In diagnosis of carpal tunnel syndrome, there are many techniques with high sensitivity. Among them, the median-radial latency difference(MRLD) is one of the most useful technique in screening mild carpal tunnel syndrome with high sensitivity, no painful discomfort to patients and no motor artifact.
In this study, we examined the effect of the thumb position(radial abduction and adduction) on the MRLD. Because the stimulation sites of the median sensory and superficial radial nerves are different from each other, the free movement of the thumb in this examination is not avoidable.
The results are 1) there is no significant effect of the thumb position on median sensory latency. 2) There is no significant effect of the thumb position on superficial radial latency. 3) There is significant effect of the thumb position on MRLD(P<0.01). Therefore, if we diagnose the mild carpal tunnel syndrome with MRLD, the thumb position must be maintained in neutral position through the examination.
