Clinical assessment of suspected damage from hand-held vibrating tools.

EKENVALL L. Clinical assessment of suspected damage from hand-held vibrating tools. Scand J Work Environ Health [3 ([987) 27[-274. The case history is still the cornerstone in the clinical assessment of suspected vibration injury. Objective tests to verify the symptoms are needed for legal reasons in insurance cases and for research purposes. The minimum requirement of a test used to obtain objective signs of Raynaud's phenomenon is that patients with vibration-induced white finger be evaluated along with symptom-free, but vibration-exposed, subjects for reference. The measurement of systolic blood pressure in the finger after local finger and general body cooling is a test that has been evaluated in this way, as has restitution of fingertemperature after localcoolingand ischemiacombined withgeneralbody heating. If neurological symptoms are present, electroneurographic examination is essential since carpal tunnelsyndrome, a treatable condition,is common in vibration-exposedpatients. Measurements of vibration and temperature thresholds are complementary examinations. The so-calledvibrogram may be a method with which to obtain objective neurological signs of vibration injury, but the test needs further evalua tion. Untilmore isknownof the pathophysiologicalmechanismsbehind the disease, the patient's descrip tion of his symptoms, combined with a detailed exposure history, will remain essential for a diagnosis of vibration injury - irrespective of the results of the tests used.

Long-term use o f vibrating tools often lead s to th e development of vibration syndrome. The mo st wellknown of th e symptoms included in the syndrome is Raynaud's phenomenon (38), ie, attacks of white fingers induced by cold [called vibration-induced white finger (VWF) when caused by work with hand-held vibrating tools]. Hand-arm vibrat ion also affects the ner ves of the hands (50,51,52). Decreased sensitivity to vibration (53), temperature (29), or touch (II, 58) ha s been found in vibration-exposed workers . The frequen cy of carp al tunnel syndro me or other neuropath y (1, 9,19,34,61) is also increased among vibrationexpo sed wo rkers. Hand-arm vib ratio n ma y a ffect mu scles (20, 2 1, 32, 51) and contribute to osteoarthrosis (23). Symptoms from the central ner vous system have been discussed as being caused by work with vibrating tools (36,37), but mo st researchers den y any causative connection between vibration expo sure and such symptoms (8). An incr eased hearing loss seems to exist among vibration-expo sed workers with Raynaud' s phenomenon when th ese workers are compared with symptom-free workers from the same occupations with sim ilar expo sure times (31,49).
Thi s paper deals with the clinical assessment of Raynaud' s phenomenon and neurological symptoms in workers exposed to hand-arm vibration .

Case history
Case history is the cornerstone of the clinical assessment of suspected vibration injury. Que stionnaires can be used in screening surveys of exposed groups, but they cannot replace direct contact between the ph ysician and the patient. A detailed exposure history and the patient's description of symptoms are essential. The information on exposure to vibrating tools must include the number of years in exposed work , type(s) of tools used, and, if no objectiv e registration can be obtained, the patient's estimation of daily exposure time .
The medical history should be recorded with special emphasis on causes other than hand-arm vibration for the existing symptoms (10,12). The physical examination should include a neurological examination (sensibility and motor function of the hands), palpation of the radial artery (due to the possibility of thoracic outlet syndrome) and ulnar artery (Allen's test) . The patient's smo king habits should be noted.

Vasospastic disease
Any cold -induced symptoms should be graded according to an internationally known symptom scale. The Taylor-Pelmear symptom scale (55) -now appearing in a revised version (22) -is the best known of these assessment schemes, but other scales are sometimes used (46,54). Those including symptoms from the central nervous system cannot be used international-Iy, since such symptoms are not recognized by all researchers as belonging to the vibration syndrome (54). The existence of different symptom scales is unfortunate, since no test for Raynaud's phenomenon is ideal or universally accepted. One internationally accepted and consistently used symptom scale would greatly facilitate the comparison of epidemiologic studies, dose-effect studies, and studies on different diagnostic procedures.
Cold provocation tests are often used to obtain objective signs of Raynaud's phenomenon. Time-consuming, drastic, and, for the patient, very uncomfortable cooling procedures are needed to provoke an attack in the laboratory (28,46). Therefore researchers have tried to find tests that, without provoking an attack, can demonstrate a changed reactivity to cold (27,28,33,41,43). Men working with vibrating tools, irrespective of whether they have VWF or not, seem to have an increased reactivity to cold in comparison to unexposed healthy referents (12,24). Thus any test used to diagnose VWF must be evaluated with vibration-exposed but healthy persons as reference.
The measurement of systolic blood pressure in the finger after general body and local finger cooling (13,42,44,45) is the test preferred in our laboratory. It gives few falsely positive results in exposed (or unexposed) referents, but about 25 010 falsely negative results in patients with a reliable history of VWF (15,57). The test results might be influenced by the patient's smoking habits in that nonsmokers have a higher frequency of normal test results (14).
The measurement of temperature restitution after a hand has been cooled during ischemia and general body heating is a test that, on a group basis, demonstrates a difference between VWF patients and healthy referents (35,60). A similar test, but without body heating, separates VWF patients and vibration-exposed referents on a group basis (24). Other cold provocation tests have also been used, eg, the cold pressor test (43), the nail compression test (27), and the measurement of finger blood pressure after local cooling, general heating, and the oral administration of alcohol (4).
Other techniques used have been angiography or fluorescein angiography to visualize spastic or organic lesions in finger arteries. Plethysmography, flow measurement with Doppler ultrasound or the laser-Doppler technique can be used to study blood flow in the fingers. None of these techniques has been systematically evaluated in VWF.
As yet, no test can separate VWF from primary Raynaud's disease on an individual level. A person with long-term exposure to vibrating tools, who has developed attacks of white fingers, must be considered as having VWF if no other cause for the symptoms can be demonstrated. VWF can be safely excluded if the symptoms started before the vibration exposure. Agate (2) described cases of white fingers developing in patients who had stopped working with vibrating tools, 272 but recent studies have consistently shown an amelioration of vasospastic symptoms after the cessation of work with vibrating tools (18,48). Thus symptoms starting more than a short time after the cessation of exposure have probably not been induced by vibration.

