Ultrasonography In Carpal Tunnel Syndrome Research Articles

The Inlet and Outlet Ratio: Retrospective and Prospective Study on an Improved Diagnostic Ultrasound Tool for Carpal Tunnel Syndrome

This study hypothesized that ratios of sonographic cross-sectional areas (CSAs) throughout the median nerve provide a more reliable tool for diagnosing carpal tunnel syndrome (CTS) than a single CSA value. We first tested this hypothesis in a retrospective cohort and subsequently confirmed it in a prospective blinded case-control series. Seventy patients were included in the retrospective study, and 50 patients and matched controls were included for the prospective study. We evaluated 4 CSAs, at the forearm, inlet, tunnel, outlet, and their ratios (Rforearm, Rinlet, Routlet, Routlet forearm) to evaluate compression of the median nerve. All patients underwent nerve conduction studies. For the prospective cohort, Disabilities of the Arm, Shoulder, and Hand scores and Boston Carpal Tunnel Questionnaire scores were evaluated, and ultrasound was performed by 2 examiners for each participant. The Boston and Disabilities of the Arm, Shoulder, and Hand scores showed worse subjective function in patients with CTS than in controls. Three ultrasonography parameters (CSAs at the inlet, Rinlet, and Routlet) correlated significantly with subjective function. Age and Rinlet were significantly correlated with severity of CTS in the nerve conduction studies. In both the retrospective and prospective patient groups, the numbers of CSAs at the inlet and outlet were significantly higher than that of CSAs at the tunnel, whereas in the control group, no such compression was found. Of the single measurements, CSAs at the inlet had the best diagnostic performance with an optimized cutoff of 11.75 mm2. The Rinlet and Routlet ratios performed even better and showed the highest adjusted odds ratios for predicting CTS of all parameters (cutoff Rinlet, 1.25; Routlet, 1.45). Inter-observer correlation was generally high, with better values for single CSAs than for ratios. The 3 CSA measurements of the median nerve and the associated ratios improved diagnostic power for ultrasonography in CTS in our study. Diagnostic I.

Correlation between Electrodiagnostic Study and Imaging Features in Patients with Suspected Carpal Tunnel Syndrome

Electrodiagnostic studies (EDXs) are the confirmative diagnostic tool for carpal tunnel syndrome (CTS). Previous studies have evaluated the relationship between EDXs and ultrasonography (US) but not with X-rays. Recently, many studies on the diagnostic value of X-rays in various diseases have been reported, but data on CTS are lacking. We evaluated the relationship between electrodiagnostic parameters and roentgenographic and ultrasonographic features in CTS and investigated the usefulness of X-rays and US for CTS. This retrospective study included 97 wrists of 62 patients. All patients with suspected CTS underwent EDXs, wrist US, and wrist X-rays. The CTS patients were classified into mild, moderate, and severe groups. The roentgenographic features included the ulnar variance (UV) and the anteroposterior diameter of the wrist (APDW), and the ultrasonographic features included the flattening ratio (FR) and the thickest anteroposterior diameter of the median nerve (TAPDM). Most EDX parameters showed significant correlations with roentgenographic and US features. The electrodiagnostic severity was also correlated with all imaging features. Therefore, both wrist X-rays and wrist US can be useful for the diagnosis of CTS as supplements to EDXs.

Ultrasonography for carpal tunnel syndrome in pregnancy: a prospective cross-sectional study

Confirmation of carpal tunnel syndrome (CTS) diagnosis with sonographic measurement of the median nerve cross sectional area (MN-CSA) is increasing in popularity. We aimed to analyse the ultrasonography (USG) values of MN-CSA in pregnant women with and without CTS symptoms. MN-CSAs of third trimester pregnant women were measured with USG and they were asked about the presence of CTS symptoms. Symptomatic participants were assigned to the CTS group and remaining participants were assigned to the Control group. The groups were compared according to MN-CSA. Twenty-five participants were grouped in CTS group and the remaining 64 participants were grouped in Control group. The MN-CSA was higher in the CTS group (9.44 ± 2.68) than in the Control group (7.20 ± 1.99), p = .00004. Obstetricians can use USG measurement of MN-CSA to confirm CTS diagnosis and consequently can offer conservative management, which is the widely accepted treatment modality in this cohort. Impact statement What is already known on this subject? CTS is the most common mononeuropathy of pregnancy, with up to 62% prevalence rates. The American Association of Neuromuscular & Electrodiagnostic Medicine practice guideline for the diagnosis of CTS recommends sonographic measurement of median nerve swelling at the carpal tunnel inlet as an accurate diagnostic test (Level A). What do the results of this study add? We found that a simple sonographic measurement of median nerve cross sectional area (MN-CSA) at the wrist appears to be a convenient method to confirm clinical CTS diagnosis in pregnant women. This study offers to use USG to confirm clinical CTS diagnosis in third trimester pregnant women before delivery. What are the implications of these findings for clinical practice and/or further research? This study will help to raise awareness of obstetricians about CTS during pregnancy. USG can be an effective first-line confirmatory test for CTS diagnosis in the pregnant population, but further research is necessary to determine a clear cut-off value for MN-CSA. We advise obstetricians to use sonographic measurement of MN-CSA in pregnant women with typical CTS symptoms, which will increase uniformity for consensus development. Obstetricians can offer advice for conservative management of CTS during pregnancy, which is the widely accepted treatment in this cohort.

