Carpal Tunnel Inlet Research Articles

Role of Ultrasonography and Color Doppler versus Nerve Conduction Test Results in Evaluation of Cases of Carpal Tunnel Syndrome

Abstract Background Carpal tunnel syndrome (CTS) is a common entrapment neuropathy with incidence rate of 2.7 to 5.8% of the general population. Nerve conduction studies (NCS) were considered gold standard for diagnosis. Due to false negative rate, Ultrasonography (US) evaluation of median nerve (MN) was suggested as a diagnostic test for CTS. Aim of the Work Our aim was to investigate the diagnostic accuracy of US derived measurements compared to NCS for the diagnosis of CTS and comparing different US derived measurements and ratios to know which could be used efficiently for the diagnosis of CTS. Patients and Methods This case control study included 52 participants; 26 cases and 26 healthy controls. Our results showed comparable sensitivity between US and NCS results which was 88% and 96.2, respectively. On the other hand, specificity with US measurements was 92% compared to 88% in case of NCS. Results Many US derived measurements as inlet MN CSA, outlet CSA, largest CSA between inlet and outlet, WFR and IOR showed statistically highly significant correlation with clinical diagnosis of CTS. Other measurements like CSA at proximal border and proximal third of pronator quadratus muscle failed to show statistically significant correlation. Conclusion US results are comparable to NCS results in cases of CTS. US derived measurements as MN CSA at carpal tunnel inlet and largest CSA between inlet and outlet were best to be used for correlation with clinical diagnosis with cut-off value = 9.35 and 9.3 cm2, respectively. WFR and IOR have also high correlation with clinical diagnosis with cut-off value = 1.1 and 1.02, respectively.

Ultrasound vs Nerve Conduction Studies: A Comparative Analysis in Carpal Tunnel Syndrome Diagnosis

Background: Carpal tunnel syndrome (CTS) is a prevalent entrapment neuropathy. While nerve conduction studies (NCS) remain the gold standard for diagnosis, ultrasound (USG) offers a non-invasive alternative. This study aimed to compare the diagnostic accuracy of USG and NCS in CTS at Dr. Mohammad Hoesin General Hospital Palembang, Indonesia. Methods: A cross-sectional study was conducted on patients presenting with CTS symptoms. Demographic and clinical data were collected. NCS and USG assessments were performed, blinded to each other's results. USG measurements included the cross-sectional area at the carpal tunnel inlet (CSAc), proximal to the carpal tunnel (CSAp), and the difference between them (∆CSA). Diagnostic accuracy was calculated, and agreement was assessed using Cohen's kappa. Results: A total of 86 wrists from 49 patients were included. The mean age was 52 ± 11 years, with a female predominance (86%). The majority had mild CTS based on NCS (55.8%). USG measurements showed mean CSAc of 13.1 ± 3.5 mm², CSAp of 10.6 ± 3.0 mm², and ∆CSA of 2.5 ± 0.9 mm². ∆CSA had the highest sensitivity (92.2%), specificity (88.9%), and accuracy (91.9%), with substantial agreement with NCS (Kappa = 0.65). Conclusion: USG, particularly using ∆CSA, demonstrates high diagnostic accuracy in CTS, comparable to NCS. It can serve as a valuable tool, especially in settings with limited NCS availability.

Automated segmentation of the median nerve in patients with carpal tunnel syndrome

Machine learning and deep learning are novel methods which are revolutionizing medical imaging. In our study we trained an algorithm with a U-Net shaped network to recognize ultrasound images of the median nerve in the complete distal half of the forearm and to measure the cross-sectional area at the inlet of the carpal tunnel. Images of 25 patient hands with carpal tunnel syndrome (CTS) and 26 healthy controls were recorded on a video loop covering 15 cm of the distal forearm and 2355 images were manually segmented. We found an average Dice score of 0.76 between manual and automated segmentation of the median nerve in its complete course, while the measurement of the cross-sectional area at the carpal tunnel inlet resulted in a 10.9% difference between manually and automated measurements. We regard this technology as a suitable device for verifying the diagnosis of CTS.

