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.
Highlights
MethodsBodily sensation is important for activities which are involved in normal movements and the protection of the body from nociceptive stimuli
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
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
Summary
Sensation is important for activities which are involved in normal movements and the protection of the body from nociceptive stimuli. Collecting information from the various senses is impaired by peripheral neuropathies, such as stroke, physical trauma, and diabetes mellitus. Nerve conduction velocities were used to diagnose sensory nerve disturbance. Recent investigations have elucidated the possible causes of such neurological disorders: a drop in blood supply to peripheral nerves and/or hyperglycemia toxicity may underlie impaired nerve fiber conduction. Superficial sensory impairment begins from the distal ends of the limbs and is characterized by dulling of vibratory and tactile sensation [4]. According to Dobretsov et al, the average median nerve conduction velocity of patients with diabetic neuropathy having sensory impairment is 53.2 m/s [5]. Clinical observation suggests that the dulling of superficial sensation is associated with a decrease in nerve conduction velocity. We reduced the conduction velocity of the median nerve afferent fibers through percutaneous cooling of the median nerve and investigated its effect on superficial sensation in the second finger, which is innervated by the median nerve
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