Combined Doppler and B-mode sonography in carpal tunnel syndrome

Advances in Imaging of Compressive Neuropathies

Ultrasound and magnetic resonance neurography are useful modalities to aid in the assessment of compressive neuropathies, although they are still limited in their resolution of nerve microstructure and their capacity to monitor postoperative nerve recovery. Optical coherence tomography, a preclinical imaging modality, is promising in its ability to better identify structural and potential physiologic changes to peripheral nerves, but requires additional testing and research prior to widespread clinical implementation. Further advances in nerve imaging may elucidate the ability to visualize the zone of nerve injury intraoperatively, monitor the progression of nerve regeneration, and localize problems during nerve recovery.

Future Considerations in the Diagnosis and Treatment of Compressive Neuropathies of the Upper Extremity

Compressive neuropathies of the upper extremity are among the most common conditions seen by hand surgeons. The diagnoses of carpal tunnel syndrome and cubital tunnel syndrome have traditionally been made by a combination of history, physical examination, and electrodiagnostic testing. However, findings can be nonspecific and electrodiagnostic testing is invasive for the patient. The diagnosis of compressive neuropathies continues to evolve as technology advances, and newer diagnostic modalities predominantly focus on preoperative diagnostic imaging with ultrasound and magnetic resonance imaging/neurography. With the advent of cheaper, faster, and less invasive imaging, the future may bring a paradigm shift away from electrophysiology as the gold standard for the preoperative diagnosis of compressive neuropathies. Intraoperative imaging of nerve health is an emerging concept that warrants further investigation, whereas postoperative imaging of nerve recovery with ultrasound and magnetic resonance imaging currently has a limited role because of nonspecific findings and potential for misinterpretation. Advances in surgical treatment of compressive neuropathies appear to center around the use of imaging for less invasive neurolysis techniques and other adjunctive treatments with nerve decompression. The management of failed peripheral nerve decompressions and recurrent compressive neuropathies remains challenging.

Thirty Minutes of Sub-diastolic Blood Flow Occlusion Alters Carpal Tunnel Tissue Function and Mechanics

There is evidence that carpal tunnel syndrome (CTS) development is driven by vascular factors, specifically those resulting from ischemia and edema. The purpose of this study was to investigate the vascular hypothesis of CTS development by quantifying the temporal effects of 30 min of sub-diastolic brachial blood flow occlusion on median nerve edema, intraneural blood flow velocity, nerve function as measured through nerve conduction study (NCS), tendon-connective tissue mechanics and carpal tunnel tissue stiffness. Forty healthy volunteers underwent 30 min of sub-diastolic brachial occlusion while an NCS and ultrasound examination were performed consecutively every 5 min. Motor latency (p < 0.001), sensory conduction velocity (p < 0.001), sensory amplitude (p = 0.04), nerve blood flow (p < 0.001), peak relative flexor digitorum superficialis tendon-sub-synovial connective tissue displacement (p = 0.02) and shear strain (p = 0.04) were significantly affected by partial ischemia. Our results highlight the dependency of carpal tunnel tissue function on adequate blood flow.

Harnessing the 2D Structure-Enabled Viscoelasticity of Graphene-Based Hydrogel Membranes for Chronic Neural Interfacing

Stiffness and viscoelasticity of neural implants regulate the foreign body response. Recent studies have suggested the use of elastic or viscoelastic materials with tissue-like stiffness for long-term neural electrical interfacing. Herein, the authors find that a viscoelastic multilayered graphene hydrogel (MGH) membrane, despite exhibiting a much higher Young's modulus than nerve tissues, shows little inflammatory response after 8-week implantation in rat sciatic nerves. The MGH membrane shows significant viscoelasticity due to the slippage between graphene nanosheets, facilitating its seamless yet minimally compressive interfacing with nerves to reduce the inflammation caused by the stiffness mismatch. When used as neural stimulation electrodes, the MGH membrane can offer abundant ion-accessible surfaces to bring a charge injection capacity 1-2 orders of magnitude higher than its traditional Pt counterpart, and further demonstrates chronic neural therapy potential in low-voltage modulation of rat blood pressure. This work suggests that the emergence of 2D nanomaterials and particularly their unique structural attributes can be harnessed to enable new bio-interfacing design strategies.

Diagnostic Utility of Superb Microvascular Imaging and Power Doppler Ultrasonography for Visualizing Enriched Microvascular Flow in Patients With Carpal Tunnel Syndrome

Recent studies suggest that blood flow changes in the median nerve may help confirm a diagnosis of carpal tunnel syndrome (CTS). Herein, we examined the utility of superb microvascular imaging (SMI), a new ultrasonographic (US) technique for visualizing microvascular flow, for detecting blood flow differences between CTS patients and healthy controls. We performed a retrospective analysis of 28 hands with suspected CTS. Patients received both nerve conduction and US examinations. Ten healthy volunteers were enrolled as the control group. The nerve compression ratio and the blood flow signal area were quantified using color Doppler US (CDUS), power Doppler US (PDUS), and SMI. Correlation analyses between the blood flow signal area, the compound muscle action potential of the thenar muscle, and the nerve compression ratio were performed. As a result, the mean nerve compression ratio was found to be significantly higher in the CTS group. There were no differences in the blood flow signal area between the groups using CDUS, while PDUS and SMI showed higher blood flow signals in the CTS group. The blood flow signal area measured by SMI had stronger correlations with the compound muscle action potential amplitude and the nerve compression ratio than those for PDUS. The diagnostic utility of SMI was equivalent to PDUS, but superior to conventional CDUS. Nevertheless, the blood flow signal by SMI was more strongly correlated with the electrophysiological severity and compression ratio than for PDUS. Use of SMI in future studies may help clarify the underlying mechanisms of blood flow changes in CTS.

