Ethnic differences regarding sensory, pain, and reflex responses in the trigeminal region

Objective: The present study evaluated ethnic differences in sensory, pain responses, and the exteroceptive suppression reflex (ES) in the trigeminal region. Methods: Twenty-eight Caucasian (14 men and 14 women, age from 20 to 31) and 28 gender and age matched Japanese participated. Tactile detection thresholds and filament-prick pain detection thresholds were measured on the left cheek skin. Surface EMG was recorded from the left masseter muscle, and 13 different intensities of electrical stimuli were applied to the skin overlying the left mental nerve. The first stimulation intensity at which the late ES appeared was defined as the electrical reflex threshold. The duration and suppression degree of the ES were also determined. Results: Japanese subjects had a significantly lower sensory and pain threshold then Caucasian subjects. Caucasian subjects had a significantly lower electrical reflex threshold in comparison to Japanese subjects. Caucasian subjects had significantly longer duration of the ES and larger suppression degree of the ES compared to Japanese subjects. Conclusions: Our results demonstrate that ethnic differences exist not only concerning sensory and pain responses but also regarding reflex (motor) responses. Significance: The findings of this study have direct implications for studies evaluating different types of orofacial pain conditions and trigeminal reflexes. (C) 2008 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.