placebo controlled, double blind trial was used to assess the effect of 12 weeks of low frequency sensory nerve stimulation (LF-SNS) in the lower limb [International Patent Application No. PCT/AU2004/001079: 'nerve function and tissue healing' (Z. Khalil)]. Response to capsaicin, basal microvascular blood flow, electric cutaneous threshold and oxygen tension were assessed pre- and post-treatment and between limbs. Participants: People 55 years of age or older diagnosed with DPN: 35 active and 31 placebo participants. Results: Between groups comparisons: no significant differences occurred between stimulation groups. Within subject comparisons: in the active LF-SNS group, comparing stimulated to contralateral legs, there were significant increases in size of capsaicin flare [t(1,33)=3.65, p<0.05] and capillary blood flow [t(1,34)=-0.33, p<0.05]. There was a trend to improvement in time to initial flare response [t(1,34)=-1.86, p=0.07]. No changes were evident in the placebo group. Responder analyses: In a group of 'responders', the time to initial flare response (p<0.05, r=0.64), size of capsaicin flare (p<0.05 r=1.0) and microvascular blood flow (p<0.05, r=0.60) improved significantly after LF-SNS. Conclusions: The observed data suggest that LF-SNS improves nerve function in a subset of people with DPN. Targeting toward probably 'responders' may deliver the greatest benefit from short-term therapy. Testing optimal application in others seems warranted.