A comparative electrophysiological and histological study of sensory conduction velocity and Meissner corpuscles of the median nerve in pneumatic tool workers

Triggering of Carpal Tunnel Syndrome Symptoms in Patients Using Urban Public Transportation

Background: Carpal tunnel syndrome (CTS) is the most common compressive neuropathy found in clinical practice. Recent studies evaluated which external factors could be involved in the CTS symptoms, including prolonged exposure to vibration, especially in the upper limb. This study investigated signs and symptoms in patients with CTS after using urban transport on (1) both upper limbs, (2) how long before these symptoms appear, and (3) the hands position or body reaction during the act of pressing the safety bars. Methods: The study was conducted from July 2012 to April 2013. A total of 205 (178 women and 27 men) patients were evaluated. CTS was diagnosed in 285 hands. All participants answered a questionnaire formulated by the authors. The questionnaire was applied by researchers who were single-blinded and not involved in the research. Results: Most of the participants (87%) were women, but there was no statistical significance in age between groups (women = 51.24 ± 8.47 years, men = 51.10 ± 6.52 years, P > .05). The symptoms appeared significantly in the first 15 minutes after boarding when compared with patients who had no symptoms during the journey. There was no difference between hands position along the journey and the onset of symptoms. Conclusions: The onset of symptoms in patients with CTS using urban public transportation most commonly occurred in the first 15 minutes after boarding. Public transport vibration seems to be, at least in part, directly related to the development of symptoms. Questionnaires for the assessment of paresthesia symptoms during the use of public transport may be useful for CTS diagnosis.

Neuropathological changes in vibration injury: an experimental study

Vibration syndrome, a clinical condition arising from chronic use of vibrating tools, is associated with a spectrum of neurovascular symptoms. To date, only its vascular pathology has been extensively studied; we sought to determine what direct neurologic injury, if any, is caused by vibration. Hindlimbs of anesthetized rats were affixed to a vibrating platform 4 h a day for 7 days. Study animals were vibrated with set parameters for frequency, acceleration, velocity, and amplitude; control animals were not vibrated. On day 7, nerves were studied by light and electron microscopy. While light microscopy showed minimal histologic differences between vibrated (n=12) and control (n=12) nerves, electron microscopic changes were dramatic. Splitting of the myelin sheath and axonal damage (e.g., myelin balls and "finger ring") were consistently seen in both myelinated and nonmyelinated axons. Despite relatively short vibration, definite pathology was demonstrated, suggesting that vibration syndrome has a direct neurologic component.

Vibration injury damages arterial endothelial cells

Prolonged exposure to hand-transmitted vibration can cause debilitating neural and vascular dysfunction in humans. It is unclear whether the pathophysiology involves simultaneous or sequential injury of arteries and nerves. The mechanism of vibration injury was investigated in a rat tail model, containing arteries and nerves structurally similar to those in the human hand. Tails were selectively vibrated for 1 or 9 days with the remainder of the animal at rest. One vibration bout of 4 h/day, 60 HZ, 5 g (49 m/s(2)) acceleration, injured endothelial cells. Injury was signaled by elevated immunostaining for NFATc3 transcription factor. Electron microscopy revealed that vibration for 9 days produced loss and thinning of endothelial cells, with activated platelets coating the exposed subendothelial tissue. Endothelial cells and arterial smooth muscle cells contained double membrane-limited, swollen processes indicative of vasoconstriction-induced damage. Laser doppler surface recording demonstrated that 5 min of vibration significantly diminished tissue blood perfusion. These findings indicate that early injury involves vasoconstriction and denuding of the arterial endothelium.

The prevalence of sensorineural symptoms attributable to hand-transmitted vibration in Great Britain: a national postal survey

BACKGROUND

Exposure to hand-transmitted vibration (HTV) can cause sensorineural symptoms in the upper limb, but its impact has not previously been assessed in the general population.

