Quantitative test for sensory hand symptoms based on mechanoreceptor-specific vibrotactile thresholds

Abstract

A vibrotactile test for assessing the presence or absence of sensory symptoms in the hand has been developed from thresholds believed mediated by Merkel disks and Meissner corpuscles at the fingertips. It is constructed from the summed differences between the thresholds recorded at the fingertip of an individual and the mean values of the threshold for healthy persons at the same stimulation frequencies. The summed normalized threshold shift, TS(Sum(SD)), is shown to be related to reports by subjects of numbness and pain using three statistical tests for evaluating the significance of associations in 2x2 contingency tables. The small number of subjects (15) restricts direct calculation of a fence value for TS(Sum(SD)), t, between the presence and absence of symptoms: accordingly, interpolation between calculated t values has been performed graphically. A common range of t values can be identified that is judged significantly by each statistical test (3.3<or=t<3.9 for numbness; 3.6<or=t<4.1 for pain). The range encompasses the boundary previously identified between "normal" and "abnormal" vibrotactile thresholds, that is, thresholds for which the (two-sided) probability of occurrence in the hands of healthy persons is p approximately 0.05.