Ultrasound in Traumatic Spinal Cord Injury: A Wide-Open Field

Inflammatory response in traumatic brain and spinal cord injury: The role of XCL1-XCR1 axis and T cells

BACKGROUND

Traumatic brain injury (TBI) and spinal cord injury (SCI) are acquired injuries to the central nervous system (CNS) caused by external forces that cause temporary or permanent sensory and motor impairments and the potential for long-term disability or even death. These conditions currently lack effective treatments and impose substantial physical, social, and economic burdens on millions of people and families worldwide. TBI and SCI involve intricate pathological mechanisms, and the inflammatory response contributes significantly to secondary injury in TBI and SCI. It plays a crucial role in prolonging the post-CNS trauma period and becomes a focal point for a potential therapeutic intervention. Previous research on the inflammatory response has traditionally concentrated on glial cells, such as astrocytes and microglia. However, increasing evidence highlights the crucial involvement of lymphocytes in the inflammatory response to CNS injury, particularly CD8+ T cells and NK cells, along with their downstream XCL1-XCR1 axis.

OBJECTIVE

This review aims to provide an overview of the role of the XCL1-XCR1 axis and the T-cell response in inflammation caused by TBI and SCI and identify potential targets for therapy.

METHODS

We conducted a comprehensive search of PubMed and Web of Science using relevant keywords related to the XCL1-XCR1 axis, T-cell response, TBI, and SCI.

RESULTS

This study examines the upstream and downstream pathways involved in inflammation caused by TBI and SCI, including interleukin-15 (IL-15), interleukin-12 (IL-12), CD8+ T cells, CD4+ T cells, NK cells, XCL1, XCR1+ dendritic cells, interferon-gamma (IFN-γ), helper T0 cells (Th0 cells), helper T1 cells (Th1 cells), and helper T17 cells (Th17 cells). We describe their proinflammatory effect in TBI and SCI.

CONCLUSIONS

The findings suggest that the XCL1-XCR1 axis and the T-cell response have great potential for preclinical investigations and treatments for TBI and SCI.

Spinal Cord Injury: Emerging Technologies

The mainstay of treatment for spinal cord injury includes decompressive laminectomy and elevation of mean arterial pressure. However, outcomes often remain poor. Extensive research and ongoing clinical trials seek to design new treatment options for spinal cord injury, including stem cell therapy, scaffolds, brain-spine interfaces, exoskeletons, epidural electrical stimulation, ultrasound, and cerebrospinal fluid drainage. Some of these treatments are targeted at the initial acute window of injury, during which secondary damage occurs; others are designed to help patients living with chronic injuries.

Spinal cord injury: molecular mechanisms and therapeutic interventions

Spinal cord injury (SCI) remains a severe condition with an extremely high disability rate. The challenges of SCI repair include its complex pathological mechanisms and the difficulties of neural regeneration in the central nervous system. In the past few decades, researchers have attempted to completely elucidate the pathological mechanism of SCI and identify effective strategies to promote axon regeneration and neural circuit remodeling, but the results have not been ideal. Recently, new pathological mechanisms of SCI, especially the interactions between immune and neural cell responses, have been revealed by single-cell sequencing and spatial transcriptome analysis. With the development of bioactive materials and stem cells, more attention has been focused on forming intermediate neural networks to promote neural regeneration and neural circuit reconstruction than on promoting axonal regeneration in the corticospinal tract. Furthermore, technologies to control physical parameters such as electricity, magnetism and ultrasound have been constantly innovated and applied in neural cell fate regulation. Among these advanced novel strategies and technologies, stem cell therapy, biomaterial transplantation, and electromagnetic stimulation have entered into the stage of clinical trials, and some of them have already been applied in clinical treatment. In this review, we outline the overall epidemiology and pathophysiology of SCI, expound on the latest research progress related to neural regeneration and circuit reconstruction in detail, and propose future directions for SCI repair and clinical applications.

