Measurement of manipulative dexterity in patients with hand-arm vibration syndrome.

OBJECTIVES: The purpose of the study was to assess quantitative measurements of the manipulative dexterity of patients suffering from hand-transmitted vibration disorder, and to investigate a possible link with impaired tactile perception in their hands. SUBJECTS AND METHODS: The subjects were 30 patients with hand-arm vibration syndrome, 30 office workers and 20 manual laborers of similar ages. Manipulative dexterity was assessed by measuring the performance time of buttoning-unbuttoning a work jacket with five buttons and of picking up and transferring 30 red beans, one by one, with the fingers from one plate to another. Patients were also examined on vibrotactile thresholds at 125 Hz as well as pain thresholds. RESULTS: The buttoning-unbuttoning time and the bean transfer time were significantly prolonged in the patients compared with the worker groups. The patients showed a close correlation between the buttoning-unbuttoning time and the bean transfer time. Performance times did not differ between patients with vibration-induced white finger and those without it. Those times also correlated with the vibrotactile and pain thresholds in the patients. When a cut-off value was set at 2 SDs from the mean performance times of the manual laborers, exceeding the cut-off value was found in 70% of the patients for the button-unbutton test and in 80% of those for the bean transfer test. All patients with moderately or severely increased vibrotactile and pain thresholds exceeded that value in performing the two tasks. CONCLUSION: The present measurements quantitatively showed impaired manipulation in patients with hand-arm vibration syndrome. Such difficulty with manipulation seems to be associated with the impaired tactile sensation in their hands.

Thermal perception threshold testing for the evaluation of small sensory nerve fiber injury in patients with hand-arm vibration syndrome.

The aim of the present study was to investigate whether thermal perception threshold testing is a useful method that could replace pain threshold testing in the evaluation of small sensory nerve fiber injury in vibration-induced neuropathy. Vibration, pain, and thermal (warm and cold) perception thresholds were examined on both middle fingers of 50 patients with hand-arm vibration syndrome and 29 healthy controls of similar age. The patients were divided into three subgroups according to the Stockholm Workshop sensorineural scale. Thermal (warm and cold) thresholds as well as vibration and pain thresholds were significantly more deteriorated among the patients than in the controls. Among the patients, warm thresholds elevated and cold thresholds lowered according to the Stockholm Workshop scale. Thermal thresholds were significantly correlated with pain thresholds, and the sensitivity of the thermal threshold testing tended to be greater than that of the pain threshold testing. The present findings indicate that thermal threshold testing for warm and cold perception can be a useful substitute for pain threshold testing to examine small nerve fiber injury in vibration-induced neuropathy.

Medial plantar nerve conduction velocities among patients with vibration syndrome due to chain-saw work.

OBJECTIVE: The present study examined the effect of the vibration syndrome (VS) on the peripheral nervous system in the lower extremities. METHODS: Thirty-eight patients with VS due to previous exposure to vibration from chain-saw work and 55 age-matched controls were examined for sensory nerve conduction velocities in the medial plantar nerve (SCV-P). The patient group was divided into two subgroups, one with (n=19) and the other without vibration-induced white finger (VWF; n=19). RESULTS: Analysis of variance of SCV-P for the three groups showed significant difference (F(2,89)=10.65, P < 0.0001). A significant difference was found between the controls and the VWF(+) group (P < 0.0001) but not between the controls and the VWF(-) group (P=0.0508) by multiple comparison using Scheffe's method. CONCLUSION: These findings suggest that VS affects the peripheral nervous system function in the lower extremities via mediation of circulatory disturbance manifested as VWF.

Heart rate variability in response to psychological test in hand-arm vibration syndrome patients assessed by frequency domain analysis.

To investigate heart rate variability in response to psychological tests (Japanese version of Stroop color word test and mirror drawing test) in 29 hand-arm vibration syndrome (HAVS) patients, 16 of them with vibration-induced white finger (VWF) and 13 without VWF, and 10 healthy controls of similar age, heart rate variability during spontaneous and deep (6 cycles a minute) breathing in supine position before and after exposure to the psychological tests was examined calculating frequency domain components such as low frequency (LF) power-index of both the sympathetic and parasympathetic activity, high frequency (HF) power-index of the parasympathetic activity and LF/HF-index of the sympathovagal balance. The group of all patients and the group without VWF indicated significant increase in LF/HF in the deep breathing measurement after exposure to the psychological tests. The result suggests that the sympathetic tone in the sympathovagal balance predominated in the HAVS patients which means that they had larger sensitivity of the sympathetic nervous system to the psychological tests.

