Assessment of lesions on magnetic resonance imaging in multiple sclerosis: practical guidelines.

MRI has improved the diagnostic work-up of multiple sclerosis, but inappropriate image interpretation and application of MRI diagnostic criteria contribute to misdiagnosis. Some diseases, now recognized as conditions distinct from multiple sclerosis, may satisfy the MRI criteria for multiple sclerosis (e.g. neuromyelitis optica spectrum disorders, Susac syndrome), thus making the diagnosis of multiple sclerosis more challenging, especially if biomarker testing (such as serum anti-AQP4 antibodies) is not informative. Improvements in MRI technology contribute and promise to better define the typical features of multiple sclerosis lesions (e.g. juxtacortical and periventricular location, cortical involvement). Greater understanding of some key aspects of multiple sclerosis pathobiology has allowed the identification of characteristics more specific to multiple sclerosis (e.g. central vein sign, subpial demyelination and lesional rims), which are not included in the current multiple sclerosis diagnostic criteria. In this review, we provide the clinicians and researchers with a practical guide to enhance the proper recognition of multiple sclerosis lesions, including a thorough definition and illustration of typical MRI features, as well as a discussion of red flags suggestive of alternative diagnoses. We also discuss the possible place of emerging qualitative features of lesions which may become important in the near future.

Individual Assessment of Brain Tissue Changes in MS and the Effect of Focal Lesions on Short-Term Focal Atrophy Development in MS: A Voxel-Guided Morphometry Study.

We performed voxel-guided morphometry (VGM) investigating the mechanisms of brain atrophy in multiple sclerosis (MS) related to focal lesions. VGM maps detect regional brain changes when comparing 2 time points on high resolution T1-weighted (T1w) magnetic resonace imaging (MRI). Two T1w MR datasets from 92 relapsing-remitting MS patients obtained 12 months apart were analysed with VGM. New lesions and volume changes of focal MS lesions as well as in the surrounding tissue were identified by visual inspection on colour coded VGM maps. Lesions were dichotomized in active and inactive lesions. Active lesions, defined by either new lesions (NL) (volume increase > 5% in VGM), chronic enlarging lesions (CEL) (pre-existent T1w lesions with volume increase > 5%), or chronic shrinking lesions (CSL) (pre-existent T1w lesions with volume reduction > 5%) in VGM, were accompanied by tissue shrinkage in surrounding and/or functionally related regions. Volume loss within the corpus callosum was highly correlated with the number of lesions in its close proximity. Volume loss in the lateral geniculate nucleus was correlated with lesions along the optic radiation. VGM analysis provides strong evidence that all active lesion types (NL, CEL, and CSL) contribute to brain volume reduction in the vicinity of lesions and/or in anatomically and functionally related areas of the brain.

A common brain network links development, aging, and vulnerability to disease.

Several theories link processes of development and aging in humans. In neuroscience, one model posits for instance that healthy age-related brain degeneration mirrors development, with the areas of the brain thought to develop later also degenerating earlier. However, intrinsic evidence for such a link between healthy aging and development in brain structure remains elusive. Here, we show that a data-driven analysis of brain structural variation across 484 healthy participants (8-85 y) reveals a largely--but not only--transmodal network whose lifespan pattern of age-related change intrinsically supports this model of mirroring development and aging. We further demonstrate that this network of brain regions, which develops relatively late during adolescence and shows accelerated degeneration in old age compared with the rest of the brain, characterizes areas of heightened vulnerability to unhealthy developmental and aging processes, as exemplified by schizophrenia and Alzheimer's disease, respectively. Specifically, this network, while derived solely from healthy subjects, spatially recapitulates the pattern of brain abnormalities observed in both schizophrenia and Alzheimer's disease. This network is further associated in our large-scale healthy population with intellectual ability and episodic memory, whose impairment contributes to key symptoms of schizophrenia and Alzheimer's disease. Taken together, our results suggest that the common spatial pattern of abnormalities observed in these two disorders, which emerge at opposite ends of the life spectrum, might be influenced by the timing of their separate and distinct pathological processes in disrupting healthy cerebral development and aging, respectively.

Assessment of perfusion deficits in ischemic stroke using 3D-GRASE arterial spin labeling magnetic resonance imaging with multiple inflow times.