Median Nerve Cross-Sectional Area and Carpal Tunnel Syndrome in Specific Populations: Sonographic Analysis of Patients With Type 2 Diabetes or Bifid Anatomy.

Evaluate diagnostic accuracy of median nerve cross-sectional area (CSA) to determine severity versus presence of carpal tunnel syndrome (CTS) across existing electrodiagnostic-based (EDX) classification systems in patients with type 2 diabetes or bifid anatomy. Retrospective analysis of cross-sectional patient data. Receiver operating characteristic analysis used to determine median nerve CSA cutoff values and associated diagnostic likelihood ratios for all consolidated and binary EDX-based classifications of CTS in patients with type 2 diabetes or bifid anatomy. Determine shifts in diagnostic probability based on established cutoff values and associated likelihood ratios. Distal CSA measured at or near carpal tunnel inlet, proximal CSA at level of pronator quadratus muscle, and delta CSA by subtracting proximal from distal. Binary categorizations of CTS were statistically superior to consolidated categorizations of CTS severity in patients with type 2 diabetes or bifid anatomy. Binary categorizations established reasonably consistent median nerve CSA cutoff values across all EDX-based classifications examined resulting in the following for distal CSA or delta CSA: ≤10 or ≤4 mm2 to rule out and ≥11 or ≥5 mm2 to rule in CTS, respectively. These cutoff values resulted in small shifts in diagnostic probability in patients with type 2 diabetes and small to conclusive shifts in diagnostic probability in patients with bifid anatomy. Binary categorizations to rule out or rule in CTS based on the proposed cutoff values provide the most meaningful information about shifts in diagnostic probability across all EDX-based classifications examined. The use of median nerve CSA to categorize severity of CTS is not recommended in patients with type 2 diabetes or bifid anatomy.

Reliability of Ultrasound Measurements of the Median Nerve in Asymptomatic Subjects Using a Handheld Device.

This study investigated the reliability of measuring the median nerve cross-sectional area (CSA) at the carpal tunnel inlet using a handheld ultrasound device (HUD) compared to a standard ultrasound system, focusing on intra- and inter-operator reproducibility among novice and expert operators. Employing a prospective cross-sectional design, 37 asymptomatic adults were assessed using both devices, with measurements taken by an expert with over five years of experience and a novice with less than six months. The CSA was determined using manual tracing and ellipse methods, with reproducibility evaluated through intraclass correlation coefficients (ICCs) and agreement assessed via Bland-Altman plots. Results showed a high degree of agreement between the devices, with excellent intra-operator reproducibility (ICC > 0.80) for the expert, and moderate reproducibility for the novice (ICCs ranging from 0.539 to 0.841). Inter-operator reliability was generally moderate, indicating acceptable consistency across different experience levels. The study concludes that HUDs are comparable to standard ultrasound systems for assessing median nerve CSA in asymptomatic subjects, with both devices providing reliable measurements. This supports the use of HUDs in diverse clinical environments, particularly where access to traditional ultrasound is limited. Further research with a larger sample and symptomatic patients is recommended to validate these findings.

Diagnostic efficacy of high-frequency Grey-scale ultrasonography and Sono-elastography in grading the severity of carpal tunnel syndrome in comparison to nerve conduction studies.