Neurological symptoms
Neurological symptoms, mainly in the form of paresthesias in the hands and arms, are even more common in vibration-exposed patients than in unexposed referents (6,25). Paresthesias directly after the use of a vibrating tool are common. Sleep-disturbing paresthesias nightly are typical for carpal tunnel syndrome and common in cases of vibration syndrome. Loss in manipulative skill may also occur (5) and must be separated from sensibility disturbances caused by vasospastic reaction in the cold. A separate scale for the classification of neurological symptoms in the handarm vibration syndrome has now been devised (7).
Since carpal tunnel syndrome is common in vibration-exposed patients (3,9), electroneurographic and electromyographic examinations are necessary for all patient s with symptoms consistent with this syndrome. Since the patients often cannot localize the symptoms to median innervated areas only, electroneurography must not be restricted to typical cases.
The vibrogram, ie, the measurement of vibration sensitivity in the finger pulp at different vibration frequencies, has lately been shown to be a sensitive technique to demonstrate early carpal tunnel syndrome (39,40). The technique has been used for vibration-expo sed patients (26) but needs further evaluation in symptomfree vibration-exposed workers before it can be recommended for routine clinical use. The measurement of temporary vibration threshold shift after acute vibration exposure separates patients with symptoms from healthy referents on a group basis better than the determination of permanent vibration thresholds (37). Measurements of temperature thresholds give many pathological results for vibration-exposed patients with neurological symptoms (16,29,30) and therefore indicate that damage to small myelinated and unmyelinated nerve fibers is common in the vibration syndrome. Further evaluation of this technique is also necessary. Temperature and vibration thresholds (possibly after acute vibration exposure) are comparatively easy to measure quantitatively and might be used for screening exposed groups, even outside the hospital, to detect sensory disturbances early. Vibration thresholds are, however, dependent on skin temperature (59). Skin temperature is lower in VWF patients than in healthy referent s even without any induced cold stimulus (17) and thus must be controlled. Moreover, the thresholds are changed by vibration exposure, and any testing must be performed with a standardized latency period since the last work with exposure to vibration.
In the cas e o f the a p peara nce of the vib ration syndrome, vibratio n exposure sho uld be sto pped or min im izcd sinc e th ere is evidence th at vaso sp astic sym ptoms improve or disappear in many cases after th e cessatio n of exposure . Many yea rs see m to be needed before a n ame lio ratio n of the sym pto ms ca n be expected ho wever (18,47). Since VWF attack s a re induced by co ld, it is probably rational to advise th e patient to av oi d occupations in vol ving exposure to cold. There is so me evide nce that nicotine mi gh t aggra vat e vasospastic sym pto ms (14 , 56) , and the a voidance of nicotine is recommended .
Ap art fro m carpal tunnel syndro me, which ca n often be suc cessfully treated with an operation , there exist s no tre a tment for the neuropathy that appears with the vibr ation synd rome. There are indications that neurological sym ptom s do not easily di sappear after the cessation of vibration exposure (25,48). If this possibility ca n be verified, patients with signs of neuropathy mu st avoid vibrating tools at a n early stage.
Suggestions for the "minimum examination" necessary for suspected vibration syndrome As sta ted in the preceding text, th e case history is the corner stone of the diagnosis of sus pected vibra tion synd ro me. Detailed exposure data, th e pati ent ' s descri ptio n o f sym ptoms , and a ph ysical exa mina tion to exclude other possible causes for th e sympto ms ar e esse ntia l. C ircula to ry and neurolog ical sym pto ms sho uld be cla ssifi ed ac cording to sympto m sca les , pr efe rably intern a tio na lly accepted ones. Objectiv e test s to veri fy Raynaud' s ph enomenon a rc nece ssary for legal reas o ns in insurance cases and fo r research purposes.
If neu rological symptoms are pr esent , an electroneurographic examination (measurement of motor and sens or y conduction velocities and sensory amplitudes in the med ian and ulnar nerves on both sides) is essential since carpa l tunnel synd ro m e, a tr eat able co nd ition , is co m m o n in vibratio n-exposed gro ups . The measu rem ent of sens o ry th resh olds m ight be used as complement ary examinations. Until mo re is know n o f th e pathophysiological mechanism beh ind th e sym ptoms of the vibra tion synd ro me , th e patient's description of sym pto ms , combined with a det ailed exp osure history, will remain essential fo r the di agnosisirr esp ecti ve of the results o f the test s used . A patient who has a typi cal history of Ra ynaud' s ph en om enon and/ or pare sthesias and ha s been expos ed to hand-arm vibra tio n dail y for man y yea rs, when no other rea son for the sym pto ms ca n be found , mu st be co ns ide red as ha ving vibra tio n synd ro me. I. Abbru zzese M, Loeb C, Ratto S, Sacco G. A comparative electrophysiological and histological study of sensory conduction velocity and Meissner corpuscles of the median nerve in pneumatic tool workers. Eur Neurol 16 (1977) 106-114.