Comparison of Diagnostic Accuracy of Electrodiagnostic Testing and Ultrasonography for Carpal Tunnel Syndrome.

Confirmatory methods such as electrodiagnostic testing (EDX) and ultrasonography (US) are currently used to support a clinical diagnosis of carpal tunnel syndrome (CTS). Scientific consensus long has preferred nerve conduction studies (NCS); however, recent studies have advocated for a diagnostic niche for ultrasound examination. This study seeks to compare diagnostic accuracies, sensitivity, and specificity between these 2 diagnostic tools. An institutional database was retrospectively analyzed to reveal 402 upper extremity cases (265 patients) with potential for CTS diagnosis. Demographics, NCS results, and US findings were determined for each patient case. Sensitivity and specificity values were determined for each diagnostic modality using Carpal Tunnel Syndrome 6 (CTS-6), a validated clinical CTS scoring system, as the reference standard. Demographic and diagnostic values were compared between positive and negative CTS groups using the 2-tailed t test and χ2 test. Electrodiagnostic testing resulted in a sensitivity of 87% and a specificity of 27%, whereas US produced a sensitivity of 76% and a specificity of 51%. No statistical difference was found in CTS-6 scores between NCS-positive and NCS-negative patient hands, whereas CTS-6 scores were significantly greater in US-positive CTS cases than US-negative cases (15.2 and 13.1, respectively, P < .001). Electrodiagnostic testing yields a greater sensitivity for CTS than US examination. However, US testing aligns more closely with CTS-6 scores and results in a greater specificity and positive predictive value. These findings suggest that US holds a non-trivial niche in CTS diagnosis and that EDX is not clearly preferable for all CTS diagnoses and cases.

Recent Advances in Ultrasound Diagnosis of Carpal Tunnel Syndrome.

With the widespread use of high-resolution ultrasonography, ultrasonic examination has been shown to be useful as a diagnostic method for carpal tunnel syndrome. The main advantages of ultrasonography are that it is simple, quick, non-invasive, and economical. Another advantage is that tissue dynamics can be observed with real-time imaging. In recent reports, it has been shown that ultrasonic examination can provide similar diagnostic accuracy as nerve conduction study in the diagnosis of carpal tunnel syndrome. It has been expected that ultrasound demand in daily medical care will continue to increase. Ultrasonography in carpal tunnel syndrome shows an enlarged median nerve in proximal carpal tunnel, thickening of the flexor retinaculum, and edema around flexor tendons in cross-sectional images. In addition, with the introduction of new technologies such as ultrasonic elastography and speckle tracking, it has become possible to quantify dynamics and material property changes of nerves, tendons, and their surrounding structures. In this review, we describe recent advancements of carpal tunnel syndrome diagnosis based on ultrasound dynamic images, and discuss its pathology.

High-resolution ultrasonography in carpal tunnel syndrome: role of ancillary criteria in diagnosis and response to steroid injection.