BACKGROUND AND PURPOSE: Arterial spin labeling (ASL) MRI provides information on tissue perfusion by consecutive readout of labeled blood captured in arteries or the microvasculature without using contrast agents. METHODS: We used a single-shot 3D acquisition and readout technique for ASL with multiple inflow times (TI) to evaluate hemodynamic compromise and dynamics of arterial blood inflow expressed by the bolus arrival time (BAT). Thirty-six patients with ischemic stroke were examined with a standard multimodal MRI protocol including dynamic susceptibility contrast (DSC) and multi-TI ASL perfusion imaging. Time-to-peak maps were used to classify hemodynamic impairment as either hypo- or hyperperfusion. RESULTS: Overall there was a good agreement of ASL perfusion maps with DSC perfusion imaging on visual analysis. Correlations were found between ASL-BAT/(DSC-)Mean transit time (MTT) (r = .416; P < .01) and ASL-CBF/MTT (r = -.489; P < .01). Using ASL, BAT in ischemic territory was delayed by 55% (P = .001) in patients with hypoperfusion (n = 28); CBF was reduced by 39% (P<.001). All patients with hyperperfusion (n = 6) had higher CBF on ASL. CONCLUSIONS: The use of ASL with multiple TI allows the contrast-free assessment of hemodynamic impairment in ischemic stroke patients. Quantitative ASL perfusion analysis reliably demonstrates areas of delayed BAT and reduced CBF matching findings of DSC.

Biplanar MRI for the assessment of the spinal cord in multiple sclerosis.

OBJECTIVE: To investigate the entire spinal cord (SC) of multiple sclerosis (MS) patients with biplanar MRI and to relate these MRI findings to clinical functional scores. METHODS: Two hundred and two patients (140 women, 62 men 24-74 years, Expanded Disability Status Scale (EDSS) scores 0-7.5) were investigated clinically and with biplanar MRI. Sagittal and axial proton density weighted (PDw) and T2 weighted (T2w) images of the whole SC were obtained employing parallel imaging. Data were analyzed by consensus reading using a standardized reporting scheme. Different combinations of findings were compared to EDSS scores with Spearman's rank correlation coefficient (ρ). RESULTS: The combined analysis of sagittal and axial planes demonstrated slightly differing results in 97/202 (48%) patients. There were 9% additional lesions identified, leading to a higher lesion count in 28% of these patients, but also rejection of equivocal abnormality leading to a lower lesion count in 11% of patients. Considering both sagittal and axial images, SC abnormalities were found in 167/202 (83%) patients. When compared with EDSS scores, the combination of focal lesions, signs of atrophy and diffuse abnormalities showed a moderate correlation (ρ=0.52), that precludes its use for individual patient assessment. CONCLUSION: Biplanar MRI facilitates a comprehensive identification, localization, and grading of pathological SC findings in MS patients. This improves the confidence and utility of SC imaging.

Assessment of intracranial collateral flow by using dynamic arterial spin labeling MRA and transcranial color-coded duplex ultrasound.

BACKGROUND AND PURPOSE: To evaluate the potential of a new dynamic MRA sequence (DynAngio) based on arterial spin labeling for the assessment of intracranial collateral flow. METHODS: Twelve patients with unilateral internal carotid artery obstruction were investigated. Different patterns of collateral flow were compared between DynAngio, transcranial color-coded duplex ultrasound, and time-of-flight MRA. RESULTS: There was a good agreement between the methods, with sensitivities between 80% and 90%. Small collateral vessels were detected more frequently with DynAngio compared to time-of-flight MRA. CONCLUSIONS: DynAngio provides anatomic and similar to transcranial color-coded duplex ultrasound functional information on collateral flow for the assessment of intracranial hemodynamics.

Diffusion and perfusion MRI for the assessment of carotid atherosclerosis.

Atherosclerotic disease of the extracranial vessels is a frequent cause of cerebral ischemia and stroke. Many natural history studies and prospective treatment trials with large patient samples have focused on optimal patient assessment in regard to medical or interventional measures. Clinical decision making nowadays is largely based on the identification, visualization, and grading of the local stenosis, and the identification of neurologic symptoms related to carotid artery stenosis. MRI already has contributed considerably as many surgeons no longer require preoperative conventional contrast angiography but may use the combination of duplex ultrasound studies and MRA for visualization of the pathology. Besides MRA improvements, DWI and PWI are increasingly used in addition to conventional MR contrasts (PD, T2-, T1-weighted MRI) in attempts to gather information on tissue status and the pathophysiology of hemodynamic compromise and cerebral ischemia in patients with carotid artery stenosis. Obtaining background information using this array of MR data may eventually become a basis for optimal risk-benefit assessment in patients with carotid artery stenosis.