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

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.

Update of Contrast-enhanced Ultrasound in Musculoskeletal Medicine: Clinical Perspectives - A Review

Contrast-enhanced ultrasound (CEUS) uses an intravascular contrast agent to enhance blood flow signals and assess microcirculation in different parts of the human body. Over the past decade, CEUS has become more widely applied in musculoskeletal (MSK) medicine, and the current review aims to systematically summarize current research on the application of CEUS in the MSK field, focusing on 67 articles published between January 2001 and June 2021 in online databases including PubMed, Scopus, and Embase. CEUS has been widely used for the clinical assessment of muscle microcirculation, tendinopathy, fracture nonunions, sports-related injuries, arthritis, peripheral nerves, and tumors, and can serve as an objective and quantitative evaluation tool for prognosis and outcome prediction. Optimal CEUS parameters and diagnostic cut off values for each disease category remain to be confirmed.

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.

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.

Ultrasound-guided platelet-rich plasma injection and multimodality ultrasound examination of peripheral nerve crush injury

Ultrasound-guided platelet-rich plasma (PRP) injection is able to make up for the limitations of applying a single growth factor. The goal of this study was to investigate the effects of serial ultrasound-guided PRP injections of the appropriate concentration on the treatment of sciatic nerve crush injury, and explore the value of multimodality ultrasound techniques in evaluating the prognosis of crushed peripheral nerve. In vitro, optimal concentration of PRP (from 150%, 250%, 450%, and 650%) was screened due for its maximal effect on proliferation and neurotrophic function of Schwann cells (SCs). In vivo, ninety rabbits were equally and randomly divided into normal control, model, PRP-2.5×, PRP-4.5×, and PRP-6.5× groups. The neurological function and electrophysiological recovery evaluation, and the comparison of the multimodality ultrasound evaluation with the histological results of sciatic nerve crush injury were performed to investigate the regenerative effects of PRP at different concentrations on the sciatic nerve crush injury. Our results showed that the PRP with a 4.5-fold concentration of whole blood platelets could significantly stimulate the proliferation and secretion of SCs and nerve repair. The changes in stiffness and blood perfusion were positively correlated with the collagen area percentage and VEGF expression in the injured nerve, respectively. Thus, serial ultrasound-guided PRP injections at an appropriate concentration accelerates the recovery of axonal function. Multimodality ultrasound techniques provide a clinical reference for prognosis by allowing the stiffness and microcirculation perfusion of crush-injured peripheral nerves to be quantitatively evaluated.

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.

Evaluation of the Crushed Sciatic Nerve and Denervated Muscle with Multimodality Ultrasound Techniques: An Animal Study

This study was aimed at evaluating the value of multimodality ultrasound techniques in the detection of crushed sciatic nerve and denervated muscle in rabbits. Fifty healthy male New Zealand white rabbits were randomly divided into five groups (n = 10 in each group): four crushed injury groups at 1, 2, 4 and 8 wk post-sciatic nerve crushed injury, and a control group without crush injury. The crushed sciatic nerve and denervated muscle were measured with conventional ultrasound, shear wave elastography and contrast-enhanced ultrasonography, and the results were compared with the histopathological parameters. The inter- and intra-reader reliability of multimodality ultrasound was assessed with intra-class correlation coefficients. Our results revealed that the sciatic nerve thickened at 2 wk post-crushed injury (p < 0.01), but recovered to almost normal thickness at 8 wk post-injury. Stiffness of the crushed nerve gradually increased (p < 0.01), and intraneural blood volume decreased (area under the curve, peak intensity, time to peak, p < 0.01 each) over time. Histopathological evaluation revealed obvious collagen hyperplasia and poor regenerated microvascular and sparse axonal regeneration and remyelination. Compared with that of the control group, the elastic modulus of the denervated muscle significantly increased (p < 0.05), which may be related to the increased intramuscular collagen (p < 0.01) and decreased muscle fiber cross-sectional area (p < 0.01). There were no significant differences in contrast-enhanced ultrasonography parameters (area under the curve, peak intensity, time to peak) of the denervated muscle between the crush injury groups and the control group (p >0.05). All ultrasound results had excellent inter- and intra-reader consistency (intraclass correlation coefficient >0.80). In conclusion, multimodality ultrasound techniques could provide quantitative information on the morphologic changes, mechanical properties and blood perfusion of crushed nerve and denervated muscle, which may be of great importance in clinical practice.

Multimodal magnetic resonance imaging of peripheral nerves: Establishment and validation of brachial and lumbosacral plexi measurements in 163 healthy subjects

PURPOSE

This study aims to provide normal reference values for quantitative parameters for brachial and lumbosacral plexi on multimodal MRI. In addition, the parameter variations between the left and right sides, the individual nerve groups, genders and age groups were also evaluated.

MATERIALS AND METHODS

Multimodal MRI was evaluated in 163 healthy subjects, who were randomly divided into three groups: brachial plexus, lumbosacral plexus and diffusion tensor imaging groups. Nerve diameters, contrast ratios, T2 nerve-muscle signal ratios (nT2), fractional anisotropy (FA) values and apparent diffusion coefficients (ADC) were measured in both plexi. Parametric tests and Pearson correlation for normally distributed data, and non-parametric tests and Spearman correlation for non-normally distributed data were used.

RESULTS

There were no significant differences in parameters between the left and right sides. The diameters of the C7, L4-S1, sciatic, and femoral nerve roots were larger in men than in women (P < 0.05). The nT2 in the brachial and lumbosacral plexi and the contrast ratio in the lumbosacral plexus were significantly higher in the elderly. The diameter of the S1 nerve root was smaller in the elderly. There were no significant differences between the individual nerve groups in contrast ratios and in brachial plexus nT2. A gradual increase in the nT2 from the top to the bottom was observed in the L4-S1 nerve roots (P < 0.05).

CONCLUSION

This study provides multi-parameter normative data for the brachial and lumbosacral plexi while considering differences between the two sides, the individual nerves, genders, and the ages.