(1) Development and validation of a composite ultrasound score (cUSS) for the diagnosis of carpal tunnel syndrome (CTS). (2) To predict treatment response after local corticosteroid injection. Wrists of CTS patients and controls were evaluated with high-resolution ultrasound and cross-sectional area of median nerve at carpal tunnel inlet (CSAp) and outlet (CSAd) and bowing of flexor retinaculum (FRB), flexor tenosynovitis, and intraneural vascularity and echogenicity changes were noted. Patients were prospectively followed after ultrasound-guided corticosteroid injection. We studied 479 wrists of 141 patients and 99 controls. Optimal cut-offs for diagnosing CTS were 9.5mm2 and 10.5mm2, respectively, for CSAp and CSAd. A cUSS consisting of the following parameters was developed: age, CSAp, CSAd, FRB, and flexor tenosynovitis and echogenicity changes. External validation of cUSS yielded sensitivity, specificity, and diagnostic accuracy of 91.7%, 87.1%, and 89.8%, respectively. Treatment responses from 88 injections (median duration of follow-up of 6months) were available with satisfactory initial responses in 69.32% (61/88) and relapses in 30.86% (25/81). Median time to relapse was 2months. Initial response was predicted by FRB (odds ratio (OR): 5.43, 95% confidence interval (CI): 1.45-20.3, p = 0.012). Relapse was predicted by age (hazard ratio (HR) 1.168, 95% CI: 1.076-1.268, p = 0.0002), male gender (HR: 8.1.02, 95% CI: 2.394-27.422, p = 0.0007), FRB, (HR: 46.982, 95% CI: 5.048-437.293, p = 0.0008), and higher body mass index (HR: 0.238, 95% CI: 0.064-0.892, p = 0.0332). The developed cUSS has a diagnostic accuracy of 88% for diagnosing CTS. Ultrasound parameters could predict both initial treatment response and relapse. • Anatomical ultrasound parameters in addition to nerve cross-sectional area is important for diagnosis of CTS. • A composite US score for diagnosis of CTS was developed with accuracy 88.6%. • Bowing of flexor retinaculum predicts short and long term response to local steroid injection.

The correlation between pre-operative ultrasonographic median nerve evaluation and the operative procedure in CTS

BackgroundUltrasonography is a convenient non-invasive diagnostic tool with wide availability and cost effectiveness. Musculoskeletal ultrasonography is a growing field used for diagnosis of many musculoskeletal disorders; carpal tunnel syndrome (CTS) could be one of these disorders. The purpose of this study was to assess the impact of median nerve ultrasonography in carpal tunnel syndrome on surgical management, and its added value in operative techniques selection, and in tailoring the surgical steps. Thirty patients with CTS and thirty normal subjects underwent superficial ultrasonography. The cross-sectional area at different levels and flattening ratios were measured on both groups. The patients who had failed conservative treatment had surgical carpal tunnel release.ResultsThere was significant positive correlation between the need for external neurolysis with increased flattening ratio with cutoff values > 4, and between the need for approach extension with increased cross-sectional area difference between pisiform level and pronator quadratus level with cutoff values of cross-sectional area difference > 7.ConclusionsUltrasonographic measurements of median nerve in CTS could be helpful in selection and modification of operative procedure including the surgical approach and need for neurolysis.

S11-3. Ultrasonography for carpal tunnel syndrome

S11-3. Ultrasonography for carpal tunnel syndrome

The controversy of the normal values of ultrasonography in carpal tunnel syndrome: diagnostic accuracy of wrist-dependent CSA revisited.

No consensus exists about the upper limit of normal (ULN) of the cross-sectional area (CSA) of the median nerve in diagnosing carpal tunnel syndrome (CTS). Previously, we demonstrated a strong positive correlation between wrist circumference and CSA. ULN depending on wrist circumference turned out to have a low sensitivity, which was hypothesized to be caused by an age mismatch. The aim of this study was to re-evaluate the found invariance by augmentation of the healthy control group, adding older subjects, and to determine the diagnostic accuracy of the updated normal values. CSA and wrist circumference were measured in an additional 42 healthy controls in the ages of 40-60. Univariable and multivariable linear regression analyses were applied to determine predicting factors for CSA. Diagnostic accuracy was assessed in a prospective cohort of 253 patients. A strong correlation was found between wrist circumference and CSA (r = 0.61). Wrist circumference is the most important independent predictor for ULN (r2 = 0.37). We managed to simplify our newly derived regression equations, which turned out to be unrelated to age. Sensitivity of our new equations is low, but higher than a general fixed cut-off value (53.4% and 47.4%, respectively). Wrist circumference is the most important independent predicting factor of CSA. By using our updated equations and taking wrist circumference into account, one can determine a more precise ULN for each individual, which will lead to the improvement of the diagnostic accuracy of ultrasonography (US). Sensitivity for US in diagnosing CTS remains low and it can therefore not replace EDX.

