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.

Role of multisegmental nerve ultrasound in the diagnosis of leprosy neuropathy.

INTRODUCTION/AIMS: Leprosy is the most common treatable peripheral neuropathy worldwide. The detection of peripheral nerve impairment is essential for its diagnosis and treatment, in order to prevent stigmatizing deformities and disabilities. This study was performed to identify neural thickening through multisegmental ultrasound (US). METHODS: We assessed US measurements of cross-sectional areas (CSAs) of ulnar, median and tibial nerves at two points (in the osteofibrous tunnel and proximal to the tunnel), and also of the common fibular nerve at the fibular head level in 53 leprosy patients (LP), and compared with those of 53 healthy volunteers (HV), as well as among different clinical forms of leprosy. RESULTS: US evaluation detected neural thickening in 71.1% (38/53) of LP and a mean number of 3.6 enlarged nerves per patient. The ulnar and tibial were the most frequently affected nerves. All nerves showed significantly higher measurements in LP compared with HV, and also greater asymmetry, with significantly higher values for ulnar and tibial nerves. We found significant CSAs differences between tunnel and pre-tunnel points for ulnar and tibial nerves, with maximum values proximal to the tunnel. All clinical forms of leprosy evaluated showed neural enlargement through US. DISCUSSION: Our findings support the role of multisegmental US as a useful method for diagnosing leprosy neuropathy, revealing that asymmetry, regional and non-uniform thickening are characteristics of the disease. Furthermore, we observed that neural involvement is common in different clinical forms of leprosy, reinforcing the importance of including US evaluation of peripheral nerves in the investigation of all leprosy patients.

Entrapment of Median Nerve After Pediatric Elbow Dislocation with a Brief Review of Literature: A Case Study.

CASE: We present a case of type II (intraosseous) entrapment of the median nerve in a patient who was diagnosed based on clinical examination and magnetic resonance imaging and who was treated with medial epicondyle osteotomy, neurolysis, and transposition of the nerve to its anatomical position within a month of injury. Our patient made a complete motor and sensory recovery at 5 months with complete functionality and grip strength. CONCLUSION: Median nerve entrapment after posterolateral elbow dislocation is a rare complication with roughly 40 cases reported in the literature. This case illustrates the importance of prompt diagnosis and treatment.

Changes in Ultrasound Parameters of the Median Nerve at Different Positions of the Radiocarpal Joint in Patients with Carpal Tunnel Syndrome.

Ultrasound imaging (US) is being increasingly used to aid in the diagnosis of entrapment neuropathies. This study aims to evaluate the shear modulus and cross-sectional area (CSA) of the median nerve in patients with carpal tunnel syndrome (CTS). A total of 35 patients with CTS participated in the study. CSA and shear modulus testing were performed in shear wave elastography (SWE) mode in five positions of the right and left radiocarpal joints (intermediate position 0°, 45° of extension, maximum extension, 45° of flexion, and maximum flexion). There were significant side-to-side differences in the median nerve shear modulus at each wrist position as compared to the asymptomatic side. There were significant side-to-side differences in the median nerve CSA at each wrist position as compared to the asymptomatic side. Shear modulus increases in patients with CTS at different angular positions of flexion and extension of the radiocarpal joint. In individuals with CTS, the CSA of the median nerve is greater on the symptomatic side compared to the asymptomatic side. The CSA decreases in positions of maximum extension and 45° of flexion and in maximum flexion relative to the resting position.

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.

The median nerve´s system of connective tissue distal to the pronator teres to the carpal tunnel.