To correlate the cross-sectional area (CSA) and elasticity of the median nerve (MN) measured at carpal tunnel inlet between healthy controls and various degrees of carpal tunnel syndrome (CTS) graded as per nerve conduction studies (NCS). A total of 53 patients (with 81 wrists) presenting with clinical symptoms characteristic of CTS, having their diagnosis confirmed and severity graded by NCS, and 48 healthy controls (with 96 wrists) were included in the study. All the study participants underwent wrist ultrasound which included initial Grey-scale USG followed by strain and shear wave elastography. The CSA and elasticity (in terms of strain ratio and shear modulus) of MN were measured at the carpal tunnel inlet. Statistical analysis was performed using the Mann-Whitney U test to compare between the two groups and for subgroup analysis of cases. The diagnostic performance of each variable was evaluated using the receiver operating characteristic curves. The mean CSA was 9.20 ± 1.64, 11.48 ± 1.05, 14.83 ± 1.19 and 19.87 ± 2.68 mm2, the mean shear modulus was 17.93 ± 2.81, 23.59 ± 2.63, 32.99 ± 4.14 and 54.26 ± 9.24kPa and the mean strain ratio was 5.26 ± 0.68, 5.56 ± 0.70, 7.03 ± 0.47 and 8.81 ± 0.94 in control, mild, moderate and severe grades of CTS, respectively (p < 0.001). The combined utility of Grey-scale USG and Elastography may serve as a painless and cost-effective alternative to NCS in grading the severity of CTS.

Median Nerve Shear Wave Elastography Is Associated With the Neurophysiological Severity of Carpal Tunnel Syndrome.

This study examines the associations between the median nerve (MN) shear wave elastography (SWE), the MN cross-sectional area (CSA), patient's symptoms, and the neurophysiological severity of carpal tunnel syndrome (CTS). The most appropriate site to perform SWE was also tested. This prospective study comprised 86 wrists of 47 consecutive patients who volunteered for MN ultrasound after an electrodiagnostic study. The neurophysiological severity of CTS was assessed according to the results of a nerve conduction study (NCS). The MN CSA was measured at the carpal tunnel inlet (wCSA) and the forearm (fCSA). SWE was performed on the MN in a longitudinal orientation at the wrist crease (wSWE), at the forearm (fSWE), and within the carpal tunnel (tSWE). The wCSA and wSWE correlated positively with the neurophysiological severity of CTS (r = .619, P < .001; r = .582, P < .001, respectively). The optimal cut-off values to discriminate the groups with normal NCS and with findings indicating CTS were 10.5 mm2 for the wCSA and 4.12 m/s for the wSWE. With these cut-off values, wCSA had a sensitivity of 80% and specificity of 87% and wSWE a sensitivity of 88% and specificity of 76%. Neither tSWE nor fSWE correlated with the neurophysiological severity of CTS or differed between NCS negative and positive groups (P = .429, P = .736, respectively). Shear wave velocity in the MN at the carpal tunnel inlet increases in CTS and correlates to the neurophysiological CTS severity equivalently to CSA measured at the same site.

Time-Dependent Change in Carpal Tunnel Cross-Sectional Area and Transverse Carpal Ligament Thickness Using Serial Magnetic Resonance Imaging Studies—An Anatomical Study

Idiopathic carpal tunnel syndrome (CTS) is a common compressive neuropathy. Aging and female sex are risk factors, but the reasons are unclear. The purpose of this study was to evaluate whether identifiable radiographic changes resulting in a decrease in carpal tunnel area (CTA) over time exist. A database search of a multicenter, academic, tertiary institution from 1998 to 2021 identified 433 patients with serial wrist magnetic resonance images (MRI) at least 5 years apart. Fifty-six met the inclusion criteria with adequate films to measure CTA and transverse carpal ligament (TCL) thickness at the same slice location-the carpal tunnel inlet, hook of the hamate, and carpal tunnel outlet-independently by two observers who were blinded to each other's measurements. Rates for the change in CTA and TCL thickness were calculated at all three locations. Thickness of the TCL increased, whereas that of the CTA decreased over time. Inlet CTA decreased by 0.9 mm2 per year (95% CI: 0.34-1.5), outlet CTA decreased by 1.8 mm2 per year (95% CI: 1.2-2.5), and CTA at the hook of the hamate decreased by 1.6 mm2 per year (95% CI: 1.0-2.0 per year). The TCL thickened by 0.02 mm per year at all three sections. Taller patients had a decreased rate of CTA loss. In this select cohort, TCL thickened and CTA decreased with time. TCL thickening accounted for about half of the variation in CTA, suggesting that this is a possible contributor to this change. Hypertrophy of the carpal tunnel floor may account for the remaining variation in CTA. The question of whether these results are reliable and generalizable to the general population, or a major influence in the pathophysiology of CTS, is unknown. Small decreases in CTA and thickening of the TCL occur with aging. Whether this is a contributing factor in the development of CTS requires further study.

