SPATIAL AND GENDER-DEPENDENT VARIATIONS IN PERIORAL PINPRICK SENSITIVITY

Twenty-eight right-handed young adults participated in a sensory testi ng experiment to evaluate pinprick sensitivity at ten spatially matche d sites on the right and left sides of the face. Stimuli were provided by a sharp-pointed dental explorer on which a rubber eraser had been positioned to minimize variations in the extent to which the skin was indented. Sharpness was defined as the magnitude at which abrupt, loca lized pricking/stinging sensations were evoked. A magnitude matching p rocedure was used to reduce among-subject variability in the data. Spe cifically, each estimate of sharpness was adjusted (i.e., divided) by the subject's mean estimate of the brightness of a visual stimulus. Pr ior to data collection, subjects were carefully instructed on the use of a common numerical scale for assignment of values of sharpness and brightness. Repeated-measures analysis of variance of the adjusted est imates of sharpness revealed a non-significant effect of gender (p > 0 .4), a highly significant effect of side (p < 0.0001), and a highly si gnificant effect of test site (p < 0.0001). Pinprick percepts were sha rper on the left side of the face than on the right. Moreover, the ver milion of the upper lip exhibited the greatest sensitivity to pinprick ; the vermilion of the lower lip exhibited the least sensitivity. Thes e results suggest that use of a patient's sensitivity to pinprick duri ng clinical neurosensory examination must be undertaken in an informed manner. A conclusion of pathological alteration in sensation can be m ade only after consideration of the normal spatial variations in the p ercept of sharpness.