Sonographic Diagnosis of Carpal Tunnel Syndrome

Diagnostic ultrasound in the diagnosis of carpal tunnel syndrome is firmly established. Preoperative evaluation is based on quantitative parameters such as measurement of the pathologically enlarged cross-sectional area of the nerve. The value of postoperative ultrasound lies in the visualization of the anatomy and the conclusions that can be drawn from it. It focuses on the semiquantitative sonographic parameters of nerve compression. Nerve lesions and persistent strictures can be visualized and clearly localized. In recurrent disease, the primary focus is to dynamically exclude postoperative scarring, which results in a reduction of nerve gliding.

Influence of temperature on sonographic images of the median nerve for the diagnosis of carpal tunnel syndrome: a case control study

Background

In addition to nerve conduction studies (NCSs), ultrasonography has been widely used as an alternative tool for diagnosing carpal tunnel syndrome (CTS). Although the results of NCSs are influenced by local skin temperature, few studies have explored the effects of skin temperature on ultrasonography of the median nerve. Since swelling and intraneural blood flow of the median nerve might be influenced by local temperature changes, the aim of this study was to evaluate the cross-sectional area (CSA) and intraneural blood flow of the median nerve under three skin temperatures (30 °C, 32 °C, 34 °C).

Methods

Fifty patients with CTS and 50 healthy volunteers were consecutively recruited from a community hospital. Each participant received physical examinations and NCSs and underwent ultrasonography, including power Doppler, to evaluate intraneural vascularity.

Results

The CSA of the median nerve in the CTS patients was significantly larger than that in the healthy controls at all three temperatures. However, significant differences in the power Doppler signals of the median nerve between the two studied groups were observed only at 30 and 32 °C, not at 34 °C.

Conclusion

The significant difference in the intraneural vascularity of the median nerve between the patients with CTS and the healthy subjects was lost at higher temperatures (34 °C). Therefore, the results of power Doppler ultrasonography in diagnosing CTS should be cautiously interpreted in patients with a high skin temperature or those who reside in warm environments.

Diagnosis of Carpal Tunnel Syndrome using Shear Wave Elastography and High-frequency Ultrasound Imaging

OBJECTIVES

The performance of ultrasound features from shear wave elastography (SWE) and high-frequency ultrasound imaging was evaluated independently and in combination to diagnose carpal tunnel syndrome (CTS).

MATERIALS AND METHODS

Twenty-five subjects were imaged in a sitting position with an arm extended and palm facing up. SWE of the medial nerve (MN) was acquired at the wrist level (site 1) and proximal to the pronator quadratus muscle (site 2). Cross-sectional area (CSA) and vascularity of the MN were assessed at the wrist using a 24 MHz probe. Color and power Doppler imaging (CDI and PDI), monochrome and color-coded Superb Microvascular Imaging (SMI) were performed for vascularity assessments. The diagnosis and severity of CTS was determined by clinical and electrodiagnostic tests. Diagnostic performance of the ultrasound features was assessed by t-tests, ANOVAs, and ROC analysis.

RESULTS

The study included 20 control hands and 27 hands with CTS. All ultrasound features except for the stiffness ratio were significantly different between the CTS and control wrists (p<0.04). The stiffness of MN at site 1 showed a higher accuracy than at site 2. The combination of CSA and MN stiffness from site 2 showed an overall accuracy of 95% with a specificity and sensitivity of 100% and 93%, respectively. The CSA, MN stiffness from site 2, and CDI combination improved the accuracy to 96% with specificity and sensitivity of 100% and 93%, respectively. However, no ultrasound features (independently or in combination) differentiated all stages of CTS severity.

CONCLUSIONS

SWE with high-frequency ultrasound imaging showed potential for the diagnosis of CTS.

Quantitative assessment of intraneural vascular alterations in peripheral nerve trauma using high-resolution neurosonography: technical note

High-resolution neurosonography (HRNS) has become a major imaging modality in assessment of peripheral nerve trauma in the recent years. However, the vascular changes of traumatic lesions have not been quantitatively assessed in HRNS. Here, we describe the vascular-ratio, a novel HRNS-based quantitative parameter for the assessment of intraneural vascular alterations in patients with nerve lesions. N = 9 patients suffering from peripheral nerve trauma were examined clinically, electrophysiologically and with HRNS (SonoSite Exporte, Fuji). Image analyses using Fiji included determination of the established fascicular ratio (FR), the cross-section ratio (CSR), and as an extension, the calculation of a vascular ratio (VR) of the healthy versus damaged nerve and a muscle perfusion ratio (MPR) in comparison to a healthy control group. The mean VR in the healthy part of the affected nerve (14.14%) differed significantly (p < 0.0001) from the damaged part (VR of 43.26%). This coincides with significant differences in the FR and CSR calculated for the damaged part versus the healthy part and the controls. In comparison, there was no difference between VRs determined for the healthy part of the affected nerve and the healthy controls (14.14% / 17.72%). However, the MPR of denervated muscles was significantly decreased compared to the non-affected contralateral controls. VR and MPR serve as additional tools in assessing peripheral nerve trauma. Image analysis and calculation are feasible. Combined with the more morphologic FR and CSR, the VR and MPR provide a more detailed insight into alterations accompanying nerve trauma.

Effect of Force, Posture, and Repetitive Wrist Motion on Intraneural Blood Flow in the Median Nerve

OBJECTIVES

Pinching, deviated wrist postures, and repetitive motion are risk factors for carpal tunnel syndrome. Hypervascularization of the median nerve and increased intraneural blood flow proximal to the carpal tunnel result in finger force and deviated wrist postures. The purpose of this study was to determine the effects of pinching with and without force, wrist posture, and repetitive wrist motion on intraneural blood flow in the median nerve.

METHODS

Eleven healthy and 11 carpal tunnel syndrome-symptomatic individuals completed 3 sections of this study: 15 pinch posture force trials, 3 repetitive wrist motion trials, and 3 static wrist posture trials. Intraneural blood flow (centimeters per second) was measured with pulsed wave Doppler ultrasound during each trial. Transverse B-mode images obtained from static trials were used to calculate the median nerve cross-sectional area and circumference.

