Assessment of impaired tactile sensation. A pilot study

Three methods are compared for assessing impaired tactile sensation in vibration-exposed workers: a medical examination including traditional neurological tests and refined measures of vibrotactile perception and gap detection. Of 18 subjects only 12 were judged free of confounding factors--five forestry workers exposed to chain-saw vibration, aged 28 (SD 5) years, and seven laboratory workers not exposed to vibration, aged 36 (SD 7) years. Each method identified the same subject as suffering the most from tactile impairment, but they differed in their ranking of the severity of sensory changes. The ranking by gap detection and vibrotactile perception at low frequencies was the most consistent [Spearman rank correlation coefficient (r) = 0.90]. The clinical results, when staged according to the neurological component of vibration-induced white finger, ranked the thresholds for gap detection and low-frequency vibrotactile perception equally well (r = 0.70). In contrast, the Taylor-Pelmear staging of the clinical results poorly represented the ranking of tactile thresholds recorded for these workers (r = 0.00 and -0.20, respectively). It also appeared that improved techniques for measuring vibrotactile and gap perception thresholds can detect sensory changes in the fingers not consistently found by conventional clinical tests.