Diagnostic utility of median nerve CSA to ulnar nerve CSA ratio in the diagnosis of mild idiopathic carpal tunnel syndrome

Abstract

Abstract Background Ultrasonography (US) measurement of median nerve cross-sectional area (m-CSA) at pisiform is increasingly utilized in identification of carpal tunnel syndrome (CTS), but there is still no agreement about the ideal cut-off value to employ. The aim of the study was to explore whether the median CSA to ulnar CSA ratio at the level of pisiform may yield a more accurate diagnosis of CTS. The study included 50 patients with mild idiopathic CTS (ICTS), assessed clinically and by nerve conduction studies, and 50 matched controls. M-CSA, median nerve flattening ratio and swelling ratio (m-SR), palmer bowing, and median CSA to ulnar CSA ratio (m-CAS:u-CSA) were measured for patients and controls. The cutoff values for the US parameters for the diagnosis of ICTS were evaluated. Results Compared to the control group, the ICTS group had significantly higher m-CSA (p < 0.001), higher m-CSA:u-CSA ratio (p < 0.001), higher m-SR (p = 0.012, and higher palmar bowing (p < 0.001). Use of m-CSA cutoff value of 11.78 mm2 and CSA:u-CSA ratio cut-off point of 2.97 yielded the greatest sensitivity and specificity for the diagnosis of ICTS. Conclusion The m-CSA:u-CSA ratio is slightly superior to the m-CSA in the diagnosis of CTS in terms of sensitivity and specificity.

Keywords

• Carpal tunnel syndrome
• Median nerve cross-sectional area
• Median to ulnar ratio