RESULTS

An analysis of variance statistical analysis revealed significant main effects of pinch posture force (F_4,80 = 21.397; P < .001) and wrist posture (F_2,40 = 14.545; P < .001). Intraneural blood flow velocities were significantly greater when 6 N of force was applied by the thumb, finger, or pinch compared to no applied force in the same postures. Intraneural blood flow velocities were higher at 30° wrist flexion (mean ± SD, 2.24 ± 0.42 cm/s) than neutral (2.06 ± 0.45 cm/s) and 30° wrist extension (1.97 ± 0.46 cm/s). No changes were found in response to repetitive wrist motion.

CONCLUSIONS

Flexed wrists as well as applied finger and thumb forces increase median nerve blood flow at the entry to the carpal tunnel, which may negatively affect the median nerve.

Superb microvascular imaging for detecting carpal tunnel syndrome compared with power Doppler ultrasonography: A protocol for systematic review and meta-analysis

BACKGROUND

Sonography enhances diagnostic accuracy by the detection of the epineural or intraneuronal blood flow.[1-4] Power Doppler ultrasonography (PDUS) in carpal tunnel syndrome (CTS) has been previously studied and shown to be valid and reliable for grading the intraneural flow.[3,4] However, superb microvascular imaging (SMI) represents a new era in diagnostic sonography, and this new technology enables accurate visualization of vascular structures with intensive clutter suppression to provide flow signals for large to small vessels, and it presents these data at high frame rates.[5-7] Studies suggested that SMI is more sensitive in demonstrating blood flow in the diagnosis of CTS compared with PDUS.[7] In order to gain clarity, a meta-analysis to systematically review and synthesize relevant data on the evaluating intraneural blood flow of the median nerve (MN) using SMI and PDUS was undertaken.

METHODS

We will search PubMed, Web of Science, Cochrane Library, and Chinese biomedical databases from their inceptions to the December 31, 2020, without language restrictions. Two authors will independently carry out searching literature records, scanning titles and abstracts, full texts, collecting data, and assessing risk of bias. Review Manager 5.2 and Stata 14.0 software will be used for data analysis.

RESULTS

This systematic review will investigate whether superb microvascular imaging is more sensitive to display the blood flow in the MN with CTS than PDUS.

CONCLUSION

Its findings will provide strong evidence for the feasibility of superb microvascular imaging on the detection of the neovascularization of the MN with CTS.

SYSTEMATIC REVIEW REGISTRATION

INPLASY202110018.

Ultrasound examination predicts 6-month progression in carpal tunnel syndrome patients

Carpal tunnel syndrome (CTS) is a peripheral neuropathy resulting from chronic median nerve compression. Chronic compression leads to neurological changes that are quantified through nerve conduction studies (NCS). Although NCS represents the gold standard in CTS assessment, they provide limited prognostic value. Several studies have identified ultrasound as a tool in diagnosing and potentially predicting the progression of CTS in patients. The purpose of this study was to evaluate the predictive value of ultrasound examination in CTS patients. Twenty patients recruited at their first visit with the neurologist completed two NCS and ultrasound examinations approximately 6 months apart. Ultrasound examination consisted of B-mode, pulse-wave Doppler and colour Doppler ultrasound videos and images to quantify median nerve cross-sectional area, intraneural blood flow velocity in three wrist postures (15° flexion, neutral, and 30° extension), and displacement of the flexor digitorum superficialis (FDS) tendon and the adjacent subsynovial connective tissue (SSCT) of the middle finger during repetitive finger flexion-extension cycles. A questionnaire was administered to assess the work-relatedness of CTS. Linear regression analyses revealed that intraneural blood flow velocity (R²  = 0.36, p = .03), assessed in wrist flexion, and relative FDS-SSCT displacement (R²  = 0.27, p = .04) and shear strain index (R²  = 0.28, p = .04) were significant predictors of nerve sensory and motor changes at 6 months. Results suggest the possibility of using a battery of ultrasound measures as viable markers to predict median nerve functional changes within 6 months.

Advanced Musculoskeletal Ultrasound Techniques: What Are the Applications?

OBJECTIVE. The purpose of this article is to cover technical advances in musculo-skeletal ultrasound from the viewpoint of the radiologist. CONCLUSION. Among the advances in musculoskeletal ultrasound that we highlight the use of ultrahigh-frequency transducers to visualize ever-finer anatomic detail, the expanding practical clinical applications for microvascular imaging, and the use of elastography to predict function and, possibly, healing potential.

Current and future applications of ultrasound imaging in peripheral nerve disorders

Neuromuscular ultrasound (NMUS) is a rapidly evolving technique used in neuromuscular medicine to provide complimentary information to standard electrodiagnostic studies. NMUS provides a dynamic, real time assessment of anatomy which can alter both diagnostic and management pathways in peripheral nerve disorders. This review describes the current and future techniques used in NMUS and details the applications and developments in the diagnosis and monitoring of compressive, hereditary, immune-mediated and axonal peripheral nerve disorders, and motor neuron diseases. Technological advances have allowed the increased utilisation of ultrasound for management of peripheral nerve disorders; however, several practical considerations need to be taken into account to facilitate the widespread uptake of this technique.

Blood flow velocity but not tendon mechanics relates to nerve function in carpal tunnel syndrome patients

Carpal tunnel syndrome (CTS) develops from chronic compression of the median nerve. Chronic compression results in a number of vascular, structural and functional changes to the carpal tunnel tissues which ultimately manifest in the characteristic symptoms of CTS. The purpose of this study was to investigate the interplay of median nerve function, median nerve hemodynamics, and finger flexor tendon and subsynovial connective tissue (SSCT) mechanics in CTS patients. Thirty-five patients were recruited following nerve conduction study for this double-blinded imaging study. Ultrasound B-mode, pulse-wave Doppler, and colour Doppler images and videos were collected at the proximal carpal tunnel to quantify: (1) median nerve cross-sectional area, (2) intraneural blood flow velocity in 3 wrist postures (neutral (0°), flexion (15°), extension (30°)), and (3) flexor digitorum superficialis and SSCT displacement. Results demonstrate that intraneural blood flow velocity is dependent on median nerve function and wrist posture such that patients with mild CTS are more susceptible to the effects of non-neutral wrist postures. Tendon-SSCT mechanics do not appear to differ based on severity. This study stresses the importance of limiting exposure to non-neutral wrist postures in patients with early signs of the condition.

