Carotid and aortic plaque imaging using 3D gradient-echo imaging and the three-point Dixon method with improved motion-sensitized driven-equilibrium (iMSDE)

BACKGROUND

We devised a method that combines the 3D-Dixon-gradientecho (GRE) method with an improved motion-sensitized driven-equilibrium (iMSDE) to suppress blood flow signals.

PURPOSE

The purpose of this study was to evaluate the effectiveness of the new method we developed plaque imaging method (3D-Dixon-GRE with the iMSDE method).

STUDY TYPE

Retrospective cohort.

POPULATION

Thirty-nine patients who underwent cervical plaque imaging.

FIELD STRENGTH/SEQUENCE

3.0 T/3D-GRE.

ASSESSMENT

Signal intensities of the common carotid artery, aorta, plaque, muscle, and subcutaneous fat were measured through the VISTA and the 3D-Dixon-GRE with iMSDE methods, and each contrast was calculated.

STATISTICAL TEST

Used the Mann Whitney U test. P-values below 0.05 were considered statistically significant.

RESULTS

Plaque and muscle contrast estimated through the VISTA method and 3D-Dixon-GRE with iMSDE method was 1.60 ± 0.96 and 2.04 ± 1.06, respectively, (P < 0.05). The contrast between the flow (common carotid artery and Aorta) and muscle according to the VISTA method and 3D-Dixon-GRE with iMSDE method was 0.24 ± 0.11 and 0.40 ± 0.12, respectively (P < 0.001). Finally, the mean contrast for subcutaneous fat and muscle at six locations was 3.05 ± 1.25 and 0.81 ± 0.23 for the VISTA method and 3D-Dixon-GRE with the iMSDE method, respectively (P < 0.001).

DATA CONCLUSION

Compared to the conventional method (VISTA), the 3D-Dixon-GRE with iMSDE method is preferable in relation to the fat suppression effect, but it is disadvantageous regarding blood flow signal suppression. Therefore, the 3D-Dixon-GRE with the iMSDE method could be considered useful for plaque imaging.

Predictive Value of Clinical, CSF and Vessel Wall MRI Variables in Diagnosing Primary Angiitis of the CNS

Background and Objectives

Without brain biopsy, there are limited diagnostic predictors to differentiate primary angiitis of the CNS (PACNS) from intracranial atherosclerotic disease (ICAD). We examined the utility of clinical, CSF, and quantitative vessel wall magnetic resonance imaging (VWMRI) variables in predicting PACNS from ICAD.

Methods

In this cross-sectional design, observational study, we reviewed electronic medical records to identify patients (18 years and older) who presented to our medical center between January 2015 and December 2021 for ischemic stroke due to intracranial vasculopathy. Patients with biopsy-proven PACNS, probable PACNS, or ICAD were included. Patients with secondary CNS vasculitis or no VWMRI data were excluded. On VWMRI, for each patient, a total of 20 vessel wall segments were analyzed for percent concentricity, percent irregularity, and concentricity to eccentricity (C/E) ratios. We also collected several clinical and CSF variables. Using logistic regression models, we assessed the diagnostic value of VWMRI, CSF, and clinical variables in predicting PACNS in patients with biopsy-proven disease. We then performed a sensitivity analysis to assess predictors of biopsy-proven and probable PACNS.

Results

Thirty-two patients with ICAD (54.2%) and 27 patients with PACNS (45.8%) were included. Of the patients with PACNS, 21 (77.8%) were not biopsied and considered probable PACNS. Twenty-four patients with ICAD (75%) and 6 biopsy-proven patients with PACNS (22.2%) showed large vessel involvement and were included in the primary analysis. Encephalopathy (odds ratio [OR], 7.60; 95% CI 1.07-54.09) and seizure (OR 23.00; 95% CI 1.77-298.45) were significantly associated with PACNS. All patients were included in the sensitivity analysis, in which headache significantly predicted PACNS (OR 7.60; 95% CI 1.07-54.09). In the primary analysis, for every 1 white blood cell/µL increase in CSF, there was a 47% higher odds of PACNS (OR 1.47; 95% CI 1.04-2.07). On VWMRI, a C/E ratio >1 (OR 115.00; 95% CI 6.11-2165.95), percent concentricity ≥50% (OR 55.00; 95% CI 4.13-732.71), and percent irregularity <50% (OR 55.00; 95% CI 4.13-732.71) indicated significantly higher odds of PACNS compared with ICAD.

Discussion

Our results suggest that quantitative VWMRI metrics, CSF pleocytosis, and clinical features of encephalopathy, seizure, and headache significantly predict a diagnosis of probable PACNS when compared with ICAD.

