Abstract

Background: Effects of cooling on the conduction velocity of median nerve afferent fibers, and sensitivity of superficial tactile sensation in the innervated areas were investigated in ten healthy adults.
Methods: Superficial tactile sensitivities were examined using Spearman type calipers, quantitative sensory pinprick stimulation, and Semmes-Weinstein monofilament on the ventral side of the distal joint of the second finger, which is innervated by the median nerve. Tests were repeated four times: before cooling and after 3, 6 and 9 minutes of cooling.
Results: The nerve conduction velocity was 69 ± 6.71 (mean ± SD) m/s before cooling and reduced to 57.8 ± 4.2 m/s after 9 minutes of cooling. In contrast, superficial sensory impairment was not detected after cooling by any of the methods examined. In two of the ten cases, nerve conduction velocity was reduced to the level observed in diabetic neuropathy, at which clinical superficial sensory impairment has been shown to occur (~50 m/s), but no elevation of the sensory threshold was observed.
Conclusion: This study suggests that superficial sensation has a higher resistance to axonal decreases in nerve conduction velocity in response to cooling than was clinically assumed in peripheral neuropathy.