Thresholds for the perception of pressure, sharpness, and mechanically evoked cutaneous pain: effects of laterality and repeated testing.

Twenty-four healthy human subjects provided thresholds for their perception of pressure, sharpness, and pain. Mechanical forces were applied to the dorsal surface of the digits with flat-tipped probes of various sizes. Thresholds (expressed as force) increased with increasing probe size, as previously described. There was no evidence of a laterality difference for any of the thresholds. There was a trend for increasing thresholds with repeated testing, but this trend was not statistically significant for the group as a whole. Examination of individual subjects' thresholds over time revealed that 27% showed significant increases in pain threshold over the 15 days of testing. In contrast, only 6% of subjects showed significant increases in sharpness or pressure thresholds over the same period. Thus, whereas most subjects exhibited stable pain thresholds, approximately one-fourth showed significant increases in pain threshold over time. We conclude that for evaluating regional dysesthesia or hemidysesthesia, a right-left difference in pain thresholds will provide a more sensitive and reliable measure than absolute pain threshold.