Normal values for sensory thresholds in the cervical dermatomes - A critical note on the use of Semmes-Weinstein monofilaments

In many healthy subjects, sensory thresholds for touch using Semmes-Weinste in monofilaments appear to be higher than the 2.83 filament, which some aut hors have suggested as a screening instrument. The currently proposed norma l values, the interpretation of results, as well as the calibration of the filaments are questioned. A normative study of 20 normal subjects using Sem mes-Weinstein monofilaments was undertaken at a pain clinic in a university hospital. The main outcome measures were sensory thresholds (touch) in der matomes C3 to C8. Per subject, 24 sites were tested and 50 sites in dermato me C5 left of one subject. The threshold distribution patterns were analyze d. The mean threshold expressed in log (10 x F;with F = force in milligrams ) of all sites (n = 480) in normal subjects was 3.10 (95% confidence interv al, 2.34-3.86). The mean threshold per subject was 3.10 (range, 2.70-3.50). The mean threshold of 50 sites in dermatome C5 left of one healthy subject was 3.22 (range, 2.42-4.02). In the study contained herein, sensory thresh olds in the cervical dermatomes have been shown to be higher than the gener ally proposed normal values. The cervical dermatomes show thresholds from 0 .13 to 8.47 mN. This concurs with other authors. Results depend on the test ing method, which in this study was different from previous studies. The te sting method must be described accurately. The distribution of thresholds w ithin all tested sites, dermatomes, subjects, or even within one dermatome in one subject are comparable. Individual results have to be related to the mean of the subject to determine abnormality. Calibration of the monofilam ents is important. When these terms are met, testing with Semmes-Weinstein monofilaments is an easy, reliable, and relatively inexpensive method of qu antitative sensory testing and can be a useful tool in the process of rehab ilitation.