Sonographic evaluation of median nerve cross-sectional area in a normal Iranian population: A cross-sectional study.

Considering disagreements on the normal range of median nerve cross-sectional area (MNCSA) and insufficient data in the Iranian population, this study aimed to measure normal MNCSA. In this cross-sectional study, bilateral upper limbs of 99 subjects were assessed by sonography, and MNCSA was measured at three levels: forearm, carpal tunnel inlet (CTI), and carpal tunnel outlet (CTO). The association between MNCSA and demographic factors was assessed. Mean MNCSA was 6.33 mm2 at the forearm, 9.41 mm2 at CTI, and 10.67 mm2 at CTO. MNCSA was significantly higher in males (6.78 vs. 5.94 mm2 at the forearm, 9.98 vs. 8.92 mm2 at CTI, and 11.24 vs. 10.84 mm2 at CTO in males and females, respectively) and taller (>170 cm) subjects in all three levels (6.69 vs. 6.03 mm2 at the forearm, 9.80 vs. 9.02 mm2 at CTI, and 11.27 vs. 10.12 mm2 at CTO in taller and shorter subjects, respectively). MNCSA was not significantly associated with wrist ratio (WR) or body mass index (BMI). The normal MNCSA range in the Iranian population is 6.31 mm2 (forearm) to 10.74 mm2 (CTO). MNCSA is significantly higher in males and taller subjects but is not associated with BMI and WR.

Sonographic reference values for median nerve cross-sectional area: A meta-analysis of data from healthy individuals.

Establish median nerve CSA reference values and identify patient-level factors impacting diagnostic thresholds. Studies were identified through a robust search of multiple databases, and quality assessment was conducted using a modified version of the National Institute of Health Study Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. A meta-analysis was performed to identify normative values stratified by anatomic location. A meta-regression was conducted to examine heterogeneity effects of age, sex, and laterality. The meta-analysis included 73 studies; 41 (56.2%) were high quality. The median nerve CSA [95% CI] was 6.46mm2 [6.09-6.84], 8.68mm2 [8.22-9.13], and 8.60mm2 [8.23-8.97] at the proximal forearm, the carpal tunnel inlet, and the proximal carpal tunnel, respectively. Age was positively associated with CSA at the level of proximal carpal tunnel (β=0.03mm2, p=0.047). Men (9.42mm2, [8.06-10.78]) had statistically larger proximal tunnel CSA (p = 0.03) as compared to women (7.71mm2, [7.01-8.42]). No difference was noted in laterality. A reference value for median nerve CSA in the carpal tunnel is 8.60mm2. Adjustments may be required in pediatrics or older adults. The diagnostic threshold of 10.0mm2 for male patients should be cautiously applied as the upper limit of normative averages surpasses this threshold.

EVALUATION OF THE EFFECT OF HAND DOMINANCE ON MEDIAN NERVE CROSS-SECTIONAL AREA AMONG HEALTHY ADULT SUBJECTS: A CROSS-SECTIONAL STUDY

Background:This study was designed considering the existing controversies on the normal range of median nerve cross-sectional area (MNCSA) and its association with hand dominance. Methods:In this cross-sectional descriptive study, the upper limbs of 100 healthy subjects (46 men and 54 women) were assessed bilaterally by sonography. MNCSA was measured at the level of the carpal tunnel inlet. Results:Calculated MNCSA values were 9.29 mm2 and 9.54 mm2 for the right and left sides, respectively. No significant difference was observed between the right and left hands. No significant correlation was observed between hand dominance and MNCSA in right-handed or left-handed subjects. Conclusion:Hand dominance does not significantly affect MNCSA at the wrist level, and thus does not affect the diagnosis of carpal tunnel syndrome.

