• Ahad Azami, Nasrollah Maleki, Hassan Anari, Manouchehr Iranparvar Alamdari, Mohammadreza Kalantarhormozi, and Zahra Tavosi.
• Department of Internal Medicine, Imam Khomeini Hospital, Ardabil University of Medical Sciences, Ardabil, Iran.
• Int J Rheum Dis. 2014 Jul 1; 17 (6): 612-20.

ObjectiveCarpal tunnel syndrome (CTS) is the most common form of peripheral entrapment neuropathy. The use of sonography for investigation and diagnosis of musculoskeletal conditions has been rapidly increasing over the past few decades. The purpose of this study was to determine whether sonography can be an alternative method to nerve conduction study (NCS) in the diagnosis of CTS.MethodsIndividuals with electrodiagnostically proven CTS and healthy control subjects were enrolled prospectively. Median nerve cross-sectional area (CSA) and flattening ratio (FR) at three different levels, proximal to tunnel inlet, at tunnel inlet and tunnel outlet, and flexor retinaculum thickness, were measured. Then, comparisons between ultrasonography and NCS were made.ResultsWe assessed 180 wrists, of which 120 were electrophysiologically confirmed as CTS diseased hands and 60 nondiseased hands in 90 patients (83 women and seven men). The mean median nerve CSA at the tunnel inlet was 13.31 ± 3.23 mm(2) in CTS diseased hands and 8.57 ± 0.82 mm(2) in nondiseased hands. Post hoc comparisons between the diseased and nondiseased hands demonstrated that the CSA at various levels of the median nerve were significantly greater in the CTS diseased hands than the nondiseased hands (P = 0.001). CSA at the tunnel inlet with a threshold of 9.15 mm(2) gave the best diagnostic accuracy with a sensitivity and specificity of 99.2% and 88.3%, respectively. The difference in cross-sectional area of the median nerve in mild, moderate and severe CTS was statistically significant.ConclusionUltrasonographic measurement of the CSA of the median nerve at the carpal tunnel inlet is useful in diagnosing and grading CTS.© 2014 Asia Pacific League of Associations for Rheumatology and Wiley Publishing Asia Pty Ltd.

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