Simulation-based optimization and experimental comparison of intracranial T2-weighted DANTE-SPACE vessel wall imaging at 3T and 7T

PURPOSE

T2-weighted DANTE-SPACE (Delay Alternating with Nutation for Tailored Excitation - Sampling Perfection with Application optimized Contrasts using different flip angle Evolution) sequences facilitate non-invasive intracranial vessel wall imaging at 7T through simultaneous suppression of blood and CSF. However, the achieved vessel wall delineation depends closely on the selected sequence parameters, and little information is available about the performance of the sequence using more widely available 3T MRI. Therefore, in this paper a comprehensive DANTE-SPACE simulation framework is used for the optimization and quantitative comparison of T2-weighted DANTE-SPACE at both 7T and 3T.

METHODS

Simulations are used to propose optimized sequence parameters at both 3T and 7T. At 7T, an additional protocol which uses a parallel transmission (pTx) shim during the DANTE preparation for improved suppression of inflowing blood is also proposed. Data at both field strengths using optimized and literature protocols are acquired and quantitatively compared in six healthy volunteers.

RESULTS

At 7T, more vessel wall signal can be retained while still achieving sufficient CSF suppression by using fewer DANTE pulses than described in previous implementations. The use of a pTx shim during DANTE at 7T provides a modest further improvement to the inner vessel wall delineation. At 3T, aggressive DANTE preparation is required to achieve CSF suppression, resulting in reduced vessel wall signal. As a result, the achievable vessel wall definition at 3T is around half that of 7T.

CONCLUSION

Simulation-based optimization of DANTE parameters facilitates improved T2-weighted DANTE-SPACE contrasts at 7T. The improved vessel definition of T2-weighted DANTE-SPACE at 7T makes DANTE preparation more suitable for T2-weighted VWI at 7T than at 3T.

Radiomics-Based Predictive Nomogram for Assessing the Risk of Intracranial Aneurysms

Aneurysm wall enhancement (AWE) has the potential to be used as an imaging biomarker for the risk stratification of intracranial aneurysms (IAs). Radiomics provides a refined approach to quantify and further characterize AWE's textural features. This study examines the performance of AWE quantification combined with clinical information in detecting symptomatic IAs. Ninety patients harboring 104 IAs (29 symptomatic and 75 asymptomatic) underwent high-resolution magnetic resonance imaging (HR-MRI). The assessment of AWE was performed using two different methods: 3D-AWE mapping and composite radiomics-based score (RadScore). The dataset was split into training and testing subsets. The testing set was used to build two different nomograms using each modality of AWE assessment combined with patients' clinical information and aneurysm morphological data. Finally, each nomogram was evaluated on an independent testing set. A total of 22 radiomic features were significantly different between symptomatic and asymptomatic IAs. The 3D-AWE mapping nomogram achieved an area under the curve (AUC) of 0.77 (63% accuracy, 78% sensitivity, and 58% specificity). The RadScore nomogram exhibited a better performance, achieving an AUC of 0.83 (77% accuracy, 89% sensitivity, and 73% specificity). The comprehensive analysis of IAs with the quantification of AWE data through radiomic analysis, patient clinical information, and morphological aneurysm metrics achieves a high accuracy in detecting symptomatic IA status.

Associations between atherosclerotic luminal stenosis in the distal internal carotid artery and diffuse wall thickening in its upstream segment

OBJECTIVES

Significant atherosclerotic stenosis or occlusion in the distal internal carotid artery (ICA) may induce diffuse wall thickening (DWT) in the upstream arterial wall. This study aimed to assess the association of atherosclerotic steno-occlusive diseases in the distal ICA with DWT in the upstream ipsilateral ICA.

METHODS

Individuals with atherosclerotic stenosis in the distal ICA, detected by carotid MR vessel wall imaging using 3D pre- and post-contrast T1 volume isotropic turbo spin-echo acquisition (T1-VISTA) sequence, were enrolled. The associations of vessel wall thickening, the longitudinal extent of DWT, enhancement of the upstream ipsilateral ICA, and stenosis degree in the distal ICA were examined.

RESULTS

Totally 64 arteries in 55 patients with atherosclerotic steno-occlusive distal ICAs were included. Significant correlations were found between distal ICA stenosis and DWT in the petrous ICA (r = 0.422, p = 0.001), DWT severity (r = 0.474, p < 0.001), the longitudinal extent of DWT in the ICA (r = 0.671, p < 0.001), enhancement in the petrous ICA (r = 0.409, p = 0.001), and enhancement degree (r = 0.651, p < 0.001). In addition, high degree of enhancement was correlated with both increased wall thickness and increased prevalence of DWT in the petrous ICA (both p < 0.001).