Anti-cancer therapeutic agents and carpal tunnel syndrome: Clinical, electrodiagnostic, and ultrasound findings in seven patients.

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy and rarely develops after drug therapy. This study describes the clinical, electrodiagnostic (EDX), and ultrasound (US) findings in seven patients who experienced CTS due to anti-cancer therapeutic agents. All patients underwent EDX testing, and four patients had an US study. CTS occurred in four patients with aromatase inhibitors, two with immune checkpoint inhibitors, and one with a selective estrogen receptor modulator. The mean duration between initiation of the anti-cancer therapeutic agents and symptom onset was 6 weeks (range: 2-12 weeks). Decreased digit sensation was noted in all patients; wasting and weakness of the abductor pollicis brevis (APB) was observed in three (42.8%) patients. The compound muscle action potentials (CMAP) of the APB and sensory nerve action potentials of the second or third digit could not be recorded in two (28.5%) and four (57.1%) patients, respectively. The needle EMG detected fibrillations and positive sharp waves in the APB in two patients. The motor unit potentials of the APB were decreased with large polyphasics in three (42.8%) patients. Of the four patients who underwent US testing, all had increased cross-sectional area of the median nerve at the carpal tunnel inlet, three (75%) had thenar muscle atrophy, and two (50%) had a loss of fascicular pattern. Three (42.8%) patients underwent a CTR. Physicians should be cognizant of the relationship between anti-cancer therapeutic agents and CTS. EDX studies and US play important roles in the diagnostic assessment of such patients.

The effect of anthropometric characteristics and electronic device use on median nerve cross-sectional area: A cross-sectional study

IntroductionThis study aimed to identify the relationship between age, body mass index (BMI), weight, height, and wrist circumference and median nerve cross-sectional area (CSA). The study also aimed to examine the difference between CSA in individuals reporting a high amount (>4 hours per day) of electronic device use compared to those reporting a low amount (≤4 hours per day). Materials/MethodsOne hundred twelve healthy individuals volunteered to participate in the study. Anthropometric, demographic, and self-reported electronic device usage data were collected. A transverse image of the median nerve was captured using ultrasonography from the dominant wrist at the carpal tunnel inlet . A Spearman's rho correlation coefficient was used to examine correlations between participant characteristics (age, BMI, weight, height, and wrist circumference) and CSA. Separate Mann-Whitney U tests were used to examine differences in CSA in those younger and older than age 40, in those with BMI <25 kg/m2 and BMI ≥25 kg/m2, and in high and low-frequency device users. ResultsBMI, weight, and wrist circumference showed fair correlations with CSA. There were significant differences in CSA between individuals younger than 40 and those older than 40 and between individuals with BMI <25kg/m2 and those with BMI ≥25kg/m2. There were no statistically significant differences in CSA in the low- and high-use electronic device groups. DiscussionAnthropometric and demographic characteristics including age and BMI or weight should be considered when examining the CSA of the median nerve, especially when determining cut-off points for establishing a diagnosis of carpal tunnel syndrome.

A "Clear" Carpal Tunnel Syndrome Diagnosis on Ultrasound Examination Does Not Predict Improved Outcomes When Compared With a "Borderline" Diagnosis.

