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Journal of Occupational & Environmental Medicine:
Letters To The Editor

Screening for Carpal Tunnel Syndrome in the Workplace

Nathan, Peter A. MD; Keniston, Richard C. MD; Meadows, Kenneth D. PT; Lockwood, Richard S. BSc

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Portland Hand Surgery and Rehabilitation Center; Portland, OR

To the Editor: Pransky et al1 stated that effective workplace screening for carpal tunnel syndrome (CTS) requires tests with high sensitivity and reasonable specificity. These tests should be able to detect increased risk for CTS in asymptomatic individuals.2 These standards exclude use of a portable electrodiagnostic testing device (such as NERVEPACE or Neurosentinel), motor nerve conduction studies (NCS), long segment sensory NCS, symptom questionnaires, and hand symptom diagrams, as none of these has the requisite sensitivity.1,3-10 Symptom questionnaires also lack the requisite specificity.2,6,8,9,11

In long-term follow-up studies, we have found formal NCS results to be much more stable and reliable than self-reported symptoms.6,8,9 Symptoms that were not supported by NCS abnormalities tended to be especially labile.6,8,9,11 The most sensitive and efficient tests for predicting future specific hand/wrist symptoms and CTS were short-segment sensory studies, the 8-cm sensory latency and particularly the maximum latency difference(MLD),5,6,8,9 based on the palmar segmental centimetric ("inching") technique of Kimura.12 In 464 initially asymptomatic worker hands, after 11 years, the MLD gave an odds ratio of 20:1 for predicting de novo CTS comparing hands with an initial MLD of ≥ 0.52 ms to hands with an initial MLD of < 0.28 ms.9

In a cost-benefit analysis of applying early detection methods for the purpose of reducing CTS-related costs, neither portable testing device results nor symptom questionnaires will provide long-term benefit. We feel the extra cost and time involved in performing formal NCS in the industrial setting are more than justified by the objective results. Formal NCS are valid, stable and reproducible even after long time intervals, and reliable if done with standard NCS techniques.5-9,12 In our experience, precise functional measurement of the median nerve within the carpal tunnel, in short segments, is the most reliable predictor of future hand/wrist symptoms and CTS in industrial workers and meets the criteria for providing high sensitivity and reasonable specificity.6-9

Peter A. Nathan, MD

Richard C. Keniston, MD

Kenneth D. Meadows, PT

Richard S. Lockwood, BSc

Portland Hand Surgery and Rehabilitation Center; Portland, OR

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References

1. Pransky G, Long R, Hammer K, Schulz LA, Himmelstein J, Fowke J. Screening for carpal tunnel syndrome in the workplace: an analysis of portable nerve conduction devices. J Occup Environ Med. 1997;39:727-733.

2. Bingham RC, Rosecrance JC, Cook TM. Prevalence of abnormal median nerve conduction in applicants for industrial jobs. Am J Ind Med. 1996;30:355-361.

3. Chaudhry V. Technology review: NervePace digital electroneurometer. Muscle Nerve. 1997;20:1200-1203.

4. Wolens D. The predictive ability of instrumentation for screening and surveillance of carpal tunnel syndrome. In: Kasdan MS, ed.Occupational Hand and Upper Extremity Injuries and Diseases, 2nd edition. Philadelphia: Hanley & Belfus; 1997:141-148.

5. Jablecki CK, Andary MT, So YT, Wilkins DE, Williams FH. Literature review of the usefulness of nerve conduction studies and electromyography for the evaluation of patients with carpal tunnel syndrome.Muscle Nerve. 1993;16:1392-1414.

6. Nathan PA, Keniston RC, Meadows KD, Lockwood RS. Predictive value of nerve conduction measurements at the carpal tunnel.Muscle Nerve. 1993;16:1377-1382.

7. Nathan PA, Keniston RC, Meadows KD, Lockwood RS. Electrodiagnostic testing in hand surgery. J Hand Surg [Am]. 1997;22:948-949.

8. Nathan PA, Keniston RC, Myers LD, Meadows KD. Longitudinal study of median nerve sensory conduction in industry: relationship to age, gender, hand dominance, occupational hand use, and clinical diagnosis. J Hand Surg [Am]. 1992;17:850-857.

9. Nathan PA, Keniston RC, Meadows KD, Lockwood RS. Predictive value of nerve conduction studies. Occup Environ Med. In Press.

10. Verbrugge LM, Ascione FJ. Exploring the iceberg: common symptoms and how people care for them. Med Care. 1987;25:539-569.

11. Silverstein BA, Fine LJ, Stetson D. Handwrist disorders among investment casing plant workers. J Hand Surg [Am]. 1987;12:838-844.

12. Kimura J. The carpal tunnel syndrome: localization of conduction abnormality within the distal segment of the median nerve.Brain. 1979;102:619-635.

Editor's Note: Dr Pransky chose not to reply.

© Williams & Wilkins 1998. All Rights Reserved.

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