A Study of Intra-dermal Injection of Botulinum Toxin Type A for the Diabetic Neuropathic Foot Pain

Overview

Effective treatment of neuropathic foot pain in diabetic patients is very important to improve their quality of life. There are many medications used to reduce the diabetic neuropathic pain, including anticonvulsants, anti-depressants or analgesics, but none is universally satisfied. A few previous studies employing BOTOX® i.d. injection for control of trigeminal neuralgia, post-herpes neuralgia indicate that BOTOX® was effective in controlling neuropathic pain. Intradermal injection of BOTOX® to the dorsum of the foot in diabetics should be effective in controlling diabetes-associated polyneuropathic pain of the foot.

Design: The present study is a single-center, randomized, double-blinded, cross-over study of BOTOX® in diabetic neuropathic foot pain. Pain Assessment: Subjective intensity of neuropathic pain was rated by a 100 mm visual analogue scale (VAS, 0 = no pain, 100 = unbearable pain). To assess the somatosensory effect of botulinum toxin, we also performed aserial somatosensory evaluations upon bilateral medial (L5 dermatome) and lateral (S1 dermatome) dorsum of the feet, and bilateral medial calves (L4 dermatome). Tactile threshold (TT) values of were assessed by von Frey filament, applied in an ascending and descending order of magnitude. The force required to bend the filaments was converted to log units for further comparison. Pain threshold (PT) to static mechanical stimuli was also determined by von Frey filament upon the above test sites to evaluate the severity of cutaneous allodynia. All subjects underwent the subjective pain rating and somatosensory evaluations (TT and PT) at baseline and each follow-up stage. Treatment: Treatments will consist of intradermal (i.d). injections of BOTOX® after topical anesthesia over randomly selected 15 patients and saline placebo over the other 15 patients. Dose will be 0.5-1U/cm2 BOTOX®, at total dose of 50 U/foot. A follow-up visit and assessment will be performed at 1, 4 8, 12 weeks following treatment during which the previous tests will be repeated. A cross-over of injection in the Botox group and saline group will be taken at the 12th week and then repeat the assessments at 1, 4, 8, 12 weeks. Analysis: Comparison between treated feet and non-treated feet based on QVAS and pain sensitivity test and life quality questionnaire by chi-square analysis. The summary of proposal is as below. Botox: 1. intradermal injection after Topical anesthesia, EMLA 2. 1 cc syringe with 30-gauge needle 3. 50 U/foot 4. 12 points/foot (3×4) A total of 30 cases (15 Botox group, 15 saline group and cross-over 12 weeks later)