Nerve conduction studies (NCS) and ultrasound (US) remain imperfect compared with clinical diagnosis and/or diagnostic tools such as carpal tunnel syndrome-6 (CTS-6) for diagnosis of carpal tunne syndrome (CTS). One potential reason for the discrepancy between clinical diagnosis and testing is "borderline" case inclusion. This study aims to compare clinical outcomes after carpal tunnel release (CTR) between "borderline" and "clear" patients with CTS determined by NCS and US. This was a retrospective review of patients who underwent CTR. We collected NCS and US measurements of the median nerve cross-sectional area (MNCSA) at the carpal tunnel inlet, and the Boston Carpal Tunnel Questionnaire (BCTQ) scores comprised of the Symptom Severity Scale (SSS) and the Functional Status Scale (FSS). Ultrasound measurements defined patients as having "borderline" (MNCSA < 13 mm2) or "clear" (MNCSA ≥ 13 mm2) CTS. The study included 94 unilateral patients with CTS. "Borderline" CTS was diagnosed in 58 patients (62%), and "clear" CTS was diagnosed in 36 patients (38%). No significant differences in BCTQ scores were found between groups. At greater than 6-month follow-up, the mean FSS was 1.44 and 1.45 for clear and borderline groups, respectively (P = .97) and the mean SSS was 1.47 and 1.51, respectively (P = .84). However, a significant difference between groups when comparing distal motor latency (DML) and distal sensory latency (DSL) existed. The mean DSL was 3.71 and 4.44 for the clear and borderline groups, respectively (P = .02). The mean DML was 4.59 and 5.36 (P = .048). Categorizing CTS diagnosis into "borderline" and "clear" based on preoperative US and NCS testing did not correlate with BCTQ changes after CTR. It remains unclear whether the BCTQ is a valid postoperative assessment tool, despite its frequent use in literature.

Ultrasound and elastography role in pre- and post-operative evaluation of median neuropathy in patients with carpal tunnel syndrome.

Carpal tunnel syndrome (CTS) is a common compression neuropathy of the median nerve in the wrist. Early diagnosis of CTS is essential for selecting treatment options and assessing prognosis. The current diagnosis of CTS is based on the patient's clinical symptoms, signs, and an electromyography (EMG) test. However, they have some limitations. Recently, ultrasound has been adopted as an adjunct diagnostic tool for electromyography (EMG). Ultrasound is a non-invasive and cost-effective technique. It provides a dynamic display of morphological changes in the median nerve and an assessment of CTS etiology such as tenosynovitis, mass compression, and tendon disease. This study aimed to investigate the value of conventional ultrasound and real-time shear wave elastography (SWE) in evaluation of median neuropathy in patients with carpal tunnel syndrome (CTS) before and after surgery. First, the Boston Carpal Tunnel Questionnaire (BCTQ) was administered to patients with CTS. All subjects were measured at three levels: the distal 1/3 of the forearm, the carpal tunnel inlet, and the distal carpal tunnel using conventional ultrasound and SWE. Median nerve parameters were examined in patients with CTS 1 week after surgery. The cross-sectional area (CSA) and stiffness of the median nerve at the carpal tunnel inlet and distal carpal tunnel were significantly higher in patients with CTS than in healthy controls (p < 0.001). The CSA and stiffness of the median nerve at the carpal tunnel inlet were statistically significantly significantly between pre- and postoperative patients with CTS (p < 0.001). The CSA and stiffness of the nerve in patients with CTS had a positive correlation with electrophysiology severity. Conventional ultrasound and elastography are valuable in the diagnosis of CTS and are useful in the clinical assessment of patient's nerve recovery after operation.

Carpal tunnel syndrome in rheumatoid arthritis patients: the role of combined ultrasonographic and electrophysiological assessment

