The influence of brushing force and stroking velocity on dynamic mechanical allodynia in patients with peripheral neuropathy.

Recently we demonstrated brush-evoked allodynia to be a partially graded phenomenon since increased brushing length and number of strokes significantly increased the brush-evoked pain intensity. In this study the influence of stroking velocity and brushing force on dynamic mechanical allodynia was examined in 16 patients with peripheral neuropathy. Brush-evoked allodynia was induced by lightly stroking 60mm of the skin twice with a 16 mm wide brush while varying stroking velocity (10, 20, 30 mm/s) and brushing force (10, 20, 40 g). Intensity and duration of brush-evoked allodynia was recorded using a computerized visual analogue scale. The total brush-evoked pain intensity, including painful aftersensation was calculated as the area under the curve. Significantly increased total brush-evoked pain intensity was demonstrated with lower stroking velocity (P<0.001) and higher brushing force (P<0.05). Higher maximum pain intensity was reported with higher brushing force. In conclusion, our findings demonstrated a significant relationship between the total brush-evoked pain intensity and stroking velocity as well as brushing force. Together with previously accumulated data these results substantiate the usefulness of this semi-quantitative assessment method in longitudinal studies on dynamic mechanical allodynia.