ORIGINAL RESEARCH Carpal Tunnel Syndrome Diagnostic Usefulness of Ultrasound Measurement of the Median Nerve Area and Quantitative Elastographic Measurement of the Median Nerve Stiffness Luz Moran, MD, PhD , Ana Royuela, PhD, Alberto Perez de Vargas, MD, Ana Lopez, MD, Yamilet Cepeda, MD, Gianluca Martinelli, MD Objectives—To correlate the ultrasound (US) measurements of the median nerve cross-sectional area (CSA) and the measurements of its stiffness by shear wave elastography (SWE) with the severity grade of carpal tunnel syndrome (CTS) using electrodiagnostic testing (EDT) and to determine the cutoff points for CSA and SWE measurements to allow us to discriminate patients with mod- erate and severe CTS from those with mild or negative EDT findings. Methods—Seventy-three patients with 105 hands with a clinical suspicion of CTS were studied with US and SWE. We measured the median nerve CSA and elastic- ity (E) at the tunnel inlet (CSAu and Eu), in the quadratus pronator (CSAo and Eo), and the differences (CSAu – CSAo and Eu – Eo). Results—The nerve area and stiffness increased according to the EDT severity of CTS; the CSA increased proportionally as CTS increased from negative to severe according to EDT, and the stiffness was not different between patients with nega- tive and mild EDT findings but was higher in patients with moderate and severe EDT findings versus negative and mild EDT findings. The cutoff points of a CSAu of 14 mm 2 or greater and an Eu – Eo of 57 kPa or greater together allowed the discrimination of moderate and severe CTS from the rest. Conclusions—The joint use of US and SWE is an alternative to EDT in the clini- cal management and treatment of patients with a clinical suspicion of CTS. Key Words—carpal tunnel syndrome; elastography; median nerve; ultrasound C arpal tunnel syndrome (CTS) is the most common compressive peripheral neuropathy. The diagnosis of CTS is based on the clinical history and physical examination findings. 1 Although there is no reference standard, electrodiagnostic testing (EDT) has often been used to confirm the grade and severity of CTS. However, the limitations of EDT are that this procedure is uncomfortable for the patient and has a false-negative rate between 16% and 34%. 2,3 Ultrasound (US) has emerged as a useful tool in the study of CTS. B-mode US is fast, has a reduced economic cost, and is not uncomfortable for the patient. 4–15 A meta-analysis of 38 studies with 3995 wrists concluded that the best US diagnostic criterion is enlargement of the median nerve (MN) cross-sectional area (CSA) at the tunnel inlet, with sensitivity of 87% and specificity of 83%. 16 However, measurement of the CSA is limited by interindividual Received March 13, 2019, from the Departments of Radiology (L.M., Y.C., G.M.), Statistics (A.R.), Neurophysiology (A.P.d.V.), and Rehabilitation (A.L.), Hospital Universi- tario Puerta de Hierro, Majadahonda, Madrid, Spain. Manuscript accepted for publication July 7, 2019. We thank the patients who agreed to participate voluntarily in this study and Gonzalez Hernando C, MD, PhD, head of the Department of Radiology of the Hospital Universitario Puerta de Hierro, for providing us the opportunity to do this project. All of the authors of this article have reported no disclosures. Address correspondence to Luz Moran, MD, PhD, Department of Radiology, Hospi- tal Universitario Puerta de Hierro, Majada- honda, Madrid, Spain. E-mail: lmoran.moran6@gmail.com Abbreviations AUC, area under the curve; CSA, cross- sectional area; CSAo, cross-sectional area in the quadratus pronator; CSAu, cross- sectional area at the tunnel inlet; CTS, carpal tunnel syndrome; E, elasticity; EDT, electro- diagnostic testing; Eo, elasticity in the quad- ratus pronator; Eu, elasticity at the tunnel inlet; MN, median nerve; ROI, region of interest; SWE, shear wave elastography; US, ultrasound doi:10.1002/jum.15111 © 2019 by the American Institute of Ultrasound in Medicine | J Ultrasound Med 2019; 9999:1–9 | 0278-4297 | www.aium.org