Affected segments of the median nerve detected by fractionated nerve conduction measurement in vibration-induced neuropathy.

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 0SN (no neurological symptoms) while 56% in 3SN (severe stage). The present study has demonstrated that vibration-induced 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.

Digital sensory nerve conduction velocity and vibration perception threshold in peripheral neurological test for hand-arm vibration syndrome.

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 an 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%.

Increase in plasma thrombomodulin level in patients with vibration syndrome.

To determine whether endothelial cells are injured in vibration syndrome, we measured plasma levels of thrombomodulin (TM) in 100 patients with this syndrome using one-step sandwich enzyme immunoassay. Plasma level of TM in patients with vibration syndrome was significantly higher than that in normal control (p < 0.0001). There was no significant difference in the plasma TM level between patients with vibration syndrome and those with collagen disease. Plasma TM concentration in chain-saw operators was significantly higher than that in rock-drill operators (p < 0.05). Plasma TM value did not significantly differ between patients with vibration-induced white finger (VWF) and those without VWF. These results suggest that endothelial injury is present in patients with vibration syndrome, the degree of endothelial injury in patients with vibration syndrome equals that in patients with collagen disease, and the endothelial injury in chain-saw operators is greater than that in rock-drill operators. However, there was no difference in the degree of endothelial injury between patients with VWF and those without VWF.

Involvement of the central nervous system in vibration syndrome.

In order to clarify the involvement of the central nervous system (CNS) in vibration syndrome (VS), patients with VS and age-matched controls were given a questionnaire and neurophysiological tests on auditory brainstem response (ABR), event-related potential (P300), short-latency somatosensory evoked potentials (SLSEP), and blink reflex (BR). Twenty-eight patients with a mean age of 56.3 (SD = 3.01, range 48-65) years from western Japan were examined. They had been on sick leave for an average of 6.13 (SD = 3.2, range 1-13) years at the time of the testing. Almost all were experiencing Raynaud's phenomenon in the winter of 1990-1991. They were not suffering from diseases or injuries which might have affected the CNS function. These patients were divided into two subgroups, one with more symptoms related to the CNS, especially memory and judgment (n = 13, group A), and the other with fewer symptoms (n = 15, group B). Normal controls with an average age of 55.8 (SD = 4.8, 48-65) years were people from the same area who met similar criteria. The ABR parameters of the patients were slightly, but not significantly, delayed compared with those of the controls. The SLSEP and BR parameters of the patients were not delayed. The latencies of P300 in group A were significantly delayed compared with those in the controls. The findings suggest that VS involves the cognitive and attention functions of the cerebral higher function, but not the conduction function in the auditory and somatosensory ascending tract and facial nerve reflex tract in the brainstem.

High level of plasma thrombomodulin (TM) concentration and correlation with endothelin (ET)-1 in vibration-exposed patients.

We measured plasma level of TM and ET-1 in vibration exposed patients. The results showed the plasma level of TM in vibration exposed patients was significantly higher than in normal controls. The present findings showed relatively wide damage of endothelial cells in the vascular bed of vibration-exposed patients. On the other hand, the mean level of ET-1 in these patients tended to be higher than in normal controls, though there was no difference. Further studies are necessary about the mechanism of endothelial damage in vibration syndrome patients and its contribution to peripheral circulatory disturbance of vibration syndrome including the role of ET-1.

Digital nerve conduction velocity for evaluation of peripheral nerve impairments in vibration syndrome.

In order to evaluate peripheral nerve impairments in vibration syndrome, sensory nerve conduction velocity (SCV) in the digital segment of the median nerve was measured by applying electrical stimulation to the wrist and recording from two pairs of electrodes attached to the middle finger. Fractionated SCVs were also measured in the palm-to-finger, wrist-to-palm, and elbow-to-wrist segments of the median nerve. Subjects were 65 patients with vibration syndrome and 48 healthy controls of similar age. SCVs in the digital nerve segment were significantly slower in the patients than in the controls. Significant slowing was also found in the wrist-to-palm segment. SCVs in the palm-to-finger and elbow-to-wrist segments did not differ between the two groups. Slowed SCVs were most frequently encountered in the digital segment (38% of the patients). The slowing in the wrist-to-palm segment was found in 20% of the patients. Present findings indicate that the digital segment is most frequently affected in vibration-induced neuropathy, and measurement of SCVs in the digital segment would serve to evaluate the peripheral neuropathy in vibration syndrome.