Clinical Applications of Superb Microvascular Imaging in the Liver, Breast, Thyroid, Skeletal Muscle, and Carotid Plaques

This article reviews the clinical applications of Superb Microvascular Imaging (SMI; Canon Medical Systems, Otawara, Japan) in the liver, breast, thyroid, skeletal muscle, and carotid plaques. Diseases that are closely associated with angiogenesis can be diagnosed by SMI in a relatively early phase, and using SMI can prevent adverse reactions associated with the contrast agents used in contrast-enhanced ultrasound. Super Microvascular Imaging also shows particular value in grading disease activities and monitoring therapeutic responses. Although SMI has some limitations, such as a lack of clinical standards, it can add information to conventional ultrasound examinations and may become a noninvasive alternative to invasive diagnostic procedures for many clinical conditions.

Superb Microvascular Imaging of the Median Nerve in Carpal Tunnel Syndrome: An Electrodiagnostic and Ultrasonographic Study

OBJECTIVE

To evaluate intraneural blood flow of the median nerve using superb microvascular imaging (SMI) and power Doppler ultrasonography (PDUS), and to examine their correlation with electroneuromyography in patients with carpal tunnel syndrome (CTS).

METHODS

A cross-sectional survey was used, and the study was conducted in the research unit of a training and research hospital. Patients diagnosed with CTS according to electroneuromyography studies were included in the study. Ultrasound measurements were taken using an Aplio-500 (Toshiba Medical System Corporation, Tokyo, Japan) device and a linear multifrequency 14-MHz probe. The cross-sectional area of the median nerve at the carpal tunnel level was measured by the direct tracing method using electronic calipers. The power Doppler ultrasonography and superb microvascular imaging scores were recorded by grading the vascularity between 0 and 3.

RESULTS

Evaluation was made of a total of 113 hands of 80 patients (18 men, 62 women) with a mean age of 34.67 ± 12.82 years. The mean duration of symptoms was 12.34 ± 6.66 months. When the patients were grouped as mild, moderate, and severe CTS, there was a statistically significant difference between the SMI and PDUS grades (P < .05). As the severity of CTS increased, an increase in SMI and PDUS scores was observed. There was a strong correlation between SMI scores and motor distal latency (r = .71/P = .026), amplitude of sensory action potential (r = -.77/P = .029), and sensory neurotransmission rate (r = .77/P = .029).

CONCLUSION

SMI seems to be more sensitive than PDUS for evaluating the vascularity of the median nerve in patients with CTS, and SMI grading is correlated with the ENMG results.

Blood Flow Changes in Subsynovial Connective Tissue on Contrast-Enhanced Ultrasonography in Patients With Carpal Tunnel Syndrome Before and After Surgical Decompression

OBJECTIVES

Although qualitative alteration of the subsynovial connective tissue in the carpal tunnel is considered to be one of the most important factors in the pathophysiologic mechanisms of carpal tunnel syndrome (CTS), little information is available about the microcirculation in the subsynovial connective tissue in patients with CTS. The aims of this study were to use contrast-enhanced ultrasonography (US) to evaluate blood flow in the subsynovial connective tissue proximal to the carpal tunnel in patients with CTS before and after carpal tunnel release.

METHODS

The study included 15 volunteers and 12 patients with CTS. The blood flow in the subsynovial connective tissue and the median nerve was evaluated preoperatively and at 1, 2, and 3 months postoperatively using contrast-enhanced US.

RESULTS

The blood flow in the subsynovial connective tissue was higher in the patients with CTS than in the volunteers. In the patients with CTS, there was a significant correlation between the blood flow in the subsynovial connective tissue and the median nerve (P = .01). The blood flow in both the subsynovial connective tissue and the median nerve increased markedly after carpal tunnel release.

CONCLUSIONS

Our results suggest that increased blood flow in the subsynovial connective tissue may play a role in the alteration of the microcirculation within the median nerve related to the pathophysiologic mechanisms of CTS. The increase in the blood flow in the subsynovial connective tissue during the early postoperative period may contribute to the changes in intraneural circulation, and these changes may lead to neural recovery.

Ultrasonographic demonstration of intraneural neovascularization after penetrating nerve injury

INTRODUCTION

Hypervascularization of nerves has been shown to be a pathological sign in some peripheral nerve disorders, but has not been investigated in nerve trauma.

METHODS

An observational cohort study was performed of the intraneural blood flow of 30 patients (34 nerves) with penetrating nerve injuries, before or after nerve reconstruction. All patients underwent electrophysiological assessment, and B-mode and color Doppler ultrasonography.

RESULTS

Intraneural hypervascularization proximal to the site of injury was found in all nerves, which was typically marked and had a longitudinal extension of several centimeters. In 6 nerves, some blood flow was also present within the injury site or immediately distal to the injury. No correlation was found between the degree of vascularization and age, size of the scar / neuroma, or degree of reinnervation.

DISCUSSION

Neovascularization of nerves proximal to injury sites appears to be an essential element of nerve regeneration after penetrating nerve injuries. Muscle Nerve 57: 994-999, 2018.

Effects of hemodialysis on intraneural blood flow in end-stage kidney disease

INTRODUCTION

We quantified intraneural blood flow (INBF) in 18 patients with end-stage kidney disease (ESKD) and examined its relationship with nerve size, neuropathy severity, and nerve excitability parameters.

METHODS

Sonographic measurements of the median nerve were performed at the same site before and after hemodialysis. INBF was quantified by analyzing power Doppler sonograms to obtain the vessel score (VSc) and maximum perfusion intensity (MPI). Corresponding median motor nerve excitability studies were performed. Neuropathy severity was assessed using Total Neuropathy Score.