BACKGROUND: Connective tissue serves a role beyond mere spatial filling. Furthermore, there is increasing evidence that connective tissue plays an important role in the pathogenesis of conditions such as carpal tunnel syndrome (CTS). According to our hypothesis, the median nerve (MN) is surrounded by a system of connective tissue distal to the pronator teres and extending up to, and including, the carpal tunnel. METHODS: To visualize the connective tissue surrounding the median nerve, we dissected the forearms of 15 body donors from pronator teres to the carpal tunnel, created plastination slices stained with Periodic Acid-Schiff (PAS), and injected ink into the seen spaces. We verified our findings with a segmentational analysis of radiological data of 10 healthy individuals. RESULTS: We macroscopically describe the median nerve´s system of connective tissue (MC) distal to the pronator teres and up to and including the carpal tunnel. This system creates, connects, and separates spaces. At least from the pronator teres to the carpal tunnel it also creates subspaces from proximal to distal. For the MC, we established a mean cross-sectional area of 153.1 mm2 (SD=37.15) in the carpal tunnel. The median nerve consistently resides at the center of this MC, which further connects to flexor muscles of the forearm, and to the radius bone. In the carpal tunnel, the MC creates subspaces inside. There, it also acts as the outermost internal layer enveloping flexor tendons, and the MN. DISCUSSION: The term MC does not negate but orders the existence of other "connectives", like subsynovial connective tissue, endo-, epi- or perineuria, epimysia, periostea, or peritendinea, to a hierarchy related to the median nerve. Diseases of the MN are common. Knowing the anatomy of the MC and how it relates to MN function may help clinicians recognize and understand conditions like CTS.

Fascicular Involvement of the Median Nerve Trunk in the Upper Arm: Manifestation as Anterior Interosseous Nerve Syndrome With Unique Imaging Features.

Selective fascicular involvement of the median nerve trunk above the elbow leading to anterior interosseous nerve (AIN) syndrome is a rare form of peripheral neuropathy. This condition has recently garnered increased attention within the medical community owing to advancements in imaging techniques and a growing number of reported cases. In this article, we explore the topographical anatomy of the median nerve trunk and the clinical features associated with AIN palsy. Our focus extends to unique manifestations captured through MRI and ultrasonography (US) studies, highlighting noteworthy findings, such as nerve fascicle swelling, incomplete constrictions, hourglass-like constrictions, and torsions, particularly in the posterior/posteromedial region of the median nerve. Surgical observations have further enhanced the understanding of this complex neuropathic condition. High-resolution MRI not only reveals denervation changes in the AIN and median nerve territories but also illuminates these alterations without the presence of compressing structures. The pivotal roles of high-resolution MRI and US in diagnosing this condition and guiding the formulation of an optimal treatment strategy are emphasized.

Concurrent spinal and brain imaging with optically pumped magnetometers.

BACKGROUND: The spinal cord and its interactions with the brain are fundamental for movement control and somatosensation. However, brain and spinal electrophysiology in humans have largely been treated as distinct enterprises, in part due to the relative inaccessibility of the spinal cord. Consequently, there is a dearth of knowledge on human spinal electrophysiology, including the multiple pathologies that affect the spinal cord as well as the brain. NEW METHOD: Here we exploit recent advances in the development of wearable optically pumped magnetometers (OPMs) which can be flexibly arranged to provide coverage of both the spinal cord and the brain in relatively unconstrained environments. This system for magnetospinoencephalography (MSEG) measures both spinal and cortical signals simultaneously by employing custom-made scanning casts. RESULTS: We evidence the utility of such a system by recording spinal and cortical evoked responses to median nerve stimulation at the wrist. MSEG revealed early (10 - 15 ms) and late (>20 ms) responses at the spinal cord, in addition to typical cortical evoked responses (i.e., N20). COMPARISON WITH EXISTING METHODS: Early spinal evoked responses detected were in line with conventional somatosensory evoked potential recordings. CONCLUSION: This MSEG system demonstrates the novel ability for concurrent non-invasive millisecond imaging of brain and spinal cord.

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

OBJECTIVES: 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. METHODS: 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). RESULTS: 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). CONCLUSION: 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.

