Peripheral neuropathy in the hand has often been reported in workers using hand-held vibrating tools. But the affected location in the hand is not clearly demonstrated. To elucidate the impaired segment of the median nerve within the hand, fractionated median sensory nerve conduction velocity (SCV) was measured in the digital, finger-to-palm, palm-to-wrist and wrist-to-elbow segments. Subjects were 56 patients with hand-arm vibration syndrome and 43 healthy controls of similar age. SCV in the digital and the wrist-to-palm segments was significantly slower in the patients than the controls. Slowed SCV in the digital segment was encountered in 36% of the patients, while the slowing in SCV in the wrist-to-palm segment (across the carpal tunnel) was found in 20% of them. The slowing in the digital segment was more frequently encountered in the advanced stage of the Stockholm sensorineural (SN) stage for hand-arm vibration syndrome: 10% in OSN (no neurological symptoms) while 56% in 3SN (severe stage). The present study has demonstrated that vibrationinduced nerve impairments dominantly exist both in the digits and across the carpal tunnel. Careful neurophysiological assessment is important to confirm the impaired location within the hand.

Circulatory disturbances of the foot in patients with vibration syndrome were studied by measuring the skin temperature of both index fingers and great toes through a 3-min immersion of the right foot in cold water at 10 degrees C. Subjects included 11 patients with vibration-induced white finger (VWF) [VWF(+) group], 12 patients without VWF [VWF(-) group], and 20 healthy referents not exposed to vibration. Patients were all male chain saw operators who had scarcely been exposed to vibration of the foot. The prevalence of coldness felt in the upper and lower extremities was greater than 90% in the VWF(+) group, about 60% in the VWF(-) group, and less than 10% in the referents. The extent of the coldness was greatest in the VWF(+) group. The skin temperature of both fingers and toes was lowest in the VWF(+) group, somewhat higher in the VWF(-) group, and highest in the referents both before and after immersion. These findings indicate that patients with vibration syndrome, especially those with VWF, have circulatory disturbances in the foot as well as in the hand. The disturbances in the foot may be related to long-term repeated vasoconstriction in the foot induced by hand-arm vibration through the sympathetic nervous system.

To evaluate peripheral neuropathy in patients with vibration syndrome, an examination was conducted of sensory nerve conduction velocity (SCV) in the digital segment of the median nerve in the middle finger and vibration perception threshold (VPT) at 125 Hz on the same middle fingertip. In addition, possible correlations were investigated between the two measurements. SCVs in the digital segment were measured by stimulating at the wrist electrically and recording from two pairs of electrodes in the finger. Fractionated SCVs were also measured in the palm‐to‐finger, wrist‐to‐palm, and elbow‐to‐wrist segments. The subjects were 52 patients with vibration syndrome and 40 healthy controls of similar age. SCVs in the digital segment and the wrist‐to‐palm segment were significantly slower in the patients than in the controls, and VPTs were higher in the patients. The strongest correlation of VPTs with SCVs among nerve segments measured was shown in the digital segment. With all increase in VPTs. SCVs in the digital segment tended to be slower, and slowed digital SCVs were encountered more frequently: 13% in VPTs below 5.0 dB and 56% in VPTs above 17.5 dB. Slowed digital SCVs were found in 43% of the patients and increased VPTs were encountered in 92%. © 1996 Wiley‐Liss, Inc.

These findings suggest that VS affects the peripheral nervous system function in the lower extremities via mediation of circulatory disturbance manifested as VWF.

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