Diagnostic Use of Ultrasonography in Carpal Tunnel Syndrome and Its Correlation with the Chinese Version of Boston Carpal Tunnel Questionnaire.

Introduction:There were yet no correlation studies performed between ultrasound and the Chinese version of Boston Carpal Tunnel Questionnaire (C-BCTQ). Besides, controversies still remain regarding the correlation between ultrasound and different language versions of BCTQ.Purpose of the Study:To examine whether ultrasound can (i) reflect symptom severity and/or functional status, (ii) differentiate primary/secondary symptom, and (iii) correlate with subscale items in C-BCTQ.Methods:Forty-two Chinese female individuals (aged 58.84 ± 9.02 years) with 73 hands were enrolled in the study. Factor analysis was used to identify the hidden factors of C-BCTQ. Correlations were examined between hidden factors, relevant subscale items of C-BCTQ, and ultrasound.Results:Three factors were identified as Factor One (functional status, 36.534%), Two (sensory symptoms, 15.057%) and Three (pain, 11.867%), with 63.458% of total variance explained in C-BCTQ. All the ultrasound parameters were positively correlated with Factor One (r = 0.29-0.411, P < 0.05), while no correlations were found with Factor Two and Three. Meanwhile, correlation between wrist cross-sectional area and functional status scale (FSS) was also found (W-CSA, r = 0.266, P = 0.023), whereas no correlation was found with symptom severity scale (SSS), subscales of primary symptom (Paresthesia) and secondary symptom (pain) related items in C-BCTQ.Conclusion:Morphological information via ultrasound can reflect the impact on functionality that carpal tunnel syndrome (CTS) exerted. However, it can be used neither to describe symptom severity nor differentiate primary/secondary symptom of CTS.

Quantitative Muscle Ultrasonography in Carpal Tunnel Syndrome.

ObjectiveTo assess the reliability of quantitative muscle ultrasonography (US) in healthy subjects and to evaluate the correlation between quantitative muscle US findings and electrodiagnostic study results in patients with carpal tunnel syndrome (CTS). The clinical significance of quantitative muscle US in CTS was also assessed.MethodsTwenty patients with CTS and 20 age-matched healthy volunteers were recruited. All control and CTS subjects underwent a bilateral median and ulnar nerve conduction study (NCS) and quantitative muscle US. Transverse US images of the abductor pollicis brevis (APB) and abductor digiti minimi (ADM) were obtained to measure muscle cross-sectional area (CSA), thickness, and echo intensity (EI). EI was determined using computer-assisted, grayscale analysis. Inter-rater and intra-rater reliability for quantitative muscle US in control subjects, and differences in muscle thickness, CSA, and EI between the CTS patient and control groups were analyzed. Relationships between quantitative US parameters and electrodiagnostic study results were evaluated.ResultsQuantitative muscle US had high inter-rater and intra-rater reliability in the control group. Muscle thickness and CSA were significantly decreased, and EI was significantly increased in the APB of the CTS group (all p<0.05). EI demonstrated a significant positive correlation with latency of the median motor and sensory NCS in CTS patients (p<0.05).ConclusionThese findings suggest that quantitative muscle US parameters may be useful for detecting muscle changes in CTS. Further study involving patients with other neuromuscular diseases is needed to evaluate peripheral muscle change using quantitative muscle US.

Ultrasound assessment of the median nerve: a biomarker that can help in setting a treat to target approach tailored for carpal tunnel syndrome patients.

Ultrasonography (US) is a valuable tool for confirming the diagnosis of carpal tunnel syndrome (CTS) as it enables the detection of changes in the median nerve shape and rule out anatomic variants as well as space-occupying lesions such as ganglion cysts or tenosynovitis. This work was carried out aiming at: 1. Ultrasonography assessment of the median nerve and its neurovascular blood-flow in CTS patients before and after management. 2. Verify the possibility of using baseline US parameters as a biomarker to predict likely outcomes and frame a treatment plan for CTS patients.233 CTS subjects diagnosed based on clinical and electrophysiological (NCS) testing were included in this work. US measures at the tunnel inlet included: cross sectional area, flattening ratio and neural Power Doppler (PD) signals. Patients who had severe NCS outcomes or neurological deficit were referred for open surgical decompression; the remaining patients were given the choice of either conservative or surgical management. The main outcome variable was improvement >70% in CTS symptoms. Assessments were carried out at baseline, 1-week, 1-month and 6-months post treatment. Results revealed an inverse relation between the neural vasculature and CTS severity defined by NCS (r = − 0.648). In CTS cases treated conservatively, the US measures started to improve within 1-week, whereas in the surgically treated cohort there was an initial phase of post-operative nerve measures increase, before settling at 1-month time of follow-up. The risk of poor outcomes was significantly higher (RR 3.3) in patients with high median nerve flattening ratio. This risk was most marked in the cohort with nerve flattening associated with longer duration of illness (RR 4.3) and low PD signal (RR 4.1). The results revealed that in addition to the diagnostic value of US in CTS, the detection of increased median nerve neuro-vasculature has a good prognostic value as an indicator of early median nerve affection.