BackgroundCarpal tunnel syndrome (CTS) is known as one of the most common neurological extra-articular manifestations in rheumatoid arthritis (RA) patients. Studies on CTS in RA depend mostly on electrophysiological assessment. Few studies have used ultrasonography for evaluation of the local causes with much focus on wrist arthritis and tenosynovitis as the main cause of entrapment neuropathy of the median nerve in RA. The aim of our study is to assess the local causes of carpal tunnel syndrome in rheumatoid arthritis patients by ultrasonography and whether inflammatory or anomalous variations could affect decision-making and patient management.ResultsCarpal tunnel syndrome was diagnosed in 71 out of 74 examined RA wrists by nerve conduction studies (NCSs) and was categorized from minimal to severe according to Padua et al.’s (Ital J Neurol Sci 18:145–50, 1997) grading criteria. Median nerve CSA at the level of the carpal tunnel inlet and flattening ratio showed statistically significant relation with CTS severity. Bifid MN was found in 20 wrists (10 mild CTS wrists and 10 moderate CTS wrists), a persistent median artery was found in 4 wrists with moderate CTS, and an accessory muscle bundle was present in 3 wrists (2 mild CTS and 1 moderate CTS). The majority of the examined hands (85.1%) showed flexor tendon tenosynovitis at the wrist level and radio-carpal joint synovitis. The US7-joint score using GSUS7 & PDUS7 for synovitis, tenosynovitis and erosions showed significant relation with patients’ disease activity by DAS28 score. Significant relations between CTS severity and the following nerve conduction studies’ parameters, median nerve distal motor latency (DML), motor/sensory NCV, peak sensory latency, amplitude of SNAP, and median-radial latency difference test, were observed.ConclusionSynovial inflammation and local causes of median nerve compression such as bifid median nerve, persistent median artery, and accessory muscle bundle are collectively contributing factors in the etiology of carpal tunnel syndrome in rheumatoid arthritis patients. Ultrasonographic visualization of these inflammatory and anomalous variations enables early detection of CTS and highlights the possibility of non-arthritic-related causes. Using the 7-joint ultrasound (US7) score for assessment of synovitis, tenosynovitis, and erosions in rheumatoid arthritis patients is of valuable role in reflecting inflammation and its relation to the development of CTS in RA patients.

A Novel Ultrasonographic Anthropometric-Independent Measurement of Median Nerve Swelling in Carpal Tunnel Syndrome: The "Nerve/Tendon Ratio" (NTR).

There is little consensus on ultrasound (US) normative values of cross-sectional area of median nerve (MN-CSA) in carpal tunnel syndrome (CTS) because of its dependency on anthropometric parameters. We aim to propose a novel anthropometric-independent US parameter: MN-CSA/flexor radialis carpi CSA (FCR-CSA) ratio ("Nerve Tendon Ratio", NTR), in the diagnosis of clinically and electrodiagnostic (EDS)-defined CTS. 74 wrists of 49 patients with clinically defined CTS underwent EDS (scored by the 1-5 Padua Scale of electrophysiological severity, PS) and US of carpal tunnel with measurement of MN-CSA (at the carpal tunnel inlet), FCR-CSA (over scaphoid tubercle) and its ratio (NTR, expressed as a percentage). US normality values and intra-operator agreement were assessed in 33 healthy volunteers. In controls, the mean MN-CSA was 5.81 mm2, NTR 64.2%. In 74 clinical CTS, the mean MN-CSA was 12.1 mm2, NTR 117%. In severe CTS (PS &gt; 3), the mean MN-CSA was 15.9 mm2, NTR 148%. In CTS, both MN-CSA and NTR correlated with sensitive conduction velocity (SCV) (p &lt; 0.001), distal motor latency (DML) (p &lt; 0.001) and PS (p &lt; 0.001), with a slight superiority of NTR vs. MN-CSA when controlled for height, wrist circumference and weight. In CTS filtered for anthropometric extremes, only NTR maintained a correlation with SCV (p = 0.023), DML (p = 0.016) and PS (p = 0.009). Diagnostic cut-offs were obtained with a binomial regression analysis. In those patients with a clinical diagnosis of CTS, the cut-off of MN-CSA (AUROC: 0.983) was 8 mm2 (9 mm2 with highest positive predictive value, PPV), while for NTR (AUROC: 0.987), the cut-off was 83% (100% with highest PPV). In patients with EDS findings of severe CTS (PS &gt; 3), the MN-CSA (AUROC: 0.876) cut-off was 12.3 mm2 (15.3 mm2 with highest PPV), while for NTR (AUROC: 0.858) it was 116.2% (146.0% with highest PPV). NTR can be simply and quickly calculated, and it can be used in anthropometric extremes.

