The effect of a standard activity on the size of the median nerve as determined by ultrasound visualization

The purpose of this study was to determine whether a standardized hand acti vity would produce changes in the cross-sectional diameter of the median ne rve. Ultrasound measures of proven reliability of the cross-sectional diame ter of the median nerve in the wrist were taken. These measures were taken before activity and immediately after the activity, after 5 minutes, and af ter 10 minutes. The median nerves of 40 normal subjects showed an increase in cross-sectional diameter immediately after hand activity then returned t o a size close to the preactivity size within 10 minutes. The cross-section al area of the carpal canal did not change significantly after the hand act ivity was performed. Female gender and body mass index over 25 were associa ted with significantly larger size increases in the median nerve. This prel iminary study suggests that ultrasound is sensitive to the effects of activ ity upon the hand. Copyright (C) 2001 by the American Society for Surgery o f the Hand.