Dynamics of progressive degeneration of major spinal pathways following spinal cord injury: A longitudinal study

Neurodegeneration and Demyelination in the Multiple Sclerosis Spinal Cord: Clinical, Pathological, and 7T MRI Perspectives

BACKGROUND AND OBJECTIVES

Key findings in people with multiple sclerosis (MS) with progressive motor disability are spinal cord (SC) atrophy signifying irreversible axonal loss and SC demyelinated lesions. This study aimed to identify neurodegenerative changes and assess the clinical impact and pathologic characteristics of SC lesions.

METHODS

A cross-sectional study was performed using postmortem cervical cord segments from the Cleveland Clinic MS Rapid Autopsy Program. Inclusion included proximity to our center, absence of transmissible infections, and lack of prolonged hypoxia. In situ MRIs were performed before tissue removal and fixation followed by 7T MRI and immunohistochemistry. Quantitative T2* relaxation times were correlated with myelin, axons, and activated microglia/macrophages (major histocompatibility complex II [MHCII]) using Tukey comparison of means and a linear mixed-effects model; T2* was correlated with clinical disease characteristics using Wilcoxon rank sum.

RESULTS

The study included 40 MS cases (median age 58, female 55%) and 9 controls (median age 69, female 89%). A T2* threshold reliably discriminated demyelination (accuracy 89.7%, sensitivity 95.5%, and specificity 87.0%). Myelin content (95% CI -0.82 to -0.58, estimate -0.70) was the only significant predictor of T2*. T2* hyperintensities within the segments ranged from 0% to 100% (median 33.6, interquartile range 12.9-64.3) with only 57.1% demyelinated. T2*-hyperintense/myelinated regions had increased T2* relaxation time (19.2 ms, 95% CI 9.97-28.4), reduced myelin content (-8.3%, 95% CI -12.1 to -4.4), increased MHCII (3.6%, 95% CI 0.45-6.7), reduced axonal counts (-349.8, 95% CI -565.4 to -134.1), and increased axonal area (2.0 µm2, 95% CI 1.0-3.1) compared with normal-appearing MRI regions. These regions occurred adjacent to T2*-hyperintense/demyelinated lesions (periplaque) or along tracts (tract-based). 7T postmortem T2* hyperintensities were subtle on clinical 1.5T axial T2, and only 43% were detected sagittally. T2*-hyperintense/demyelinated lesions correlated with Expanded Disability Status Scale (EDSS) (rho = 0.61, p < 0.0001) and upper cervical cord area (rho = -0.64, p < 0.0001) while T2*-hyperintense/myelinated regions did not.

DISCUSSION

Thresholding 7T T2* postmortem MRI can effectively discriminate demyelinated lesions which correlate with clinical disability and cord atrophy. T2*-hyperintense/myelinated regions exhibit myelin and axonal pathology in periplaque or tract-based distributions suggestive of neurodegeneration. Limitations include sampling of 2-cm of SC across participants making conclusions about proximal and distal pathology difficult.

Therapeutic strategies that modulate the acute phase of secondary spinal cord injury scarring and inflammation and improve injury outcomes

INTRODUCTION

The acute phase of secondary spinal cord injury (SCI) is a crucial therapeutic window to mitigate ongoing damage and promote tissue repair. The present systematic review critically evaluates the efficacy and safety of current management modalities for this phase, identifying gaps in knowledge and providing insights for future research directions.

METHODS

In December 2024, PubMed, Web of Science, Google Scholar, and Embase were accessed with no time constraints. All the clinical studies investigating the pharmacological management of secondary SCI were accessed.

RESULTS

Data from 3017 patients (385 women) were collected. The mean length of the follow-up was 6 ± 3.4 months, and the mean age of the patients was 43.3 ± 10.3 years.

CONCLUSION

Erythropoietin (EPO) improves motor function, reduces impairment in secondary spinal cord injury, modulates antioxidation and neurogenesis, and minimizes apoptosis and inflammation. Although commonly administered, methylprednisolone shows uncertain efficacy. The rho-GTPases inhibitor VX-210 and levetiracetam did not demonstrate effectiveness in treatment. Monosialotetrahexosylganglioside Sodium Salt (GM-1) and riluzole are associated with favorable neurological outcomes. Granulocyte Colony-Stimulating Factor (G-CSF) and Hepatocyte Growth Factor (HGF) offer improved motor scores with fewer side effects.

Spinal Cord Blood Perfusion Deficit is Associated with Clinical Impairment after Spinal Cord Injury

Spinal cord injury (SCI) results in intramedullary microvasculature disruption and blood perfusion deficit at and remote from the injury site. However, the relationship between remote vascular impairment and functional recovery remains understudied. We characterized perfusion impairment in vivo, rostral to the injury, using magnetic resonance imaging (MRI), and investigated its association with lesion extent and impairment following SCI. Twenty-one patients with chronic cervical SCI and 39 healthy controls (HC) underwent a high-resolution MRI protocol, including intravoxel incoherent motion (IVIM) and T2*-weighted MRI covering C1-C3 cervical levels, as well as T2-weighted MRI to determine lesion volumes. IVIM matrices (i.e., blood volume fraction, velocity, flow indices, and diffusion) and cord structural characteristics were calculated to assess perfusion changes and cervical cord atrophy, respectively. Patients with SCI additionally underwent a standard clinical examination protocol to assess functional impairment. Correlation analysis was used to investigate associations between IVIM parameters with lesion volume and sensorimotor dysfunction. Cervical cord white and gray matter were atrophied (27.60% and 21.10%, p < 0.0001, respectively) above the cervical cord injury, accompanied by a lower blood volume fraction (-22.05%, p < 0.001) and a higher blood velocity-related index (+38.72%, p < 0.0001) in patients with SCI compared with HC. Crucially, gray matter remote perfusion deficit correlated with larger lesion volumes and clinical impairment. This study shows clinically eloquent perfusion deficit rostral to a SCI, its magnitude driven by injury severity. These findings indicate trauma-induced widespread microvascular alterations beyond the injury site. Perfusion MRI matrices in the spinal cord hold promise as biomarkers for monitoring treatment effects and dynamic changes in microvasculature integrity following SCI.