METHODS

To investigate, we mailed a questionnaire about exposures to HTV, finger blanching and sensory symptoms (numbness or tingling) in the upper limbs to a population sample comprising 21,201 working-aged men and women selected at random from the age-sex registers of 34 British general practices, and a further 993 randomly selected from the pay records of the armed services. Associations were explored using multiple logistic regression models to adjust for confounding, with the resultant odds ratios converted into prevalence rate ratios (PRs).

RESULTS

Of 12,907 respondents, 2,607 (20.2%) reported sensory symptoms in the upper limb during the past week. Sensory symptoms were more prevalent in those with blanching, and were commonly associated with exposure to HTV, especially in men. In comparison with men who had never been exposed to HTV, the PR in men exposed both at work and in leisure was 2.2 (95% CI 1.9-2.4). Associations were found even in those who had never blanched.

CONCLUSIONS

Sensorineural symptoms in the upper limbs are common. HTV is an important risk factor for such complaints in the general population.

Hand function in workers with hand-arm vibration syndrome

Hand-arm vibration syndrome has been specially addressed in the Scandinavian countries in recent years, but the syndrome is still not sufficiently recognized in many countries. The object of this preliminary study was to describe the nature and character of vibration-induced impairment in the hands of exposed workers. Twenty symptomatic male workers (aged 28 to 65 years) subjected to vibration by hand-held tools were interviewed about subjective symptoms and activities of daily living and were assessed with a battery of objective tests for sensibility, dexterity, grip function, and grip strength. The test results were compared with normative data. The majority of patients complained of cold intolerance, numbness, pain, sensory impairment, and difficulties in handling manual tools and in handwriting. The various objective tests showed considerable variation in indications of pathologic outcome, revealing differences in sensitivity to detect impaired hand function. Semmes-Weinstein monofilament testing for perception of light touch-deep pressure sensation, the small-object shape identification test, and moving two-point discrimination testing for functional sensibility provided the most indications of pathologic outcomes. The authors conclude that vibration-exposed patients present considerable impairment in hand function.

Association between a quantitative measure of tactile acuity and hand symptoms reported by operators of power tools

An association between a quantitative measure of tactile acuity at the fingertips and symptoms of reduced manipulative function, as established by responses to a questionnaire, was demonstrated in a population of 81 manual workers from the mining industry (62 power-tool operators and 19 nonusers). Mechanoreceptor-specific vibrotactile thresholds were determined for the slowly adapting type I (SAI) and fast-adapting types I and II (FAI and FAII) receptors at the fingertip of the third digit of each hand. Statistically significant threshold shifts in SAI and/or FAII acuity were found in persons responding affirmatively to questions concerning finger/hand numbness, blanching, and difficulty buttoning clothing. The best predictors of a quantitative change in tactile acuity were questions relating to difficulty manipulating small objects and buttoning clothing, yielding positive predictive values of from 90% to 100% and false positive rates of from 0% to 2.8%. The demonstration of an association between a quantitative measure of tactile acuity at the fingertips and some symptom reports, obtained by means of a questionnaire, provides the basis for the development of a screening procedure for persons at risk of such disturbances in hand function.

Carpal tunnel syndrome (CTS) and exposure to vibration, repetitive wrist movements, and heavy manual work: a case-referent study

Possible connections between carpal tunnel syndrome (CTS) and exposure to vibrating handheld tools, repetitive wrist movements, and heavy manual work were examined in a case-referent study. The cases were 38 men operated on for CTS between 1974 and 1980. For each case, two referents were drawn from among other surgical cases (hospital referents) and two further referents from the population register and telephone directory, respectively (population referents). Thirty four of 38 cases (89%) and 143 of 152 referents (94%) were interviewed by telephone. An increased prevalence of obesity, rheumatoid disease, diabetes, or thyroid disease was observed among the cases but most did not suffer from any of these disorders. CTS was significantly correlated with exposure to vibration from handheld tools and to repetitive wrist movements but showed a weaker correlation with work producing a heavy load on the wrist. A cause-effect relation between CTS and exposures to handheld vibrating tools and to work causing repetitive movements of the wrist seems probable. Some differences between hospital and population referents indicate that a case-referent study of this type could be biased by inappropriate selection of referents.