Análisis de los parámetros ecográficos descritos en el estudio del síndrome del túnel del carpo. Una revisión sistemática / Analysis of the echographic parameters described in the study of carpal tunnel syndrome: A systematic review

El síndrome del túnel del carpo (STC) es la mononeuropatía por atrapamiento más frecuente; el diagnóstico se establece mediante pruebas electrodiagnósticas con un número sustancial de falsos positivos/negativos. Presentamos la siguiente revisión sistemática, cuyo objetivo es analizar la literatura más reciente en relación con los parámetros ecográficos descritos para estudiar el STC. Seleccionamos estudios que evaluasen parámetros ecográficos en pacientes con sospecha clínica, siguiendo las recomendaciones del manual Cochrane; incluimos revisiones sistemáticas, metaanálisis, estudios caso-control y de pruebas diagnósticas, valorando estudios retrospectivos y revisiones bibliográficas con buena calidad metodológica. La revisión se hizo de artículos publicados entre 2005-2019. Incluimos 8 artículos (2 revisiones sistemáticas/metaanálisis, 2 estudios caso-control, un estudio de pruebas diagnósticas, 2 revisiones literarias y un estudio retrospectivo). Los parámetros analizados fueron el área de sección transversa del nervio mediano, el índice muñeca-antebrazo, el índice entrada-salida, el rango de adelgazamiento del nervio mediano, el abombamiento del retináculo flexor y la vascularización/movilidad. La evidencia actual permite afirmar que la ecografía tiene utilidad en el cribado del STC.(AU)

Carpal tunnel syndrome (CTS) is the most common entrapment mononeuropathy; the diagnosis is established by electrodiagnostic tests with until 34% of false positives/negatives. We present the following systematic review which objective is to analyze the most recent literature related to the ultrasound parameters described to study CTS. We selected studies that evaluated ultrasound parameters in patients with clinical suspicion following the Cochrane manual's recommendations. We include systematic reviews, meta-analyses, case–control studies and diagnostic tests, evaluating retrospective studies and bibliographic reviews with proper methodological quality. Articles published between 2005 and 2019. We included eight articles (two systematic reviews/meta-analyses, two case–control studies, one diagnostic test study, two literature reviews, and one retrospective). The parameters analyzed were cross-sectional area, wrist–forearm index, entry–exit index, thinning range, palmar bowing of the flexor retinaculum, and vascularity/mobility. Current evidence allows us to affirm that ultrasound is useful in screening for CTS.(AU)

Lipofibromatous Hamartoma of the Median Nerve - A Rare Condition in the Hand.

Lipofibromatous hamartoma (LFH) of the median nerve is a rare condition in the hand and often remains asymptomatic for a significant period. MRI imaging can reveal unique tumour characteristics; however, the definitive diagnosis is confirmed through a tissue biopsy. In this report, a 38-year-old male presented with a gradually growing mass on his right hand. Physical examination revealed a large soft tissue mass extending from the thenar area to the wrist, causing compression of the median nerve. MRI confirmed the presence of a distinct soft tissue mass on the volar side of the hand. The mass was excised along with a fascicle and confirmed by histological examination. One year after surgery, sensation has improved, but weakness remains and opponensplasty was offered to the patient. Although the treatment strategy of LFH of the median nerve remains controversial, delayed treatment can result in severe compressive neuropathy and irreversible nerve damage. Level of Evidence: Level V (Therapeutic).

Identifying anatomic landmarks and median nerve characteristics for the analysis of persistent carpal tunnel syndrome using magnetic resonance imaging (MRI).

OBJECTIVE: Carpal tunnel syndrome (CTS) is the most common nerve entrapment neuropathy in the USA. In this study, we define anatomical landmarks to assess symptomatic and asymptomatic cohorts with persistent CTS using MRI imaging. MATERIALS AND METHODS: Distal vs proximal incomplete release was determined using the distal most aspect of the hook of hamate and the distal wrist crease. An incomplete release showed the transverse carpal ligament (TCL) intact at either boundary. Twenty-one patients with persistent CTS were analyzed for incomplete release, median nerve enlargement and T2 signal hyperintensity, and flattening ratio using postoperative wrist MRI. These findings were compared to a ten-patient asymptomatic persistent CTS control group. Fisher's exact and a Student's two-tailed t-tests were used to determine statistical significance. RESULTS: In the symptomatic persistent CTS group, 13 (61.9%) incomplete releases were identified, 5 (38.5%) incomplete distally, and 1 (7.7%) incomplete proximally. There was no statistical significance in the rate of incomplete releases when compared to the asymptomatic group (p = 1.00). T2 signal hyperintensity and enlargement at the site of release showed no statistical significance, (p = 0.319 and p = 0.999, respectively). The mean flattening ratio at the site of release in the symptomatic group (2.45 ± 0.7) was statistically significant compared to the asymptomatic group (1.48 ± 0.46), (p = 0.007). CONCLUSION: Utilizing the established landmarks, the full length of the TCL can be assessed via MRI. Additionally, evaluation of the median nerve flattening ratio at the level of the incomplete release may be utilized as an aid to the clinical management of persistent CTS.

