Vibrometry testing for carpal tunnel syndrome: a longitudinal study of daily variations.

The method of limits procedure was used to obtain 84 120Hz vibration thresholds, over a 3-month period, on four age-matched women with different levels of carpal tunnel syndrome (CTS). Each woman used a keyboard for 4 hours a day during work. Testing was conducted in a room with a temperature of 28 degrees C +/- 2 degrees C after 20 minutes acclimation. Results indicate vibration thresholds vary significantly from day to day and also demonstrate how a single vibrometry measure may falsely identify the participant's true CTS condition. Specifically, a single measure could account for a negative CTS determinations in affected wrists or positive CTS determinations in healthy wrists. Subsequent analysis revealed menses related fluid retention and day of the week increase the vibration thresholds. Analyzing the levels of fluid retention by day of the week indicates a compounding effect of the personal and occupational risk factors.

Use of motor nerve conduction testing and vibration sensitivity testing as screening tools for carpal tunnel syndrome in industry.

Increased attention to carpal tunnel syndrome in industry has resulted in the development of several proposed screening tests. This investigation evaluated the use of two portable devices for measuring motor nerve conduction time and tactile sensitivity to 120 Hz vibration in a field setting. Forty-seven control participants, 63 manufacturing plant workers with and without symptoms of carpal tunnel syndrome, and 22 patients with physician-diagnosed carpal tunnel syndrome were tested with the NervePace electroneurometer and the Vibration II vibration threshold measurement device. Nerve conduction time differed significantly between the controls, the asymptomatic workers, and the participants with carpal tunnel syndrome or symptoms of carpal tunnel syndrome. The vibration threshold was higher in the carpal tunnel syndrome group than in the other groups; however, further examination of the data revealed no differences in threshold unless nerve conduction time exceeded the control mean by at least three standard deviations. The false-negative rates associated with the tests limit their usefulness in screening for carpal tunnel syndrome.