Abstract
BackgroundUltrasonography (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.ResultsCompared 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.ConclusionThe m-CSA:u-CSA ratio is slightly superior to the m-CSA in the diagnosis of CTS in terms of sensitivity and specificity.
Highlights
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
idiopathic CTS (ICTS) patients had a significantly higher m-CSA pisiform than the controls, which is in agreement with the findings reported by previous studies [6, 17, 18]
The results of the present study showed that m-CSA and m-CSA:u-CSA ratio were significantly correlated with median nerve distal motor latency, Compound muscle action potential (CMAP), sensory latency, and sensory amplitude, albeit that m-CSA:ulnar CSA (uCSA) ratio had stronger correlation than m-CSA with all median nerve Electro-diagnostic testing (EDX) parameters
Summary
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. Diagnosis of CTS is largely based on clinical findings and electro-diagnostic (EDX) testing [2]. CTS is the most common reason for referral to electro-diagnostic (EDX) testing. EDX testing has its own limitations: it does not allow visualization of intrinsic nerve abnormalities (such as bifid nerve, persistent median artery, poor gliding) or structures around the nerve leading to its entrapment The most frequently used US method in the identification of CTS is the evaluation of the crosssectional area of the median nerve (m-CSA) at various levels within the carpal tunnel mostly at inlet, mid-
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