Sensory perception testing by monofilaments in the digits of controls and workers with HAVS

Abstract

Objective To determine if heavy manual work affects sensory perception in the digits and whether Semmes-Weinstein monofilaments (SWM) can be used as a screening tool to detect sensory neuropathy in the digits of workers exposed to hand-transmitted vibration (HTV). Methods A cross-sectional study of office workers, heavy manual workers not exposed to HTV and workers with handarm vibration syndrome (HAVS). Sensory perception was measured in the digits by SWM using a forced-choice method to determine variability by sex, age, hand and digit. Frequency distributions were used to determine limit values and linear weighted kappa for intra-digit variability. Poisson regression was used to explore the relationship between sensory perception by SWM and abnormalities of thermal and vibration perception in the hands of workers with HAVS. Results The sensory perception threshold of office workers did not vary by hand or digit. It was significantly lower in women < 30 than women aged ≥ 30 years. The 95th percentile for heavy manual workers was 1.00 (95% CI 0.60-1.00) and significantly higher than for office workers at 0.16 (95% CI 0.16-0.16). Heavy manual workers > 50 years had the highest threshold at 1.40 (95% CI 1.00-2.00). Weighted kappa for reliability was 0.63 (95% CI 0.53-0.70). A mean SWM threshold of ≥ 1.0 gram-force had a 79% sensitivity and 64% specificity for detecting abnormalities of thermal and vibration perception in the ipsilateral index and little fingers of workers with HAVS. Conclusions SWM are a useful screening tool for detecting sensory loss in the digits of workers exposed to HTV.

Applied Force Alters Sensorineural and Peripheral Vascular Function in a Rat Model of Hand-Arm Vibration Syndrome

“…These findings are similar to those of a number of other studies showing that exposure to vibration and/or pressure tend to induce discomfort (ie, reductions in the threshold) before inducing longer-term losses in sensitivity to tactile stimuli 6,59,72–75 . Studies examining longer exposures, or studies combining vibration and applied force, might generate the pattern of changes in sensorineural function that we have previously seen with this model (an increase in sensitivity followed by a reduction 46,76 ) and in humans 6,25,59,77 …”

“…These findings are similar to those of a number of other studies showing that exposure to vibration and/or pressure tend to induce discomfort (ie, reductions in the threshold) before inducing longer-term losses in sensitivity to tactile stimuli. 6,59,[72][73][74][75] Studies examining longer exposures, or studies combining vibration and applied force, might generate the pattern of changes in sensorineural function that we have previously seen with this model (an increase in sensitivity followed by a reduction 46,76 ) and in humans. 6,25,59,77 In conclusion, the results of this study show that application of force within the range seen at the fingertips of workers using hand tools 15,61,78 affects both blood flow and sensorineural function and that the effects are dependent on the amount of pressure.…”

A Review of Hand–Arm Vibration Studies Conducted by US NIOSH since 2000

“…They include using measures of blood flow using laser doppler [ 254 – 256 ] and changes in finger systolic blood pressure in response to cold exposure and rewarming [ 133 , 199 , 200 , 257 – 267 ]. Tests of sensorineural function include; nerve conduction [ 173 , 203 , 268 – 272 ], vibrotactile sensitivity [ 95 , 192 , 273 – 279 ], and tactile sensitivity using von Frey or Semmes Weinstein monofilaments [ 280 , 281 ]. Measures of changes in dexterity have been made using the Perdue Pegboard test and other tests looking at the ability to perform everyday tasks such as buttoning a shirt or zippering a jacket [ 187 , 188 , 282 , 283 ].…”

“…Tests of touch or applied pressure have also been used to detect changes in sensorineural function after exposure to occupational HTV in humans diagnosed with HAVS [ 280 , 281 ] and in animals exposed to vibration [ 201 , 217 , 238 , 310 ]. In humans, sensitivity to tactile stimulation or applied pressure is usually measured with von Frey or Semmes Weinstein monofilaments [ 223 , 280 , 281 ]. Both these tests involve placing a monofilament of a specific tensile strength on the body area to be tested.…”

“…This stimulus is applied first in an order where the tensile strength of the filament is increased until the subject responds, and then in descending order, where a filament that induces a response is used first, and the tensile strength is gradually decreased until the subject does not respond. Studies using monofilament have shown that workers with HAVS display a reduced sensitivity to touch or applied pressure [ 223 , 280 , 281 ]. However, studies using monofilaments to examine changes in tactile sensitivity in the NIOSH rat tail model did not find effects of vibration exposure on tactile sensitivity, even when there was evidence of nerve damage and changes in the CPT [ 201 ].…”