Skin and muscle vasomotor reflexes in detecting autonomic dysfunction in leprosy

There are few tests to assess the function of small unmyelinated nerve fibe rs. One established test is the skin vasomotor reflex (SVMR), which uses la ser doppler flow velocimetry, The SVMR has the disadvantages of being susce ptible to interference (from change of temperature and alerting stimuli) an d of requiring expensive equipment. An ultrasound doppler method, which is less expensive, can be used to detect muscle vasomotor reflex (MVMR) activi ty. We sought to compare the efficacy of these two methods in detecting dys function of small unmyelinated nerve fibers in patients with leprosy. SVMR was shown to be less sensitive (P < 0.01) and specific (P < 0.001) than MVM R. The favorable results of MVMR may be attributed to its lesser susceptibi lity to interfering sympathetic vasoconstriction from alerting stimuli. MVM R also reflects larger areas of blood vessel innervation than the laser dop pler method. In leprosy, nerve damage is typically patchy and may be missed by the smaller sampling of the laser method, (C) 2000 John Wiley & Sons, I nc.