Utility of shear wave elastography for diagnosing carpal tunnel syndrome with psoriatic arthritis.

BACKGROUND: Carpal tunnel syndrome (CTS) is a type of peripheral entrapment neuropathy and common for the patients with psoriatic arthritis (PsA). Shear wave elastography (SWE) is a new ultrasonography technique that can be used for diagnosing CTS, but not studied in PsA patients. AIMS: The aim of this study to measure the stiffness of median nerve and hand muscles by quantitative SWE to identify whether SWE can be used for diagnosing CTS in patients with PsA or not. METHODS: To diagnose CTS, all patients had electrodiagnostic study. The stiffness values of the median nerve, abductor pollicis brevis, and abductor digiti minimi were determined using SWE. Muscle stiffness ratio was also calculated. RESULTS: Consideration is given to 48 patients with PsA (93 wrists) and 29 healthy volunteers (57 wrists). Median nerve stiffness was found to be significantly higher, and abductor pollicis brevis' stiffness and muscle stiffness ratio were significantly lower in PsA patients' wrists compared to control group (p = 0.002, p < 0.001, p = 0.001, respectively) and in CTS wrists compared to others (p < 0.001, p < 0.001, p = 0.001, respectively). Receiver operating characteristic analysis identified 28.2 kPA as the median nerve stiffness cut-off point for differentiating CTS in PsA patients (p = 0.001). CONCLUSIONS: We found that SWE has a good diagnostic value for CTS with PsA patients; hence, we can conclude that SWE could diagnose CTS in PsA patients.

Nerve sonography in the diagnostic evaluation of primary and secondary carpal tunnel syndrome in rheumatoid arthritis.

BACKGROUND AND PURPOSE: Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy and extra-articular manifestation of rheumatoid arthritis (RA). However, in patients with RA, it is not always possible to clinically distinguish an actual CTS from other RA-based complaints. METHODS: We evaluated the diagnostic role of nerve ultrasound (NUS) as supportive tool in the diagnostic process of CTS in patients with RA and tried to provide etiological clarification in cases of secondary CTS. Fifty-eight patients with RA and clinical suspicion of CTS were enrolled. All patients underwent a standardized clinical-neurological, electrophysiological (nerve conduction studies [NCS]), and NUS examination and completed the Boston CTS Questionnaire (BCTQ). RESULTS: In 96 of 116 hands examined, a clinical suspicion of CTS was documented. In 43 of 96 (44.8%) CTS-positive hands, the diagnosis was primarily confirmed by NCS, whereas in another 16 of 96 (30.2%) hands, the diagnosis could only be verified by NUS, leading to a diagnosis of CTS in 59 of 116 (50.8%) hands. In 19 of 59 (32.3%) CTS-positive hands, tenosynovial hypertrophy was observed, and in 7 of 59 (11.8%), a cystic mass was identified as the underlying cause of secondary CTS. A good correlation between NCS and NUS findings was documented, but no significant correlation was found between NCS, NUS, and clinical findings/BCTQ. CONCLUSIONS: In people with RA, a diagnosis of CTS purely on a clinical basis is nonspecific and should be supported by NCS and/or NUS. NUS markedly facilitates the diagnosis of CTS in these patients and enables differentiation between primary and secondary causes.

