PO 284 Evaluating the diagnostic accuracy of ultrasound compared to nerve conduction studies in carpal tunnel syndrome

Abstract

Introduction/Background: Nerve conduction studies (NCS) and ultrasound (USS) are widely used modalities for evaluating carpal tunnel syndrome (CTS). While often considered complementary, their comparative diagnostic accuracy remains an area of ongoing research. This study aims to evaluate the diagnostic accuracy of USS, in relation to NCS, in patients with suspected CTS. Method(s): We retrospectively analysed data from 485 patients who underwent NCS over a six-month period (August 2024 - January 2025). Patients were identified who underwent both NCS and USS for suspected CTS. Nerve conduction studies were performed in accordance with AANEM guidelines, and the Canterbury scale was used to assess the severity. Ultrasound was considered positive if sonographers identified median nerve abnormalities, such as increased cross-sectional area. Sensitivity and specificity of ultrasound were calculated in relation to neurophysiological findings. Result(s): A total of 187 patients were diagnosed with CTS based on nerve conduction studies. A subset of 62 patients (94 wrists) underwent assessment by both NCS and USS, comprising 63 wrists with NCS-confirmed CTS and 31 wrists with negative NCS findings. Among the 63 NCS-positive CTS wrists, 25 were also positive for CTS on ultrasound, while 38 were negative. Of the 31 NCS-negative wrists screened with ultrasound, 3 showed abnormal sonographic findings, characterised by hypoechogenic or bifid median nerves, and 28 were negative. Ultrasound demonstrated a sensitivity of 39.7 % and a specificity of 90.3 % for diagnosing CTS relative to NCS. However, the low sensitivity of USS was mainly observed in very mild or mild CTS cases (Canterbury grades 1 and 2, respectively). Conclusion(s): Our findings show that a significant proportion of patients with neurophysiologically confirmed early-stage CTS had normal USS results, suggesting that USS alone may have lower sensitivity. This reinforces the role of nerve conduction studies as the primary diagnostic tool. However, the high specificity of ultrasound and its ability to identify musculoskeletal mimics highlight the value of combining both modalities to improve the diagnostic accuracy. Further research is needed to explore the correlation between CTS severity and sonographic changes. Copyright © 2025