Ultrasound: A Screening Tool for Carpal Tunnel Syndrome

Abstract Background Electrodiagnostic test is considered as the gold standard for diagnosis of carpal tunnel syndrome (CTS). Ultrasonography provides a simple non-invasive means of visualising peripheral nerve pathology. Objective The objective of the study was to assess the role of ultrasonography in CTS and its correlation with the present day gold standard of nerve conduction studies (NCS). Materials and Methods A prospective cohort size of 100 subjects was calculated based on a hypothesized sensitivity of 90% and a confidence interval of 85-95%. All 100 subjects, 64 controls and 36 patients underwent nerve conduction studies and USG. Transverse images of the median nerve were obtained at three levels: proximal to the carpal tunnel inlet, at the carpal tunnel inlet and at the carpal tunnel outlet. The flattening ratio was also assessed at the tunnel inlet and outlet. Statistical analysis was done to corelate the ultrasound findings at each level with nerve conduction studies and calculation of the positive and negative predictive values. The cut offs of the cross-sectional areas of the median nerve at the three anatomical levels on ultrasonography were taken at the best sensitivity and specificity according to the ROC curve. Results We found that at any one anatomical level, the sensitivity of ultrasound to detect carpal tunnel syndrome by increase in the cross-sectional area of median nerve as compared to the nerve conduction studies is 90%. Conclusions At 45% specificity, ultrasonography could be used as a non-invasive and easily available screening tool in carpal tunnel syndrome. Also, the best level to look for nerve compression is at the level of the carpal tunnel inlet.

Value of Ultrasonography in the Diagnosis of Carpal Tunnel Syndrome: Correlation with Electrophysiological Abnormalities and Clinical Severity

ObjectiveTo investigate a diagnostic value of ultrasonography in carpal tunnel syndrome (CTS) patients and to evaluate a correlation of sonographic measurements with the degree of electrodiagnostic abnormalities and clinical severity.MethodsTwo-hundred-forty-six symptomatic hands in 135 patients and 30 asymptomatic hands in 19 healthy individuals as control group were included. In ultrasonographic study, we measured the cross-sectional area (CSA) and flattening ratio (FR) of the median nerve at the pisiform as well as palmar bowing (PB) of the flexor retinaculum. Sensitivity and specificity of ultrasonographic measurements were evaluated and ultrasonographic data from the symptomatic and control hands were compared to the grade of electrodiagnostic and clinical severity.ResultsThe mean CSA was 13.7±4.2 mm2 in symptomatic hands and 7.9±1.3 mm2 in asymptomatic hands. The mean FR was 4.2±1.0 in symptomatic hands and 3.4±0.4 in asymptomatic hands. The mean PB was 3.5±0.5 mm in symptomatic hands and 2.6±0.3 mm in asymptomatic hands. Statistical analysis showed differences of the mean CSA, FR and PB between groups were significant. A cut-off value of 10 mm2 for the mean CSA was found to be the upper limit for normal value. Both the mean CSA and PB are correlated with the grade of electrophysiological abnormalities and clinical severity, respectively.ConclusionUltrasographic measurement of the CSA and PB is helpful to diagnose CTS as a non-invasive and an alternative modality for the evaluation of CTS. In addition, ultrasonography also provides a reliable correlation with the grade of electrodiagnostic abnormalities and clinical severity.

