Sonography in the diagnosis of carpal tunnel syndrome: a critical review of the literature.

Advances in ultrasound technology have made it possible to gain higher spatial resolution and even depict nerves with excellent visual quality. In this article, the literature concerning sonography in the diagnosis of carpal tunnel syndrome (CTS) is critically reviewed. We searched Medline for studies on sonography in the diagnosis of CTS and used the reference lists of the articles found. A total of seven studies on the diagnostic capabilities of sonography was found. There were considerable differences in study design. A reliable diagnosis of CTS could be made sonographically, mainly based on an increase in cross-sectional area of the median nerve at the level of the pisiform or hamate bone. However, most studies could not compare the diagnostic capabilities of sonography to those of electrodiagnostic studies, because the latter was applied as the gold standard. Several other reports on the possible extra value of sonography in CTS are mentioned (mass lesions, anatomical variants, rheumatological diseases, renal dialysis-related amyloidosis, surgery, corticosteroid injection). It is probable that sonography will not replace electrodiagnostic studies, but may serve as an additional investigation. To gain further insight into the possible additional value of sonography, it is necessary to examine subcategories of CTS patients in which electrodiagnostic studies are equivocal.