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Does Ultrasonography, In Conjunction with Nerve Conduction Study, Plays Any Role in The Diagnosis and The Evaluation of Severity in Patients with Clinically Diagnosed Carpal Tunnel Syndrome? A Prospective Study

Christina Angelopoulou, Ioannis Chrysafis, Anthimos Keskinis, Konstantinos Tilkeridis, Grigorios Trypsianis, Konstantinos Paraskevopoulos, Georgios Drosos, Athanasios Ververidis

Category: Clinical Research

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Background: Although nerve conduction study (NCS) represents the commonly performed test to functionally confirm the presence of carpal tunnel syndrome (CTS) in the daily clinical practice, the value of ultrasonography (U/S) is well established as a diagnostic tool for structural evaluation of CTS. Τhe purpose of this study was to compare U/S and nerve conduction velocity in patients with clinically diagnosed CTS, for assessing the usefulness of U/S in determining CTS severity.

Material and Methods: A cross-sectional study with prospective data collection was carried out. 71 patients (100 hands) with clinically diagnosed idiopathic CTS were included in this study. Τhe protocol was comprised of a NCS and an U/S where the cross sectional area (CSA) and the flattening ratio (FR) of the median nerve at the carpal tunnel inlet (level of the pisiform) were measured.

Results: In 94 hands (65 patients) out of 100 hands (71 patients), CTS was electrophysiologically confirmed. The CSA increase of the median nerve was proportional to the electrophysiological severity of the CTS. ROC analysis demonstrated good diagnostic value in both CSA and FR (CSA: AUC = 0.974, p<0.001, FR: AUC = 0.928, p <0.001). The CSA at the tunnel inlet with a threshold of 10.5 mm2 had the best diagnostic accuracy with a sensitivity of 94.7% and a specificity of 92.5%, as well as the FR with a threshold of 3.1 had the best diagnostic accuracy with a sensitivity and a specificity of 78.7% and 98.8%, respectively. Furthermore, ROC curve analysis for CTS electrophysiological severity showed a superior performance of the CSA (AUC=0.911, p<0.001) compared to the FR (AUC=0.647, p=0.023). The optimal cut-off point of 15.5 mm2 for CSA at the carpal tunnel inlet was defined to determine severe CTS, which yielded a sensitivity of 82.8% and a specificity of 92.3%. Conclusions: The U/S of the median nerve combined with electrodiagnostic study, increases significantly the sensitivity and reliability of the patient's diagnostic approach suffering from CTS. It can also be used for the assessment of CTS severity, replacing NCS, as its benefits such as low cost, non-invasive procedure, less time and patient’s convenience are remarkable.

Keywords: Carpal Tunnel Syndrome, Nerve Conduction Study, Ultrasonography, Electrodiagnostic Study, Cross Sectional Area, Flattening Ratio, Median Nerve


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