RESULTS

A total of 39% of ESKD patients had detectable INBF compared with none in the control group (P < 0.0001). Patients with detectable INBF had larger nerves and more severe neuropathy (P < 0.01). INBF parameters were significantly reduced after a session of dialysis (VSc: P < 0.01; MPI: P < 0.01). A significant relationship was found between interdialytic change in INBF and changes in nerve excitability.

CONCLUSIONS

Increased INBF is a potential marker for neuropathy severity in ESKD patients. Muscle Nerve 57: 287-293, 2018.

Value of superb microvascular imaging ultrasonography in the diagnosis of carpal tunnel syndrome: Compared with color Doppler and power Doppler

The aim of this study was to compare the value of superb microvascular imaging (SMI) in carpal tunnel syndrome (CTS) with that of color Doppler ultrasonography (CDUS) and power Doppler ultrasonography (PDUS).Fifty patients with symptomatic CTS and 25 healthy volunteers were enrolled. The cross-sectional area (CSA), CDUS score, PDUS score, and SMI score of the median nerve (MN) at the carpal tunnel were recorded. The value of different ultrasonography (US) diagnostic strategies was calculated.The blood flow display ratio in the MN of the healthy volunteers had no statistical difference between CDUS, PDUS, and SMI (20%, 32%, and 48%, respectively, P >.05). The blood flow display ratio for SMI in patients was significantly higher than that of CDUS and PDUS (90%, 52%, and 60%, respectively, P <.005). The accuracy of SMI score ≥2 (79%) was much higher than that of CDUS and PDUS (61% and 63%, respectively, P <.05). Comprehensive consideration of SMI and CSA, CSA≥10.5 mm, and/or SMI score ≥2 has the highest accuracy (83%), significantly higher than that of CSA combination with CDUS or PDUS (68% and 69%, respectively, P <.05).SMI is more sensitive to display the blood flow in the MN with CTS than CDUS and PDUS. It might significantly improve the diagnosis value for CTS.

Effects of Wrist Posture and Fingertip Force on Median Nerve Blood Flow Velocity

Purpose. The purpose of this study was to assess nerve hypervascularization using high resolution ultrasonography to determine the effects of wrist posture and fingertip force on median nerve blood flow at the wrist in healthy participants and those experiencing carpal tunnel syndrome (CTS) symptoms. Methods. The median nerves of nine healthy participants and nine participants experiencing symptoms of CTS were evaluated using optimized ultrasonography in five wrist postures with and without a middle digit fingertip press (0, 6 N). Results. Both wrist posture and fingertip force had significant main effects on mean peak blood flow velocity. Blood flow velocity with a neutral wrist (2.87 cm/s) was significantly lower than flexed 30° (3.37 cm/s), flexed 15° (3.27 cm/s), and extended 30° (3.29 cm/s). Similarly, median nerve blood flow velocity was lower without force (2.81 cm/s) than with force (3.56 cm/s). A significant difference was not found between groups. Discussion. Vascular changes associated with CTS may be acutely induced by nonneutral wrist postures and fingertip force. This study represents an early evaluation of intraneural blood flow as a measure of nerve hypervascularization in response to occupational risk factors and advances our understanding of the vascular phenomena associated with peripheral nerve compression.

Diagnosing carpal tunnel syndrome with Doppler ultrasonography: a comparison of ultrasonographic measurements and electrophysiological severity

INTRODUCTION

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy. Diagnosis is based on clinical history, physical examination, and electrophysiological studies. Imaging techniques are performed for difficult-to-diagnose cases because they provide information about the morphology of the median nerve. More recently, it has been shown that Doppler ultrasonography can detect increased intraneural blood flow in CTS. The aim of our study is to evaluate the relationship between the severity of CTS, hypervascularization, and cross-sectional area (CSA) to determine the diagnostic value of Doppler ultrasonography.

PATIENTS AND METHODS

The study group comprised 125 wrists of 75 patients who had been diagnosed with CTS, both clinically and electrophysiologically. The control group comprised 100 wrists of 50 healthy volunteers. Wrists were classified into five stages of CTS severity based on electrophysiologic studies. A radiologist examined the wrists blindly with grayscale images and Doppler ultrasonography to assess CSA and hypervascularization.

RESULTS

A total of 121 wrists were included. There were 28 wrists with minimal CTS severity stage, 36 with mild, 36 with moderate, and 21 with severe. The sensitivity and specificity of CSA and hypervascularization in detecting CTS was 90.9, 94.0, 93.4, and 90.0%, respectively. There was a significant correlation between CTS severity and hypervascularization (p < 0.005) for all stages.

CONCLUSION

Our study shows that Doppler ultrasonography results strongly correlate with CTS severity. Hence, this is a useful method for diagnosing CTS and estimating its severity.

Utility of maximum perfusion intensity as an ultrasonographic marker of intraneural blood flow

We quantified intraneural blood flow (INBF) using perfusion measurement software (PixelFlux), and compared it with the qualitative method of counting blood vessels (vessel score) in a cohort of carpal tunnel syndrome (CTS) patients.

METHODS

Forty-seven patients (67 wrists) with a clinical and electrophysiological diagnosis of CTS, and 20 healthy controls (40 wrists) were enrolled. Median nerve ultrasound (US) was performed at the carpal tunnel inlet to measure the cross-sectional area (CSA) and vessel score. Power Doppler sonograms from nerves with detectable INBF were processed with PixelFlux to obtain the maximum perfusion intensity (MPI).

RESULTS

Forty-nine percent of CTS patients had detectable INBF compared with none in the control group (P < 0.0001). MPI correlated significantly with vessel score (r = 0.945, P < 0.0001), CSA (r = 0.613, P < 0.0001), and electrophysiological severity (r = 0.440, P < 0.0001). MPI had higher intra- or interobserver reliability compared with vessel score (0.95 vs. 0.47).

CONCLUSION

MPI is a better method for quantification of INBF. Muscle Nerve, 2016 Muscle Nerve 55: 77-83, 2017.

Detection of Intraneural Median Nerve Microvascularity Using Contrast-Enhanced Sonography: A Pilot Study

OBJECTIVES

Demonstrating vascularity within the human median nerve may be difficult using power Doppler sonography. To this end, a pilot study documenting contrast-enhanced vascularity of the median nerve was conducted.