Nerve conduction velocities in the lower extremities among patients with vibration syndrome.

In order to clarify the effect of vibration syndrome (VS) on the peripheral nervous system (PNS) in the lower extremities, 59 patients with VS (age 58.5 +/- 5.1 years) and 49 age-matched controls (age 57.0 +/- 5.1 years) were examined for sensory nerve conduction velocities (SCV) in the sural nerve (SSCV) and the medial plantar nerve (PSCV) in the summer of 1993 and 1994. They had not been suffering from diseases and injuries which might have affected the SCV in the lower extremities. These patients were divided into two subgroups, one with past vibration exposure to chainsaw (N = 22) and the other with past vibration exposure to rock drills and other tools (N = 37). SCVs corrected by skin temperature were subjected to statistical analysis. In PSCV a significant reduction among all patients (40.8 +/- 4.24 m/s, p < 0.01) including two subgroups (chainsaw, 39.7 +/- 4.7 m/s, p < 0.01; rock drill and others, 41.0 +/- 4.6 m/s, p < 0.01) was observed compared with those of the controls (43.2 +/- 4.31 m/s), but there was no significant reduction in SSCV. Significantly more subjects with PSCV below the standard of PSCV (ten percentile value of those of the controls) were observed among all patients (17/59, 28.8%, p < 0.05) including two subgroups (chainsaw, 7/22, 31.8%, p < 0.05; rock drill and others, 10/37, 27.0%, p < 0.05) than in the controls (4/49, 8.2%). These findings suggested that VS affected the PNS function in the lower extremities and that its mechanism was considered to mediate a circulatory disturbance, and to differ from SCV reduction in the finger.

Raynaud's phenomenon of fingers and toes among vibration-exposed patients.

Eleven patients with Raynaud's phenomenon of the toes as well as the fingers were encountered among about 1,000 vibration-exposed patients. They consisted composed of four chain-saw operators, five rock drillers, a stone quarrier and a welder in a shipyard. All the cases were examined carefully for differential diagnosis, but there were no particular abnormalities in hematological, immunological and homodynamic examinations. The rock drillers, quarrier and welder had direct vibration exposure of the foot, which was considered to be responsible for their Raynaud's phenomenon of the toe. Four chain-saw operators, who had been little exposed to vibration of the foot directly, were examined further on skin temperature of fingers and toes every three hours except at night and in a 30-min cold provocation test at 5 degrees C. The skin temperature of both their fingers and toes was lower than in age-matched healthy controls. The chain-saw operators started to work in the 1960's and early in the 1970's, when the chain saw vibration level was high. It is, hence, considered that they were exposed to strong vibration of the hand from chain saws, and then suffered severe Raynaud's phenomenon of both fingers and toes.

Activation of blood coagulation and fibrinolysis in vibration syndrome.

The pathophysiology of peripheral circulatory disturbance in patients presenting with vibration syndrome was studied from the viewpoint of blood coagulation. Plasma levels of fibronectin (FN), vitronectin (VN), thrombin-antithrombin III complex (TAT), and alpha 2-plasmin inhibitor-plasmin complex (PIC) were measured in 23 subjects who showed no evidence of vibration-induced white finger [VWF(-) group] and in 24 patients who presented with VWF [VWF(+) group]. In the VWF(-) group, plasma FN concentrations were elevated but plasma TAT and PIC levels were within the normal ranges. In the VWF(+) group, plasma FN concentrations were normal but plasma TAT and PIC levels were significantly elevated. In both groups, plasma VN concentrations were similar to those in normal controls. For purposes of comparison, 32 patients presenting with diabetes mellitus were also studied. They were divided into 2 groups, 13 subjects who showed no evidence of angiopathy [complication(-) group] and 19 patients who presented with angiopathy [complication(+) group]. In the complication(+) group, plasma TAT and PIC concentrations were significantly elevated, as in the VWF(+) group. These results suggest that in vibration syndrome, vibration, cold stimulus, or other factors first injure the vascular endothelium, resulting in a rise in plasma FN, and that in the VWF(+) group, augmentation of coagulation and fibrinolysis induces a state of compensated disseminated intravascular coagulation (DIC).