Ultrasonographic Study of Median Nerve according to Changed Wrist Position

ABSTRACT

OBJECTIVE: To compare the diagnostic value between Phalen's test and reverse Phalen's test using a morphological change of the median nerve and the carpal tunnel seen by high-resolution ultrasonography and to research on an ultrasonography as an available tool for the screening and follow up aid-test of the carpal tunnel syndrome (CTS). METHOD: A cross-sectional area and a flattening ratio of the median nerve, and a cross-sectional area of the carpal tunnel were measured in neutral, maximally flexed (Phalen's test), and maximally extended (reverse Phalen's test) positions in 59 wrists of 30 normal subjects. RESULT: The cross-sectional area of median nerve was significantly decreased in maximal flexion (p<0.01), and in maximal extension (p<0.01). The mean flattening ratio of median nerve was revealed significant change in maximal flexion (p<0.01), and in maximal extension (p<0.01). The mean cross-sectional area of the carpal tunnel was significantly decreased in maximal flexion (p<0.01), and in maximal extension (p<0.01), with comparing to neutral position, respectively. CONCLUSION: Phalen's test reveals higher degree of irritation to median nerve. The high-resolution ultrasonography is suggested as an available tool for the screening and follow up aid-test for the CTS.