The transverse scan view of an ultrasound image of the median nerve obtained at the level of the wrist crease.

<p>The trace of the hypoechoic boundary of median nerve (A) denotes cross-sectional area of median nerve. The flattening ratio of median nerve is calculated by the ratio of B/C, where (B) denotes the major axis length and (C) denotes the minor axis length of median nerve.