METHODS

Patients undergoing contrast-enhanced transthoracic echocardiography were recruited for this study (n = 24). During echocardiography, a simultaneous contrast-enhanced sonographic examination of the median nerve was conducted. The study and study protocol were built from preclinical evidence. Image analysis was based on the power Doppler pixel intensity within a defined region of interest to obtain quantitative data representing the average pixel intensity, maximum pixel intensity, and power Doppler pixel dot count. Semiquantitative data representing the power Doppler dot count grading were also obtained.

RESULTS

Spearman correlations between analytical methods showed strong positive, statistically significant (P< .05) correlations between the average pixel intensity and maximum pixel intensity and between the power Doppler dot count and dot count grading. Statistically significant increases in the average pixel intensity and power Doppler dot count were seen at all but 1 time point throughout the contrast-enhanced sonographic examination when compared to precontrast administration. Statistically significant increases in the maximum pixel intensity were seen at all but 4 time points.

CONCLUSIONS

These pilot results represent early evidence that contrast-enhanced sonography can be used to image median nerve vascularity. In this convenience sample, median nerve contrast-enhanced sonographic data collection was feasible, safe, and consistent.

Doppler sonography for ulnar neuropathy at the elbow

INTRODUCTION

The aim of this study was to determine the value of Doppler sonography for evaluation of ulnar neuropathy at the elbow (UNE).

METHODS

A total of 102 patients with a clinical suspicion of UNE and 50 healthy controls were examined by Doppler and gray-scale sonography.

RESULTS

Intraneural vascularization was found in 31 (46.3%) of 67 patients with confirmed UNE and in 3 (6.0%) of 50 healthy controls. Combining gray-scale sonography measurement of nerve size and the presence of intraneural vascularization increased sensitivity by 3%, but decreased the specificity. Patients with intraneural vascularization had more severe disease than those without intraneural vascularization (P < 0.05). The variables obtained by Doppler sonography were associated with the severity of UNE (P < 0.05).

CONCLUSIONS

Doppler sonography is not helpful for diagnosing UNE but can be used to assess the severity of UNE. Muscle Nerve 54: 258-263, 2016.

Electrosonodiagnosis in Carpal Tunnel Syndrome: A Proposed Diagnostic Algorithm Based on an Analytic Literature Review

BACKGROUND

Suspected carpal tunnel syndrome (CTS) remains the most common clinical scenario prompting referral for electrodiagnostic (EDx) studies to identify objective correlates of reported subjective symptoms and clinical examination findings. Despite much debate and a rapidly expanding literature, identification of an optimal algorithm for diagnosing focal median mononeuropathy at the wrist (FMMW) associated with CTS signs and symptoms remains elusive. The introduction and rapid dissemination of peripheral nerve ultrasound imaging (PN-USI) of the median nerve has raised new questions regarding the relative value of structural information from PN-USI versus physiological information from EDx in the diagnosis of FMMW, as well as the significance of various clinical signs and symptoms suggestive of CTS. The means by which PN-USI and EDx may be optimally deployed and integrated in the process of diagnosing FMMW remains to be clearly delineated.

OBJECTIVE

To complete an analytical literature review to guide the formulation of a clinical diagnostic algorithm (CDA) integrating the use of PN-USI and EDx for the optimal detection of FMMW in the context of making a clinical diagnosis of CTS.

DATA SOURCES

A structured literature review was performed on the MEDLINE medical literature database accessed through PubMed.

ANALYSIS

Papers with particular relevance and connection to the goal of formulating the CDA were selected from the identified studies. Studies specifically examining the correlations between systematically documented clinical symptomatology, EDx findings, and PN-USI findings were reviewed for consistent outcomes that could be incorporated into a CDA to guide the integration of these two complementary technologies in the diagnostic process.

LIMITATIONS

The formulation of the algorithm was limited to measures with established validity that can be readily obtained by means of widely accepted protocols using standard EDx and ultrasound equipment. The formulated algorithm assumes a consistent association between pathophysiology and anatomical deformation of the median nerve, which may not occur in certain situations. It may also not be as accurately applied to patients with CTS with significant comorbid neuromuscular conditions.

CONCLUSIONS

An algorithm has been developed and presented, and illustrated as a flow chart, based on findings reported in the relevant reviewed literature in which PN-USI is proposed as a painless and rapidly performed screening test for FMMW to be completed before subjecting a patient to a systematic EDx testing process.

Peripheral nerve imaging

Disorders of peripheral nerve have been traditionally diagnosed and monitored using clinical and electrodiagnostic approaches. The last two decades have seen rapid development of both magnetic resonance imaging (MRI) and ultrasound imaging of peripheral nerve, such that these imaging modalities are increasingly invaluable to the diagnosis of patients with peripheral nerve disorders. Peripheral nerve imaging provides information which is supplementary to clinical and electrodiagnostic diagnosis. Both MRI and ultrasound have particular benefits in specific clinical circumstances and can be considered as complementary techniques. These technologic developments in peripheral nerve imaging will usher in an era of multimodality assessment of peripheral nerve disorders, with clinical evaluations supported by anatomic information from imaging, and functional information from electrodiagnostic studies. Such a multimodality approach will improve the accuracy and efficiency of patient care.

Entrapment and traumatic neuropathies of the elbow and hand: An imaging approach

Ultrasound and magnetic resonance imaging currently offer a detailed analysis of the peripheral nerves. Compressive and traumatic nerve injuries are the two main indications for imaging investigation of nerves with several publications describing the indications, technique and diagnostic capabilities of imaging signs. Investigation of entrapment neuropathies has three main goals, which are to confirm neuronal distress, search for the cause of nerve compression and exclude a differential diagnosis on the entire nerve. For traumatic nerve injuries, imaging, predominantly ultrasound, occasionally provides essential information for management including the type of nerve lesion, its exact site and local extension.