Transformer-Based Automated Segmentation of the Median Nerve in Ultrasound Videos of Wrist-to-Elbow Region.

Segmenting the median nerve is essential for identifying nerve entrapment syndromes, guiding surgical planning and interventions, and furthering understanding of nerve anatomy. This study aims to develop an automated tool that can assist clinicians in localizing and segmenting the median nerve from the wrist, mid-forearm, and elbow in ultrasound videos. This is the first fully automated single deep learning model for accurate segmentation of the median nerve from the wrist to the elbow in ultrasound videos, along with the computation of the cross-sectional area (CSA) of the nerve. The visual transformer architecture, which was originally proposed to detect and classify 41 classes in YouTube videos, was modified to predict the median nerve in every frame of ultrasound videos. This is achieved by modifying the bounding box sequence matching block of the visual transformer. The median nerve segmentation is a binary class prediction, and the entire bipartite matching sequence is eliminated, enabling a direct comparison of the prediction with expert annotation in a frame-by-frame fashion. Model training, validation, and testing were performed on a dataset comprising ultrasound videos collected from 100 subjects, which were partitioned into 80, ten, and ten subjects, respectively. The proposed model was compared with U-Net, U-Net++, Siam U-Net, Attention U-Net, LSTM U-Net, and Trans U-Net. The proposed transformer-based model effectively leveraged the temporal and spatial information present in ultrasound video frames and efficiently segmented the median nerve with an average dice similarity coefficient (DSC) of approximately 94% at the wrist and 84% in the entire forearm region.

Elevated intraneural vascularization of the median nerve proximal to the arteriovenous fistula in hemodialysis patients suspected of carpal tunnel syndrome: A case series.

Patients with end-stage kidney disease may require creation of an arteriovenous fistula in order to receive hemodialysis treatment. The creation may result in several complications, including carpal tunnel syndrome. Early diagnosis and treatment are essential to relieve symptoms, prevent permanent nerve damage, and improve quality of life. However, the sensory and motor disturbances resembling carpal tunnel syndrome could be related to other etiologies than external compression of the median nerve underneath the transverse ligament. This case report presents eight patients with a radiocephalic arteriovenous fistula, who all had symptoms of carpal tunnel syndrome. Ultrasonographic examination showed a segmental intraneural hypervascularization of a large vessel inside the median nerve proximal to the wrist and arteriovenous fistula anastomosis with garland-like course as well as multiple flow velocities. The neurophysiological findings showed a significant decreased velocity in the ipsilateral forearm to the arteriovenous fistula.

Volume Effect of Nerve Hydrodissection for Carpal Tunnel Syndrome: A Prospective, Randomized, and Single-Blind Study.

OBJECTIVES: This study compared ultrasound-guided nerve hydrodissection (HD) outcomes using two commonly used injectate volumes (10 and 5 mL) of normal saline to explore if there is a volume effect of HD for patients with moderate carpal tunnel syndrome (CTS). METHODS: Twenty-four participants were randomly assigned to treatment with HD using ultrasound-guidance and either 10 mL or 5 mL of normal saline (HD-10 and HD-5 groups respectively). Our primary outcome measures were the change scores of the two subscales of the Boston Carpal Tunnel Syndrome Questionnaire: The Symptom Severity Scale (SSS) and Functional Status Scale (FSS). We conducted a one-way repeated analysis of variance for 3 time points (4, 12, and 24 weeks) for both SSS and FSS, respectively, for change scores from time 0, and percentage change from time 0. RESULTS: All participants (n = 12 per group) completed the study. From 0 to 24 weeks the HD-10 group outperformed the HD-5 group for improvement in SSS (median ± IQR; -0.8 ± 0.4 versus -0.5 ± 0.5; P = .024) and FSS scores (mean ± SD; -0.8 ± 0.2 versus -0.5 ± 0.5; P = .011). The HD-10 group improvement in FSS subtest significantly exceeded the MCID percentage-change-based threshold of 27% (34%; P = .039). CONCLUSIONS: Despite the limitations of small study size, a largely inert injectate, and a single injection approach, these findings in favor of the 10 mL group suggest that the volume used for ultrasound-guided HD in moderate CTS matters, and a higher volume is more effective.

