Median nerve ultrasonography in carpal tunnel syndrome: findings from two laboratories.

Ultrasonographic (US) enlargement of the median nerve at the wrist is known to be consistent with carpal tunnel syndrome (CTS), although the effects of different measurement techniques, equipment, and patient populations remain unknown. The purpose of this study was to examine the similarities and differences of US findings in CTS between two electromyography (EMG) laboratories. In 2006 and 2007, US measurements of the median nerve were recorded independently and statistically analyzed in patients with CTS at two EMG laboratories (Duke University, Durham, NC, USA, and Università Cattolica del Sacro Cuore, Rome, Italy). Patient age, median nerve area in the forearm, and neurophysiologic score did not differ significantly between the two laboratories. The North Carolina group had a larger median nerve area at the wrist and wrist-to-forearm ratio than the Italian group, although both were elevated in reference to established values for the diagnosis of CTS. Median nerve US is less susceptible to differences between laboratories than previously thought, permitting greater generalization of findings.