White matter spinal tracts impairment in patients with degenerative cervical myelopathy evaluated with the magnetization transfer saturation MRI technique

STUDY DESIGN

Prospective case-control study.

OBJECTIVES

We investigated the use of the magnetization transfer saturation (MTsat) technique to assess the structural integrity of the spinal cord tracts in individuals with clinically significant degenerative cervical myelopathy (DCM) and associated disability.

SETTING

Novosibirsk Neurosurgery Centre, Russia.

METHODS

A total of 53 individuals diagnosed with DCM and 41 patients with cervical radiculopathy underwent high-resolution MRI of the cervical spinal cord via the magnetization transfer technique. The MRI data were processed using the Spinal Cord Toolbox (v5.5), with MTsat values determined for each spinal tract and compared between the two groups. Furthermore, associations between MTsat values and the clinical disability rates of patients were investigated.

RESULTS

A significant decrease in the MTsat of the ventral spinocerebellar tract was observed in the DCM group compared to the control group (adjusted p < 0.001). There was a trend towards lower MTsat values in the rubrospinal tract in the DCM group (adjusted p = 0.08). Additionally, a decrease in MTsat values in the lateral funiculi of the spinal cord was found in patients with DCM (adjusted p < 0.01). Furthermore, a trend toward a positive correlation was observed between the JOA score and the MTsat values within the ventral spinocerebellar tract (R = 0.33, adjusted p = 0.051).

CONCLUSIONS

The findings of our study indicate that demyelination in patients with DCM affects mainly the ventral spinocerebellar and rubrospinal tracts, and the extent of changes in the ventral spinocerebellar tract is related to the severity of the condition.

Tensor denoising of quantitative multi-parameter mapping

PURPOSE

Quantitative multi-parameter mapping (MPM) provides maps of physical quantities representing physiologically meaningful tissue characteristics, which allows to investigate microstructure-function relationships reflecting normal or pathologic processes in the brain. However, the achievable spatial resolution and stability of MPM for basic research or clinical applications is severely constrained by SNR limits of the MR acquisition process, resulting in relatively long acquisition times. To increase SNR, we denoise MPM acquisitions using principal component analysis along tensors exploiting the Marchenko-Pastur law (tMPPCA).

METHODS

tMPPCA denoising was applied to three sets of MPM raw data before the quantification of maps of proton density, magnetization transfer saturation, R1, and R2*. The regional SNR gain for high-resolution MPM was investigated as well as reproducibility gains for clinically optimized protocols with moderate and high acceleration factors at different image resolutions.

RESULTS

Substantial noise reduction in raw data was achieved, resulting in reduced noise for quantitative mapping up to sixfold without introducing bias of mean values (below 1%). Scan-rescan fluctuations were reduced up to threefold. Denoising allowed to decrease the voxel volume fourfold at the same scan time or reduce the scan time twofold at same voxel volume without loss of sensitivity.

CONCLUSIONS

tMPPCA denoising can (a) improve of fine spatial and temporal patterns, (b) considerably reduce scan time for clinical applications, or (c) increase resolution to potentially push cutting-edge MPM protocols from the upper to the lower limit of the mesoscopic scale.

Reliability of spinal cord measures based on synthetic T1-weighted MRI derived from multiparametric mapping (MPM)

Short MRI acquisition time, high signal-to-noise ratio, and high reliability are crucial for image quality when scanning healthy volunteers and patients. Cross-sectional cervical cord area (CSA) has been suggested as a marker of neurodegeneration and potential outcome measure in clinical trials and is conventionally measured on T₁-weigthed 3D Magnetization Prepared Rapid Acquisition Gradient-Echo (MPRAGE) images. This study aims to reduce the acquisition time for the comprehensive assessment of the spinal cord, which is typically based on MPRAGE for morphometry and multi-parameter mapping (MPM) for microstructure. The MPRAGE is replaced by a synthetic T₁-w MRI (synT₁-w) estimated from the MPM, in order to measure CSA. SynT₁-w images were reconstructed using the MPRAGE signal equation based on quantitative maps of proton density (PD), longitudinal (R₁) and effective transverse (R₂*) relaxation rates. The reliability of CSA measurements from synT₁-w images was determined within a multi-center test-retest study format and validated against acquired MPRAGE scans by assessing the agreement between both methods. The response to pathological changes was tested by longitudinally measuring spinal cord atrophy following spinal cord injury (SCI) for synT₁-w and MPRAGE using linear mixed effect models. CSA measurements based on the synT₁-w MRI showed high intra-site (Coefficient of variation [CoV]: 1.43% to 2.71%) and inter-site repeatability (CoV: 2.90% to 5.76%), and only a minor deviation of -1.65 mm² compared to MPRAGE. Crucially, by assessing atrophy rates and by comparing SCI patients with healthy controls longitudinally, differences between synT₁-w and MPRAGE were negligible. These results demonstrate that reliable estimates of CSA can be obtained from synT₁-w images, thereby reducing scan time significantly.