The Diagnostic Value of the Median Nerve Sonography in Chronic Phase Carpal Tunnel Syndrome Cases in Indonesia

Background. Ultrasound evaluation on the median nerve in carpal tunnel syndrome (CTS) patients by measuring cross-sectional area (CSA) is widely known. However, studies have shown that CSA of the median nerve could vary in different demographical factors. Therefore, the cut-off CSA value for CTS in the Indonesian population could be significantly different. Purpose. To compare mean CSA of the median nerve between normal and CTS populations and establish a cut-off point of CSA to diagnose CTS. Materials and Methods. A comparative cross-sectional study was conducted involving 40 people divided equally into CTS and normal groups. Normal and CTS subjects are determined by Electrodiagnostic study (EDx) using EMG and Nerve Conduction Study (NCS). The CSA measurement was performed at the level of the carpal tunnel inlet. Results. The mean CSA value at the level of tunnel inlet of the normal group was 8.3 ± 1.4 mm2 and for the CTS group is 15.4 ± 4.4 mm2. The receiver operating characteristics (ROC) analysis showed 10.6 mm2 as the cut-off point with 95% sensitivity and 95% specificity (P&lt;0.001). Conclusion. The median nerve CSA at the tunnel inlet is significantly larger in the CTS population and the cut-off point can be recommended in detecting CTS in the Indonesian population.

A deep learning approach to median nerve evaluation in ultrasound images of carpal tunnel inlet

Ultrasound (US) imaging is recognized as a useful support for Carpal Tunnel Syndrome (CTS) assessment through the evaluation of median nerve morphology. However, US is still far to be systematically adopted to evaluate this common entrapment neuropathy, due to US intrinsic challenges, such as its operator dependency and the lack of standard protocols. To support sonographers, the present study proposes a fully-automatic deep learning approach to median nerve segmentation from US images. We collected and annotated a dataset of 246 images acquired in clinical practice involving 103 rheumatic patients, regardless of anatomical variants (bifid nerve, closed vessels). We developed a Mask R-CNN with two additional transposed layers at segmentation head to accurately segment the median nerve directly on transverse US images. We calculated the cross-sectional area (CSA) of the predicted median nerve. Proposed model achieved good performances both in median nerve detection and segmentation: Precision (Prec), Recall (Rec), Mean Average Precision (mAP) and Dice Similarity Coefficient (DSC) values are 0.916 ± 0.245, 0.938 ± 0.233, 0.936 ± 0.235 and 0.868 ± 0.201, respectively. The CSA values measured on true positive predictions were comparable with the sonographer manual measurements with a mean absolute error (MAE) of 0.918 mm2. Experimental results showed the potential of proposed model, which identified and segmented the median nerve section in normal anatomy images, while still struggling when dealing with infrequent anatomical variants. Future research will expand the dataset including a wider spectrum of normal anatomy and pathology to support sonographers in daily practice.Graphical abstract

Localization of the Median Nerve and Flexor Pollicis Longus at the Carpal Tunnel Inlet in Patients With and Without Carpal Tunnel Syndrome Using Ultrasound.

Current illustrations of the carpal tunnel vary greatly. The relative positions of the components such as the median nerve and flexor pollicis longus (FPL) tendon seem often arbitrarily chosen. The purpose of this study was to determine the locations of the median nerve and FPL in the carpal tunnel using ultrasound (US) and to determine whether the position of the median nerve changes in carpal tunnel syndrome (CTS). Patients with and without CTS underwent US examination of the wrist. A 4 × 10 grid was fitted to each saved cross-sectional image. The center points of the median nerve and FPL were identified, and their horizontal and vertical coordinates were recorded. The median nerve was identified in 115 wrists (average x = 0.70, y = 0.82), and FPL was identified in 90 wrists (average x = 0.86, y = 0.59). A scatter plot was created by stacking all US images to demonstrate the average positions of the median nerve and FPL. There were 97 wrists without CTS (No CTS) and 17 wrists with CTS. There was a significant difference in the vertical position of the median nerve between No CTS and CTS wrists (P = .0006). The locations of the median nerve and FPL within the carpal tunnel were determined using US of 115 wrists, and a heat map was created to illustrate these locations. The median nerve was found to be more superficial in the setting of CTS.