Ultrasonographic Study of Median Nerve According to Changed Wrist Position in Diabetics and Normal Subjects

ABSTRACT

BACKGROUND: 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 in diabetics and normal controls 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). METHODS: 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 controls and 60 wrists of 30 diabetics. RESULTS: 1) In controls and diabetics, the mean cross-sectional area of median nerve at the hamatum were 8.8/10.2 mm2, 8.0/9.5 mm2, 8.3/9.4 mm2, the mean flattening ratio were 3.0/3.0 mm2, 2.4/2.0 mm2, 3.2/3.0 mm2, the mean cross-sectional area of carpal tunnel were 176.5/197.7 mm2, 157.9/187.0 mm2, 170.6/192.5 mm2 in neutral, maximal flexion and maximal extension. 2) In controls, the cross-sectional area of median nerve and carpal tunnel were significantly decreased in maximal flexion(p<0.01), and in maximal extension(p<0.01). 3) In controls, the mean flattening ratio of median nerve was revealed significant change in maximal flexion(p<0.01), and in maximal extension(p<0.01). 4) In diabetics, the flattening ratio was significantly decreased in maximal flexion(p<0.01) with com- paring to neutral position. 5) In diabetics, the cross-sectional area of median nerve and carpal tunnel were significantly increased in all positions(p<0.05), and the mean flattening ratio of median nerve was similar to controls. CONCLUSION: In diabetics, increased cross-sectional area of median nerve can be explained by swelling of median nerve, also increased cross-sectional area of carpal tunnel is can be said to have taken place by the decreasing of the useful space in between the median nerve and carpal tunnel, this show that the diabetics have the high risk of the CTS. 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