The diagnostic accuracy of median nerve ultrasonography in elderly patients with carpal tunnel syndrome: sensitivity and specificity assessment

BACKGROUND: Accurate diagnosis of carpal tunnel syndrome (CTS), the most common entrapment neuropathy, and its differentiation from other diseases are essential, especially in older individuals with advanced symptoms and modified electrophysiological abnormalities. The current study was conducted to evaluate the diagnostic accuracy of ultrasonography (US), regarding sensitivity and specificity in the diagnosis of CTS in elderly patients. METHODS: Individuals with upper limb complaints and reference subjects were recruited from the Rofaydeh Hospital, Tehran, Iran, from June 2013 to October 2014 – (15 months). We evaluate case and control subjects for health status, demographics, clinical characteristics of CTS, median nerve physiology by electrodiagnostic tests, and anatomy by US. Median nerve cross-sectional area (CSA) at precanal, tunnel inlet, midcanal, tunnel outlet, and antecubital levels was measured applying US examination. RESULTS: Of the 723 complaining patients, we assessed 380 patients with CTS symptoms. Electrodiagnostic studies (EDX) confirmed the CTS diagnosis in 203 of these clinically diseased patients. A total of 103 patients (of the 113 reference subjects) had normal EDX in the reference group. Comparisons of wrists between the afflicted and reference subjects demonstrated the CSA at precanal, tunnel inlet, midcanal, and tunnel outlet levels being significantly more abundant in the diseased hands than in the nondiseased hands. CSA at the tunnel inlet and the inlet-to-antecubital CSA ratio with a threshold of 8.5 mm(2) and 0.65 gave the best diagnostic accuracy with a sensitivity and specificity of 96.9 and 93.6% for the inlet CSA and 99 and 28% for the CSA ratio, respectively. CONCLUSION: The US as a noninvasive diagnostic method may serve for the investigation of CTS in elderly patients with excellent sensitivity and specificity.