Local vibrotactile and pain sensitivities are negatively related in temporomandibular disorders

Earlier research has shown that cutaneous experimental pain can elevate the vibrotactile threshold at the same skin locus. The purpose of this study was to determine whether vibrotactile and pain thresholds in a clinical (temporomandibular disorders [TMD]) population are consistent with the hypothesis that chronic pain causes a similar elevation. Specifically, we predicted that TMD subjects with soreness (low palpation-pain threshold) at a given skin site would have relatively high vibrotactile thresholds at the same location. Measurements on the skin overlying the masseter in 18 individuals with TMD showed that pain sensitivity was negatively correlated with sensitivity to 20-Hz vibration (presumed to activate a rapidly adapting mechanoreceptive channel), but not with sensitivity to 200-Hz vibration (thought to activate primarily a slowly adapting channel, because the Pacinian channel is lacking in the orofacial region). There was no relationship between vibration thresholds over the masseter and pain threshold at other orofacial sites, including the contralateral masseter. Vibrotactile and pain thresholds were uncorrelated in control participants without chronic pain (n = 18). The results indicate that in TMD, a localized relationship exists between pain sensitivity and the sensitivity of a low-frequency vibrotactile channel.