Quantitative Muscle Ultrasonography in Carpal Tunnel Syndrome

Quantitative Muscle Ultrasonography in Carpal Tunnel Syndrome

The diagnostic value of ultrasonography in carpal tunnel syndrome: a comparison between diabetic and non-diabetic patients

BackgroundTo compare the value of ultrasonography for diagnosing carpal tunnel syndrome (CTS) in patients with and without diabetes mellitus (DM).MethodsEighty non-DM and 40 DM patients with electromyography-confirmed CTS were assessed and underwent high-resolution ultrasonography of the wrists. Cross-sectional area (CSA) and flattening ratio (FR) of the median nerve were measured at the carpal tunnel outlet (D) and wrist crease (W).ResultsThe 80 non-DM and 40 DM patients had 81 and 59 CTS-hands, respectively. The CSA_D and CSA_W were significantly larger in the CTS-hands and DM-CTS-hands compared to the normal control (p < 0.001). However, there is no difference of CSA_D and CSA_W between DM and non-DM CTS patients. Receiver operating characteristics [ROC] curve analysis revealed that CSA_W ≥13 mm2 was the most powerful predictor of CTS in DM (area under curve [AUC] = 0.72; sensitivity 72.9%, specificity 61.9%) and non-DM (AUC = 0.72; sensitivity 78.5%, specificity 53.2%) patients. The CSA positively correlated with the distal motor latency of the median compound motor action potential (CMAP), distal sensory latency of the median sensory nerve action potential (SNAP), and latency of the median F wave, but negatively correlated with the amplitude of the median CMAP, amplitude of the median SNAP, and sensory NCV of the median nerve. Stepwise logistic regression revealed that CSA_W (OR 1.21, 95% CI 1.07-1.38; p = 0.003) was independently associated with CTS in DM patients and any 1 mm2 increase in CSA_W increased the rate of CTS by 28%.ConclusionsThe CSA of the median nerve at the outlet and wrist crease are significantly larger in CTS hands in both DM and non-DM patients compared to normal hands. The CSA of the median nerve by ultrasonography may be a diagnostic tool for evaluating CTS in DM and non-DM patients.

Provocation tests in doppler ultrasonography for carpal tunnel syndrome

Doppler ultrasonography (DU) has recently been shown to be useful in imaging carpal tunnel syndrome (CTS). In this study, we aim to characterize the changes seen after exercise and electrical stimulation. Five patients with CTS were recruited with 5 age-matched subjects. DU was used to visualize the median nerve, flexor tendon, and bone at base line and after 1 minute of: (a) median nerve motor stimulation, (b) median nerve sensory stimulation, (c) abductor pollicis brevis contraction, and (d) adductor digiti minimi contraction. Blood flow in the median nerve was greater after APB exercise. Furthermore, blood flow in the median nerve was greater in cases than controls after APB exercise. At baseline, blood flow in the flexor tendon was greater in cases than controls. While limited by sample size, this study demonstrates that exercise of median innervated muscles may be useful in enhancing diagnostic utility of DU for CTS.

P30-17 Median nerve ultrasonography in carpal tunnel syndrome: a blinded prospective case-control study

P30-17 Median nerve ultrasonography in carpal tunnel syndrome: a blinded prospective case-control study

Diagnostic usefulness of ultrasonography in carpal tunnel syndrome: Review of the literature

The diagnosis of carpal tunnel syndrome (CTS) is based on a combination of characteristic symptoms and electrophysiologic abnormalities. Although nerve conduction study is considered as the gold standard for CTS diagnosis, the attraction of sonography for diagnosis of CTS lies in its wide availability, lower cost, noninvasiveness, and shorter examination time. We present a review of the literatures concerning sonography for. the diagnosis of CTS. The main conclusion is that there is no competition but rather a complementarity between sonography and electrodiagnosis. Sonography is certainly an efficient imaging technique but can not replace electrophysiologic study.

Median nerve ultrasonography in carpal tunnel syndrome: Findings from two laboratories

Ultrasonographic (US) enlargement of the median nerve at the wrist is known to be consistent with carpal tunnel syndrome (CTS), although the effects of different measurement techniques, equipment, and patient populations remain unknown. The purpose of this study was to examine the similarities and differences of US findings in CTS between two electromyography (EMG) laboratories. In 2006 and 2007, US measurements of the median nerve were recorded independently and statistically analyzed in patients with CTS at two EMG laboratories (Duke University, Durham, NC, USA, and Università Cattolica del Sacro Cuore, Rome, Italy). Patient age, median nerve area in the forearm, and neurophysiologic score did not differ significantly between the two laboratories. The North Carolina group had a larger median nerve area at the wrist and wrist-to-forearm ratio than the Italian group, although both were elevated in reference to established values for the diagnosis of CTS. Median nerve US is less susceptible to differences between laboratories than previously thought, permitting greater generalization of findings.