Technical Aspects of Intra-Operative Ultrasound for Spinal Cord Injury and Myelopathy: A Practical Review

OBJECTIVES

To compile intra-operative techniques, established imaging parameters, available equipment and software, and clinical applications of intraoperative ultrasound imaging (IOUSI) for spinal cord injury (SCI) and myelopathy.

METHODS

PubMed and Google Scholar were searched for relevant articles. The articles were reviewed and selected by 2 independent researchers. After article selection, data were extracted and summarized into research domains. PRISMA systematic review process was followed.

RESULTS

Of the 2477 articles screened, 16 articles met the inclusion criteria. In patients with SCI and myelopathy, common quantitative measurements obtained using IOUSI were noted: 1) ultrasound elastography, 2) midsagittal anteroposterior diameter, 3) transverse, 4) transverse diameter, 5) maximum spinal cord compression, and 6) compression ratioTo ensure adequate decompression and to look for residual compression, the lateral and the craniocaudal margins of the laminectomy site were inspected in both axial and sagittal planes. In instances where quantitative assessment was not possible, cord decompression and degree of residual compression were gauged by inspecting the interface between the ventral border of the spinal cord and any potentially compressive elements, and by searching for symmetric and rhythmic cerebrospinal fluid pulsations. Use of contrast-enhanced ultrasoundand molecular imaging are additional advances in objective assessments for SCI and myelopathy.

CONCLUSIONS

This review outlines the potential of IOUSI in patients presenting with SCI and myelopathy. Moreover, by identifying potential for inter-operator variability in certain subjective measurements, we illustrate the need for further research to quantify and standardize those assessments.

Quantifying Intraparenchymal Hemorrhage after Traumatic Spinal Cord Injury: A Review of Methodology

Intraparenchymal hemorrhage (IPH) after a traumatic injury has been associated with poor neurological outcomes. Although IPH may result from the initial mechanical trauma, the blood and its breakdown products have potentially deleterious effects. Further, the degree of IPH has been correlated with injury severity and the extent of subsequent recovery. Therefore, accurate evaluation and quantification of IPH following traumatic spinal cord injury (SCI) is important to define treatments' effects on IPH progression and secondary neuronal injury. Imaging modalities, such as magnetic resonance imaging (MRI) and ultrasound (US), have been explored by researchers for the detection and quantification of IPH following SCI. Both quantitative and semiquantitative MRI and US measurements have been applied to objectively assess IPH following SCI, but the optimal methods for doing so are not well established. Studies in animal SCI models (rodent and porcine) have explored US and histological techniques in evaluating SCI and have demonstrated the potential to detect and quantify IPH. Newer techniques using machine learning algorithms (such as convolutional neural networks [CNN]) have also been studied to calculate IPH volume and have yielded promising results. Despite long-standing recognition of the potential pathological significance of IPH within the spinal cord, quantifying IPH with MRI or US is a relatively new area of research. Further studies are warranted to investigate their potential use. Here, we review the different and emerging quantitative MRI, US, and histological approaches used to detect and quantify IPH following SCI.

Ultrasound monitoring of microcirculation: An original study from the laboratory bench to the clinic

OBJECTIVE

Monitoring microcirculation and visualizing microvasculature are critical for providing diagnosis to medical professionals and guiding clinical interventions. Ultrasound provides a medium for monitoring and visualization; however, there are challenges due to the complex microscale geometry of the vasculature and difficulties associated with quantifying perfusion. Here, we studied established and state-of-the-art ultrasonic modalities (using six probes) to compare their detection of slow flow in small microvasculature.

METHODS

Five ultrasonic modalities were studied: grayscale, color Doppler, power Doppler, superb microvascular imaging (SMI), and microflow imaging (MFI), using six linear probes across two ultrasound scanners. Image readability was blindly scored by radiologists and quantified for evaluation. Vasculature visualization was investigated both in vitro (resolution and flow characterization) and in vivo (fingertip microvasculature detection).

