RESUMO
We analyze the effectiveness of ultrasonography in diagnosing carpal tunnel syndrome (CTS) and propose the use of sonographic index of median nerve (MN) in carpal tunnel (SIMNCT) in a diagnostic algorithm and in establishing a scale of severity.We studied a group of 344 patients with CTS symptoms, examining them by ultrasound. We measured in all patients, on the affected hand: the size of the cross-sectional area of the MN at carpal tunnel (CT) inlet and outlet, nerve morphology at passage through CT, the vertical thickness of the MN entering into the CT - G1, the lowest vertical thickness into the CT or leaving the CT - G2, the thickness of the MN in the transversal plane as entering in the CT - L. Normal values were considered the similar measurements taken on the healthy hand and we established as normal SIMNCTâ=â16%. We proposed the formula SIMNCTâ=â100% (1-G2/G1) in order to calculate the index.Statistics show a significant sensitivity of SIMNCT (Pâ<â.0001) compared with cross-sectional area (CSA) and flattening ratio in the diagnosis of CTS. Analyzing the SIMNCT developed by us, we demonstrated a sensitivity of 94.81% and a specificity of 99.66% in CTS diagnosis. Thereby, we propose a CTS severity classification: normalâ=â16%, mildâ=â16-19%, moderateâ=â19% to 28%, severeâ=â28% to 50%, very severeâ>â50%.Ultrasonography is an effective method of studying the morphology of the tunnel and compressed nerve at various CTS stages and determining the cause of compression. The SIMNCT is a valuable and practical indicator and it can be used in the CTS diagnosis.