Simultaneous voxel-wise analysis of brain and spinal cord morphometry and microstructure within the SPM framework.

To validate a simultaneous analysis tool for the brain and cervical cord embedded in the statistical parametric mapping (SPM) framework, we compared trauma-induced macro- and microstructural changes in spinal cord injury (SCI) patients to controls. The findings were compared with results obtained from existing processing tools that assess the brain and spinal cord separately. A probabilistic brain-spinal cord template (BSC) was generated using a generative semi-supervised modelling approach. The template was incorporated into the pre-processing pipeline of voxel-based morphometry and voxel-based quantification analyses in SPM. This approach was validated on T1-weighted scans and multiparameter maps, by assessing trauma-induced changes in SCI patients relative to controls and comparing the findings with the outcome from existing analytical tools. Consistency of the MRI measures was assessed using intraclass correlation coefficients (ICC). The SPM approach using the BSC template revealed trauma-induced changes across the sensorimotor system in the cord and brain in SCI patients. These changes were confirmed with established approaches covering brain or cord, separately. The ICC in the brain was high within regions of interest, such as the sensorimotor cortices, corticospinal tracts and thalamus. The simultaneous voxel-wise analysis of brain and cervical spinal cord was performed in a unique SPM-based framework incorporating pre-processing and statistical analysis in the same environment. Validation based on a SCI cohort demonstrated that the new processing approach based on the brain and cord is comparable to available processing tools, while offering the advantage of performing the analysis simultaneously across the neuraxis.

MR Spectroscopy of the Cervical Spinal Cord in Chronic Spinal Cord Injury.

Purpose To investigate metabolic changes in chronic spinal cord injury (SCI) by applying MR spectroscopy in the cervical spinal cord. Materials and Methods Single-voxel short-echo spectroscopic data in study participants with chronic SCI and healthy control subjects were prospectively acquired in the cervical spinal cord at C2 above the level of injury between March 2016 and January 2017 and were compared between groups. Concentrations of total N-acetylaspartate (tNAA), myo-inositol (mI), total choline-containing compounds (tCho), creatine, and glutamine and glutamate complex were estimated from the acquired spectra. Participants were assessed with a comprehensive clinical evaluation investigating sensory and motor deficits. Correlation analysis was applied to investigate relationships between observed metabolic differences, lesion severity, and clinical outcome. Results There were 18 male study participants with chronic SCI (median age, 51 years; range, 30-68 years) and 11 male healthy control subjects (median age, 45 years; range, 30-67 years). At cervical level C2, tNAA/mI and tCho/mI ratios were lower in participants with SCI (tNAA/mI: -26%, P = .003; tCho/mI: -18%; P = .04) than in healthy control subjects. The magnitude of difference was greater with the severity of cord atrophy (tNAA/mI: R2 = 0.44, P = .003; tCho/mI: R2 = 0.166, P = .09). Smaller tissue bridges at the lesion site correlated with lower ratios of tNAA/mI (R2 = 0.69, P = .006) and tCho/mI (R2 = 0.51, P = .03) at the C2 level. Lower tNAA/mI and tCho/mI ratios were associated with worse sensory and motor outcomes (P < .05). Conclusion Supralesional metabolic alterations are observed in chronic spinal cord injury, likely reflecting neurodegeneration, demyelination, and astrocytic gliosis in the injured cervical cord. Lesion severity and greater clinical impairment are both linked to the biochemical changes in the atrophied cervical cord after spinal cord injury. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Lin in this issue.

Quantitative MRI of rostral spinal cord and brain regions is predictive of functional recovery in acute spinal cord injury.

Objective: To reveal the immediate extent of trauma-induced neurodegenerative changes rostral to the level of lesion and determine the predictive clinical value of quantitative MRI (qMRI) following acute spinal cord injury (SCI). Methods: Twenty-four acute SCI patients and 23 healthy controls underwent a high-resolution T1-weighted protocol. Eighteen of those patients and 20 of controls additionally underwent a multi-parameter mapping (MPM) MRI protocol sensitive to the content of tissue structure, including myelin and iron. Patients were examined clinically at baseline, 2, 6, 12, and 24 months post-SCI. We assessed volume and microstructural changes in the spinal cord and brain using T1-weighted MRI, magnetization transfer (MT), longitudinal relaxation rate (R1), and effective transverse relaxation rate (R2*) maps. Regression analysis determined associations between acute qMRI parameters and recovery. Results: At baseline, cord area and its anterior-posterior width were decreased in patients, whereas MT, R1, and R2* parameters remained unchanged in the cord. Within the cerebellum, volume decrease was paralleled by increases of MT and R2* parameters. Early grey matter changes were observed within the primary motor cortex and limbic system. Importantly, early volume and microstructural changes of the cord and cerebellum predicted functional recovery following injury. Conclusions: Neurodegenerative changes rostral to the level of lesion occur early in SCI, with varying temporal and spatial dynamics. Early qMRI markers of spinal cord and cerebellum are predictive of functional recovery. These neuroimaging biomarkers may supplement clinical assessments and provide insights into the potential of therapeutic interventions to enhance neural plasticity.

Volumetric and shape analysis of the thalamus and striatum in amnestic mild cognitive impairment.

Alterations in brain structures, including progressive neurodegeneration, are a hallmark in patients with Alzheimer's disease (AD). However, pathological mechanisms, such as the accumulation of amyloid and the proliferation of tau, are thought to begin years, even decades, before the initial clinical manifestations of AD. In this study, we compare the brain anatomy of amnestic mild cognitive impairment patients (aMCI, n = 16) to healthy subjects (CS, n = 22) using cortical thickness, subcortical volume, and shape analysis, which we believe to be complimentary to volumetric measures. We were able to replicate "classical" cortical thickness alterations in aMCI in the hippocampus, amygdala, putamen, insula, and inferior temporal regions. Additionally, aMCI showed significant thalamic and striatal shape differences. We observed higher global amyloid deposition in aMCI, a significant correlation between striatal displacement and global amyloid, and an inverse correlation between executive function and right-hemispheric thalamic displacement. In contrast, no volumetric differences were detected in thalamic, striatal, and hippocampal regions. Our results provide new evidence for early subcortical neuroanatomical changes in patients with aMCI, which are linked to cognitive abilities and amyloid deposition. Hence, shape analysis may aid in the identification of structural biomarkers for identifying individuals at highest risk of conversion to AD.