Diagnostic accuracy of ultrasound in carpal tunnel syndrome: analysis of established and novel parameters

OBJECTIVES: This study evaluated the diagnostic accuracy of 3 ultrasound-based parameters-median nerve cross-sectional area (CSA), elasticity (E value), and blood flow pixel ratio (BFPR)-in grading carpal tunnel syndrome (CTS) severity. These parameters were assessed using high-frequency ultrasound, shear wave elastography (SWE), and superb microvascular imaging (SMI), with nerve conduction studies (NCS) as the reference standard. METHODS: A prospective study conducted between April 2024 and January 2025 included 128 patients with suspected CTS and 25 healthy controls, totalling 223 median nerves. CTS severity was categorized as mild, moderate, or severe based on NCS results. RESULTS: CSA increased from 10.05 mm2 in controls to 17.35 mm2 in severe CTS, E value rose from 42.35 kPa to 128.39 kPa, and BFPR increased from 3.99% to 19.76%. BFPR had the highest sensitivity for detecting mild CTS (cut-off 5.9%). Significant correlations (r > 0.78, P < .0001) were found among CSA, E value, and BFPR. ROC analysis showed excellent diagnostic accuracy with AUC values of 0.90-0.97 for distinguishing controls from CTS patients and 0.93-0.95 for differentiating mild from moderate-to-severe CTS. CONCLUSION: Multiparametric ultrasound, particularly BFPR via SMI, provides a reliable, non-invasive alternative to NCS for early CTS detection and severity grading, with potential for standardizing diagnostic guidelines. ADVANCEMENT IN KNOWLEDGE: This study improves ultrasound-based CTS diagnosis by integrating CSA, E value, and BFPR, offering an effective method for early detection and severity grading. BFPR, especially via SMI, demonstrates high sensitivity for mild CTS and could standardize diagnostic approaches.