Ultrasound in the diagnosis of peripheral neuropathy: structure meets function in the neuromuscular clinic

Peripheral nerve ultrasound (US) has emerged as a promising technique for the diagnosis of peripheral nerve disorders. While most experience with US has been reported in the context of nerve entrapment syndromes, the role of US in the diagnosis of peripheral neuropathy (PN) has recently been explored. Distinctive US findings have been reported in patients with hereditary, immune-mediated, infectious and axonal PN; US may add complementary information to neurophysiological studies in the diagnostic work-up of PN. This review describes the characteristic US findings in PN reported to date and a classification of abnormal nerve US patterns in PN is proposed. Closer scrutiny of nerve abnormalities beyond assessment of nerve calibre may allow for more accurate diagnostic classification of PN, as well as contribute to the understanding of the intersection of structure and function in PN.

High-frequency ultrasound in carpal tunnel syndrome: assessment of patient eligibility for surgical treatment

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy and a frequent cause of sick leaves because of work-related hand overload. That is why an early diagnosis and adequate treatment (conservative or surgical) are essential for optimal patient management.

Doppler sonography for the diagnosis of carpal tunnel syndrome: a critical review

INTRODUCTION

Doppler sonography may detect increased intraneural blood flow of the median nerve in carpal tunnel syndrome (CTS). The purpose of this review is to critically evaluate the literature about the diagnostic value of increased intraneural flow detected by sonography in CTS Methods: Systematic review of studies published between 1985 and 2013.

RESULTS

The 7 studies we found had considerable differences in study design and had methodological shortcomings. Doppler sonography had a median sensitivity of 72% (range, 41-95%) and a median specificity of 88% (range, 71-100%). Most studies could not compare the diagnostic value of sonography to that of electrophysiological studies, because the latter were often used as a reference test.

CONCLUSIONS

Increased intraneural flow detected by Doppler sonography may be a promising diagnostic test for CTS, but further studies are needed before it can be implemented in clinical practice.

A comparison of ultrasonographic and electrophysiologic 'inching' in ulnar neuropathy at the elbow

OBJECTIVE

The present study aimed to clarify the relationship between structural ulnar nerve changes and electrophysiological nerve dysfunction in patients with ulnar neuropathy at the elbow (UNE).

METHODS

High-resolution ultrasonography of the ulnar nerve was performed on 17 limbs with clinically and electrophysiologically confirmed UNE, and 52 control subjects at four standardised sites proximal and distal to the medial epicondyle (P2, P1, D1, D2), corresponding to segments of ulnar short-segment nerve conduction studies ("inching studies").

RESULTS

Ulnar nerve cross-sectional area (CSA) and hypoechoic fraction were significantly increased in patients with UNE immediately distal (D1) and proximal (P1) to the medial epicondyle (p<0.01). In patients with UNE, hypoechoic fraction was similar in asymptomatic and symptomatic limbs. Motor nerve conduction velocity across the elbow correlated with CSAmax and the maximum hypoechoic fraction (R=0.6, p<0.05). CSA and hypoechoic fraction of individual segments did not correlate with corresponding latencies on inching studies, but latencies across the D1 segment correlated with CSA at P1 (R=0.80, p<0.0001) and D2 (R=0.65, p<0.01).

CONCLUSIONS

Sonographic abnormalities in UNE may not be maximal at the site of electrophysiological nerve dysfunction.

SIGNIFICANCE

Sonographic abnormalities may reflect secondary pathophysiological changes in segments adjacent to regions of nerve compression.

Reliability of peripheral intraneural microhemodynamics evaluation by using contrast-enhanced ultrasonography

PURPOSE

The purpose of the study was to validate the reliability of quantitative intraneural enhancement patterns by using contrast-enhanced ultrasonography (CEUS).

METHODS

Nine asymptomatic wrists underwent a total of three CEUS examinations each conducted at 1-month intervals. The CEUS enhancement pattern of median nerves was quantitatively evaluated. The area under the time-intensity curve was calculated by placing the regions of interest at the proximal, center, and distal regions of the median nerve. An intra-class correlation coefficient for intra-observer, inter-observer, and inter-examination reproducibility was calculated.

RESULTS

The intra- and inter-observer reproducibility was almost perfect. Inter-examination reproducibility of the proximal, center, and distal regions was 0.891, 0.614, and 0.535, respectively. In this study, we found that the reproducibility of the distal and center regions of the median nerve in the carpal tunnel was lower than that of the proximal region.

CONCLUSION

High intra-observer, inter-observer, and inter-examination reproducibility of CEUS was obtained in the evaluation of the intraneural enhancement pattern when the region of interest was placed in the proximal region of the median nerve.

Does measuring the median nerve at the carpal tunnel outlet improve ultrasound CTS diagnosis?

INTRODUCTION

Nerve conduction is often regarded as more sensitive than ultrasonography (US) for diagnosing carpal tunnel syndrome (CTS). The diagnostic value of US derives from median nerve enlargement occurring at both ends of the carpal tunnel resulting in a dumbbell-like swelling from carpal tunnel pressure. An important reason for the inferior sensitivity of US may be because measurements are restricted to the carpal tunnel inlet. We investigate the value of including median nerve enlargement at the carpal tunnel outlet for diagnosing CTS.

METHODS

Retrospective cohort study of nerve conduction verified CTS, determining sensitivity, specificity, and positive and negative predictive values of carpal tunnel inlet and outlet median nerve cross sectional area as determined by US for the diagnosis of CTS. Nerve conduction graded CTS severity.

RESULTS

127 hands from 77 patients with CTS and 35 control healthy hands were assessed. US sensitivity for diagnosing CTS increased from 65% to 84% by including outlet enlargement of the median nerve. Specificity changed from 94% to 86%, positive predictive value from 98% to 96% and the negative predictive value from 43% to 60%. 25 hands out of the 127 from CTS patients showed enlargement restricted to the outlet and mainly occurred in moderate CTS.

CONCLUSION

In our population, the use of carpal tunnel outlet median nerve enlargement in addition to inlet median nerve size increases sensitivity for diagnosing CTS by 19%.