[Analysis of the echographic parameters described in the study of carpal tunnel syndrome: A systematic review]. / Análisis de los parámetros ecográficos descritos en el estudio del síndrome del túnel del carpo. Una revisión sistemática.

Carpal tunnel syndrome (CTS) is the most common entrapment mononeuropathy; the diagnosis is established by electrodiagnostic tests with until 34% of false positives/negatives. We present the following systematic review which objective is to analyze the most recent literature related to the ultrasound parameters described to study CTS. We selected studies that evaluated ultrasound parameters in patients with clinical suspicion following the Cochrane manual's recommendations. We include systematic reviews, meta-analyses, case-control studies and diagnostic tests, evaluating retrospective studies and bibliographic reviews with proper methodological quality. Articles published between 2005 and 2019. We included eight articles (two systematic reviews/meta-analyses, two case-control studies, one diagnostic test study, two literature reviews, and one retrospective). The parameters analyzed were cross-sectional area, wrist-forearm index, entry-exit index, thinning range, palmar bowing of the flexor retinaculum, and vascularity/mobility. Current evidence allows us to affirm that ultrasound is useful in screening for CTS.

Time-varying changes in median nerve deformation and position in response to quantified pinch and grip forces.

The ability of the median nerve (MN) to adapt in response to altered carpal tunnel conditions is important to mitigate compressive stress on the nerve. We assessed changes in MN deformation and position throughout the entire time course of hand force exertions. Fourteen right-handed participants ramped up force from 0% to 50% of maximal voluntary force (MVF) before ramping force back down in three different hand force exertion tasks (pulp pinch, chuck pinch, power grip). Pinch and grip forces were measured with a digital dynamometer, which were time synchronized with transverse carpal tunnel images obtained via ultrasound. Ultrasound images were extracted in 10% increments between 0% and 50% MVF while ramping force up (loading phase) and down (unloading phase). MN deformation and position relative to the flexor digitorum superficialis tendon of the long finger were assessed in concert. During loading, the nerve became more circular while displacing dorsally and ulnarly. These changes primarily occurred at the beginning of the hand force exertions while ramping force up from 0% to 20%, with very little change between 20% and 50% MVF. Interestingly, deformation and position changes during loading were not completely reversed during unloading while ramping force down. These findings indicate an initial reorganization of carpal tunnel structures. Mirrored changes in nerve deformation and position may also reflect strain-related characteristics of adjoining subsynovial connective tissue. Regardless, time-varying changes in nerve deformation and position appear to be an important accommodative mechanism in the healthy carpal tunnel in response to gripping and pinching tasks.

Assessment of the carpal tunnel and associated neural structures with superb microvascular imaging: a scoping review.

INTRODUCTION: Superb microvascular imaging (SMI) is an advanced ultrasound technique that portrays microcirculation. Its clinical applications have been studied in various diseases, including carpal tunnel syndrome (CTS) i.e. the most common entrapment neuropathy. This scoping review explores the role of SMI in diagnosing CTS or the assessment of relevant neural structures. METHODS: We conducted a comprehensive search of electronic databases (PubMed, Embase and Web of Science) up to 26 September 2023. Two independent authors conducted the literature search, quality assessment, and data extraction. RESULTS: This review includes seven studies comprising 385 wrists. SMI consistently revealed increased intraneural vascularity in the median nerves of patients with CTS compared to healthy individuals. While SMI demonstrated higher sensitivity than traditional Doppler methods for detecting CTS, its specificity was somewhat lower. Combining SMI with B-mode ultrasound appears to enhance the diagnostic accuracy for CTS. However, the relationship between SMI findings and CTS severity remains unclear. CONCLUSIONS: This review highlighted the ability of SMI to provide detailed vascular structures in both healthy wrists and those with CTS. Additional research is crucial to determine the typical SMI findings of the carpal tunnel and within that context, tailor more precise diagnostic/therapeutic applications for the CTS population.