RESULTS

Superb Microvascular Imaging (SMI) and Micro Flow Imaging (MFI) modalities provided superior images when compared with conventional ultrasound imaging modalities both in vitro and in vivo. The choice of probe played a significant difference in detectability. The slowest flow detected (in the lab) was 0.1885 ml/s and small microvasculature of the fingertip were visualized.

CONCLUSIONS

Our data demonstrated that SMI and MFI used with vascular probes operating at higher frequencies provided resolutions acceptable for microvasculature visualization, paving the path for future development of ultrasound devices for microcirculation monitoring.

Ultrasonic spine surgery for every thoracic disc herniation: a 43-patient case series and technical note demonstrating safety and efficacy using a partial transpedicular thoracic discectomy with ultrasonic aspiration and ultrasound guidance

OBJECTIVE

Thoracic disc herniations (TDHs) are a challenging pathology. A variety of surgical techniques have been used to achieve spinal cord decompression. This series elucidates the versatility, efficacy, and safety of the partial transpedicular approach with the use of intraoperative ultrasound and ultrasonic aspiration for resection of TDHs of various sizes, locations, and consistencies. This technique can be deployed to safely remove all TDHs.

METHODS

A retrospective review was performed of patients who underwent a thoracic discectomy via the partial transpedicular approach between January 2014 and December 2020 by a single surgeon. Variables reviewed included demographics, perioperative imaging, and functional outcome scores.

RESULTS

A total of 43 patients (53.5% female) underwent 54 discectomies. The most common presenting symptoms were myelopathy (86%), motor weakness (72%), and sensory deficit (65%) with a symptom duration of 10.4 ± 11.6 months. A total of 21 (38.9%) discs were fully calcified on imaging and 15 (27.8%) were partially calcified. A total of 36 (66.7%) were giant TDHs (> 40% canal compromise). The average operative time was 197.2 ± 77.1 minutes with an average blood loss of 238.8 ± 250 ml. Six patients required ICU stays. Hospital length of stay was 4.40 ± 3.4 days. Of patients with follow-up MRI, 38 of 40 (95%) disc levels demonstrated < 20% residual disc. Postoperative Frankel scores (> 3 months) were maintained or improved for all patients, with 28 (65.1%) patients having an increase of 1 grade or more on their Frankel score. Six (14%) patients required repeat surgery, 2 of which were due to reherniation, 2 were from adjacent-level herniation, and 2 others were from wound problems. Patients with calcified TDHs had similar improvement in Frankel grade compared to patients without calcified TDH. Additionally, improvement in intraoperative neuromonitoring was associated with a greater improvement in Frankel grade.

CONCLUSIONS

The authors demonstrate a minimally disruptive, posterior approach that uses intraoperative ultrasound and ultrasonic aspiration with excellent outcomes and a complication profile similar to or better than other reported case series. This posterior approach is a valuable complement to the spine surgeon's arsenal for the confident tackling of all TDHs.

Neuroinflammation and Scarring After Spinal Cord Injury: Therapeutic Roles of MSCs on Inflammation and Glial Scar

Transected axons are unable to regenerate after spinal cord injury (SCI). Glial scar is thought to be responsible for this failure. Regulating the formation of glial scar post-SCI may contribute to axonal regrow. Over the past few decades, studies have found that the interaction between immune cells at the damaged site results in a robust and persistent inflammatory response. Current therapy strategies focus primarily on the inhibition of subacute and chronic neuroinflammation after the acute inflammatory response was executed. Growing evidences have documented that mesenchymal stem cells (MSCs) engraftment can be served as a promising cell therapy for SCI. Numerous studies have shown that MSCs transplantation can inhibit the excessive glial scar formation as well as inflammatory response, thereby facilitating the anatomical and functional recovery. Here, we will review the effects of inflammatory response and glial scar formation in spinal cord injury and repair. The role of MSCs in regulating neuroinflammation and glial scar formation after SCI will be reviewed as well.