Longitudinal Analysis of Median Nerve Perfusion Using Spectral Doppler in a Working Animal Model

Carpal tunnel syndrome (CTS) is a form of median mononeuropathy (MMN) of the wrist that has become the most common nerve entrapment syndrome of the upper limbs. During the acute phase of CTS, the median nerve becomes hyperemic and enlarged as it begins to be compressed by the transverse carpal ligament; however, continual compression ultimately leads to median nerve ischemia. The objective of this study was to longitudinally quantify the amount of perfusion of the median nerve using spectral Doppler in a working animal model, as the cohort prospectively increased their risk of MMN through a repetitive pinching task. The results of the study provided low-level evidence that the use of spectral Doppler to accurately detect longitudinal changes in vascularity within the median nerve may be diagnostically inadequate. As the subjects in the study moved through the working and nonworking stages of study, spectral Doppler alone proved to lack the level of sensitivity needed to detect physiologic changes within the nerve. This outcome, although inconclusive when it comes to detecting changes in median nerve vascularity, does suggest the need for this method to be analyzed in conjunction with other sonographic features and provocative testing.

Use of contrast-enhanced sonography to investigate intraneural vascularity in a cohort of Macaca fascicularis with suspected median mononeuropathy

OBJECTIVES

The purpose of this study was to provide clinical evidence of the use of contrast-enhanced sonography in detecting and quantifying changes in intraneural vascularity due to median mononeuropathy.

METHODS

Five Macaca fascicularis monkeys were exposed to 20 weeks of repetitive work to increase their risk of developing median mononeuropathy. Contrast-enhanced sonograms were obtained in 30-second increments for 7 minutes while a contrast agent was being delivered. Data were collected immediately at the conclusion of the 20-week work exposure and then again during a recovery phase approximately 3 months after the completion of work. Quantitative analysis and trend graphs were used to analyze median nerve perfusion intensity. This study also compared the use of both manual counting of pixels and semiautomatic measurement using specialized software.

RESULTS

Based on the average data, maximum intensity values were identified as the best indicators of nerve hyperemia. Paired t tests demonstrated significantly higher maximum intensities in the working stage for 4 of the 5 subjects (P < .01).

CONCLUSIONS

This study provides preliminary evidence that (1) in a controlled exposure model, a change in intraneural vascularity of the median nerve between working and recovery can be observed; (2) this vascular change can be measured using an objective technique that quantifies the intensity of vascularity; and (3) contrast-enhanced sonography may improve the ability to reliably capture and measure low-flow microvascularity.

Establishing an Imaging Protocol for Detection of Vascularity within the Median Nerve Using Contrast-Enhanced Ultrasound

This preclinical study was conducted to develop discrete sonographic instrumentation settings and also safe contrast dosing that would consistently demonstrate perineural vascularity along the median nerve. This set of imaging studies was conducted with a convenience cohort of young adult female monkeys (Macaca fascicularis). Sonographic equipment settings and dosing were refined throughout the imaging series to ensure consistent contrast-enhanced ultrasound imaging. A mechanical index of 0.13 was consistently used for imaging. Perineural vessels were imaged with a suspension solution of 0.04 mL Definity/0.96 mL saline introduced over 5 minutes for a total dose of 0.8 mL of contrast solution. Blinded studies of high and low dose contrast, along with saline injections, were correctly identified by two experienced sonographers. This preclinical study established adequate equipment settings and dosing that allowed for a valid demonstration of vascularity surrounding the median nerve.

Ultrasonography of peripheral nerves

Over the last decade, neuromuscular ultrasonography has emerged as a useful tool for the diagnosis of peripheral nerve disorders. This article reviews sonographic findings of normal nerves, including key quantitative ultrasound measurements that are helpful in the evaluation of focal and possibly generalized peripheral neuropathies. It also discusses several recent articles outlining the evidence base for the use of this technology, as well as new findings in compressive, traumatic, and generalized neuropathies. Ultrasonography is well suited for use in electrodiagnostic laboratories, where physicians, experienced in both the clinical evaluation of patients and the application of hands-on technology, can integrate findings from the patient's history, physical examination, electrophysiological studies, and imaging for diagnosis and management.

Imaging of the peripheral nervous system

This chapter summarizes progress in the evaluation of peripheral nerve (PN) lesions and disorders by imaging techniques encompassing magnetic resonance imaging (MRI) and nerve ultrasound (US). Due to the radiation exposure and limited sensitivity in soft tissue contrast, computed-tomography (CT) plays no significant role in the diagnostic work-up of PN disorders. MRI and US are complementary techniques for the evaluation of peripheral nerves, each having particular advantages and disadvantages. Nerve injury induces intrinsic MRI signal alterations on T2-weighted sequences in degenerating or demyelinating nerve segments as well as in corresponding muscle groups exhibiting denervation which can be exploited diagnostically. Nerve US is based on changes in the nerve echotexture due to tumor formation or focal enlargement caused by entrapment or inflammation. Both MRI and US provide morphological information on the precise site and extent of nerve injury. While US has the advantage of easy accessibility, providing images with superior spatial resolution at low cost, MRI shows better soft tissue contrast and better image quality for deep-lying nerve structures since imaging is not hindered by bone. Recent advances have remarkably increased spatial resolution of both MRI and US making imaging indispensible for the elucidation of causes of nerve compression, peripheral nerve tumors, and focal inflammatory conditions. Both MRI and US further guide neurosurgical exploration and can simplify treatment. Importantly, imaging can reveal treatable conditions even in the absence of gross electrophysiological alterations, illustrating its increasing role in clinical practice. In experimental settings, novel molecular and cellular MRI contrast agents allow in-vivo assessment of nerve regeneration as well as monitoring of neuroinflammation. Depending on further clinical development, contrast-enhanced MRI has the potential to follow cellular responses over time in vivo and to overcome the current limitations of histological assessment of nerve afflictions. Further advances in contrast-enhanced US has the potential for developing into a tool for the assessment of nerve blood perfusion, paving the way for better assessments of ischemic neuropathies.

Provocation tests in doppler ultrasonography for carpal tunnel syndrome

INTRODUCTION

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.