Baseline Characteristics of the Median Nerve on Ultrasound Examination

Abstract

Background: Previous studies using ultrasound for diagnosis of carpal tunnel syndrome have reported on relatively small series of patients, leading to large standard deviations and/or confidence intervals for the mean cross-sectional area of the median nerve. The purpose of this study is to define the CSA of the median nerve in a large cohort of patients. Methods: Patients (n = 175) without history of carpal tunnel release were recruited. All participants were evaluated using the Carpal Tunnel Syndrome-6 questionnaire, a validated clinical diagnostic tool, with a score of 12 or greater considered positive for CTS. Ultrasound examination was performed on both wrists of all participants using a 13-6 MHz linear array transducer. Results: The mean median nerve CSA was significantly larger (P < .001) for patients with a positive (mean = 11.16, SD = 2.51) versus negative CTS-6 result (mean = 6.91, SD = 2.06). There was a significant correlation (.527, P < .001, n = 349) between CSA and CTS-6 score. Logistic regression analysis determined that a CSA of 10 mm2 optimized sensitivity and specificity at 80% and 88%, respectively. Accuracy was 87.9%. Conclusions: A significant difference in mean CSA was found between patients with and without CTS. Median nerve CSA showed a statistically significant positive correlation with CTS-6. Similar to prior studies, a CSA of 10 mm2 was determined to be the optimal cutoff. In this large series of patients, ultrasound was a sensitive, specific, and accurate test for confirmation of a clinical diagnosis of CTS.

Ultrasonography for the diagnosis of carpal tunnel syndrome: correlation of clinical symptoms, cross-sectional areas and electroneuromyography

“…There is some overlap in distributions between normal or pathological cross-sectional area values. Normal measurements from the inlet area are between 8 and 14 mm 2 (Pan et al, 2016); this variation is possibly due to issues of resolution, machine settings, patient size and individual examination technique. In most studies, the set cut-off value of cross-sectional area is 9 to 11 mm 2 (Tai et al, 2012).…”

“…In addition, high-quality US devices have become significantly cheaper, which makes it possible to acquire and use these devices in routine hand surgery practice. Despite this, there are ongoing debates about the best location to measure the median nerve and the thresholds for confirming the diagnosis of CTS (Ng et al, 2018;Pan et al, 2016;Torres-Costoso et al, 2018). Such information may be helpful in establishing the use of ultrasonography in a routine outpatient clinic visit.…”

Sensitivity of high-resolution ultrasonography in clinically diagnosed carpal tunnel syndrome patients with hand pain and normal nerve conduction studies

“… 3 , 4 , 7 , 8 Ultrasonography is an alternative confirmatory method for the diagnosis of CTS, according to recently published meta-analyses, 17 restricting the role of electrodiagnosis to people with advanced axonal loss and suspected for differential diagnosis. 18 We chose to measure CSA of the median nerve at the carpal tunnel inlet, as this has been found to be the most sensitive and specific sonographic variable, based on a literature review of published abstracts between 2000 and 2017, 3 , 18 , 19 as well as a recent meta-analysis published by the AANEM. 20 However, no exact normal ranges for median nerve CSA and cutoff point for detecting CTS have been developed, mainly due to variations in equipments, measurement techniques, patients’ characteristics and so the variable location of maximum CSA or median nerve swelling, etc.…”

Ultrasound of the Median Nerve in the Surgical Treatment of Severe Carpal Tunnel Syndrome

“…2-4 Enlargement of the median nerve at the carpal tunnel inlet on ultrasound with a cross-sectional area (CSA) of ≥10 mm 2 is considered positive for CTS, with EDX-confirmed severe cases exceeding 12 mm 2 . 2,5,6 Furthermore, a ratio of CSA measurements at the wrist compared with the forearm allows patients to serve as their own control, and a wrist/forearm ratio (WFR) greater than 1.4 is supportive of CTS. 7,8…”