EMLA partially relieves the pain of EMG needling

Abstract

The aim of this study was to evaluate the efficacy of the topical analgesic cream EMLA in alleviating the pains caused by needling in electromyography (EMG). During the course of regular neurophysiology clinics, 34 Caucasian patients of both sexes, aged 21 to 69 yr (mean 38.5 ± 11.4 SD), scheduled for electromyography, were studied. The EMLA was spread thickly on two EMG sites on each arm: E site, on the lateral dorsal aspect of the forearm and A site, on the thenar eminence. Randomization was pre-established. Whenever EMLA was applied blindly on one of the sites of the arm, the placebo was applied on the homologous site of the other arm. After at least 45 min of application (range 45-145 min, mean = 72.3 ± 22.2), the needle was inserted into the skin and into the muscle. Then the electromyographist asked the patient to score his degree of pain on a visual analogue scale (VAS 1-10 cm) for each level of insertion. The results showed that on the skin of E site, the pain was less after EMLA than placebo (VAS = 0.75 ± 1.36 vs 3.10 ± 1.75, P = 0.0001). The untreated E site (placebo) was less sensitive than the untreated A site (VAS = 3.10 ± 1.75 vs 6.09 ± 1.96, P = 0.0001). Muscle insertion on E site was less painful on the EMLA sites than placebo (VAS = 2.83 ± 2.45 vs 5.73 ± 2.30, P = 0.0001). The VAS scores for skin and muscle insertion on A site were identical whether EMLA or placebo had been applied. We did not find any correlation between duration of application and VAS scores. We conclude that EMLA application is effective in easing the pain of EMG needling in the skin and extensor digitorum muscle at the forearm but is ineffective when applied for the time allotted in the present study to the skin of the palmar surface of the hand or over the muscle abductor brevis pollicis. © 1992 Canadian Anesthesiologists.