Ultrasound Parameters Other Than the Direct Measurement of Ulnar Nerve Size for Diagnosing Cubital Tunnel Syndrome: A Systemic Review and Meta-analysis.

Abstract

To investigate the diagnostic performance of available ultrasound (US) parameters, other than the direct measurements of ulnar nerve size, that is, cross-sectional area (CSA) and diameter, for diagnosing cubital tunnel syndrome (CuTS). Databases, including PubMed and Embase, were searched from the earliest record of CuTS US to April 24, 2018. Published studies (N=13) comparing US parameters of ulnar nerves between patients with CuTS and patients without CuTS were included. Study design, participants' demographics, diagnostic references of CuTS, and US parameters other than the direct measurements of the ulnar nerve size were retrieved from the included studies. This systematic review comprised 663 CuTS patients and 543 patients without CuTS. The pooled nerve swelling ratio in the CuTS group was significantly larger than that of the controls. The mean between-group differences of CSA_{Max or ME}/CSA_arm, CSA_{Max or ME}/CSA_forearm and CSA_{Max or ME}/CSA_wrist were 1.03 (95% confidence interval [CI], 0.77-1.29), 1.38 (95% CI, 0.93-1.82), and 0.83 (95% CI, 0.56-1.11), respectively. Regarding the swelling ratio of CSA_{Max or ME} /CSA_arm, the pooled sensitivity and specificity available from the 3 included studies were 0.67 (95% CI, 0.59-0.74) and 0.81 (95% CI, 0.75-0.86), respectively. Similarly, for the swelling ratio of CSA_{Max or ME}/CSA_forearm, the pooled sensitivity and specificity were 0.62 (95% CI, 0.54-0.69) and 0.86 (95% CI, 0.81-0.90), respectively. Other US parameters identified in this review included nerve-flattening ratio (maximum diameter/minimum diameter), nerve-to-tunnel ratio (ulnar nerve CSA/cubital tunnel CSA), nerve echogenicity, and intraneural vascularity, all of which were reported in a minority of included articles. Despite the insufficient number of pertinent studies to prove its superiority to other US measurements, the ulnar nerve-swelling ratio can be a complementary tool for diagnosing CuTS. The presence of intraneural vascularity, increased flattening ratio, and enlarged intraneural hypoechoic fraction also seem to be potential US indicators for CuTS diagnosis, which need to be validated with more prospective studies.