CONCLUSIONS

DWT of the petrous ICA is commonly detected in patients with atherosclerotic steno-occlusive disease in the distal ICA. The degree of stenosis in the distal ICA is associated with wall thickening and its longitudinal extent in the upstream segments.

CLINICAL RELEVANCE STATEMENT

Diffuse wall thickening is a common secondary change in atherosclerotic steno-occlusive disease in the intracranial carotid. This phenomenon constitutes a confounding factor in the distinction between atherosclerosis and inflammatory vasculopathies, and could be reversed after alleviated atherosclerotic stenosis.

KEY POINTS

• Diffuse wall thickening of the petrous internal carotid artery is commonly detected in patients with atherosclerotic steno-occlusive disease in the distal internal carotid artery. • The phenomenon of diffuse wall thickening could be reversed after stenosis alleviation. • Carotid artery atherosclerosis with diffuse wall thickening should warrant a differential diagnosis from other steno-occlusive diseases, including moyamoya diseases and Takayasu aortitis.

Vessel Wall Imaging Features of Spontaneous Intracranial Carotid Artery Dissection

BACKGROUND AND OBJECTIVES

Intracranial dissection is an important cause of stroke often with nonspecific angiographic features. Vessel wall imaging (VWI) can detect dissections, but intracranial applications remain unvalidated by pathologic specimens. We sought to determine the ability of VWI to identify the rarely reported spontaneous intracranial carotid dissection (sICD) guided by postmortem validation.

METHODS

VWI features of sICD, validated by postmortem specimen analysis in 1 patient, included luminal enhancement within a hypoenhancing outer wall, narrowing the mid to distal ophthalmic (C6) segment, relatively sparing the communicating (C7) segment. VWI examinations were reviewed to identify patients (1) with matching imaging features, (2) no evidence of other vasculopathies (i.e., inflammatory, intracranial atherosclerotic disease [ICAD]), and (3) adequate image quality. These sICD VWI features were compared with those in patients with known ICAD causing similar narrowing of C6 and relative sparing of C7 by a Fisher exact test accounting for multiple samples.

RESULTS

Among 407 VWI examinations, 8 patients were identified with 14 sICDs, all women aged 30-56 years, 6 (75%) bilateral. All patients with sICD had risk factors of dissection (e.g., recently postpartum, fibromuscular dysplasia, and hypertension) and 3 (37.5%) had intracranial dissections elsewhere. Seven (87.5%) were diagnosed as moyamoya syndrome on initial angiography. Enhancing lesions varied from thin flap-like defects (n = 6) to thick tissue along the superolateral wall of the internal carotid artery, within the hypoenhancing outer wall. Compared with 10 intracranial carotid plaques in 8 patients with ICAD, sICD demonstrated stronger (84.6% vs 20.0%, p = 0.003-0.025) and more homogeneous (61.5% vs 0.0%, p = 0.005-0.069) enhancement and less positive remodeling (0.0% vs 60.0%, p = 0.004-0.09). T1 hyperintensity was identified in 5 sICDs in 3 patients but not identified in ICAD. Three patients with serial imaging (8- to 39.8-month maximum intervals) revealed little to no changes in stenosis, wall thickening, or enhancement.

DISCUSSION

sICD is distinguishable on VWI from ICAD by enhancement characteristics, less positive remodeling, and clinical parameters. These VWI features should raise suspicion especially in young women with risk factors of dissection. Temporal stability and a lack of T1 hyperintensity should not discourage diagnosing sICD.

Contrast-enhanced 3D black-blood magnetic resonance imaging for diagnosis of cerebral venous thrombosis

PURPOSE

Cerebral venous thrombosis (CVT) is often under-recognized on routine magnetic resonance imaging (MRI) examinations without concomitant magnetic resonance venography (MRV). Contrast-enhanced black-blood MRI (BBMRI) based on a three-dimensional T1-weighted variable-flip-angle turbo spin echo sequence, one of the sequences used routinely in our practice, has the potential for detection of thrombi in patients with CVT. The aim of this study is to evaluate the diagnostic performance and enhancement patterns of contrast-enhanced three-dimensional BBMRI for the diagnosis of CVT.

MATERIALS AND METHODS

Contrast-enhanced BBMRI and contrast-enhanced MRV sequences of 64 patients, acquired from June 2018 to January 2021, were retrospectively reviewed by neuroradiologists for detection of CVT in each venous sinus segment. Diagnostic performance values were calculated for contrast-enhanced BBMRI based on enhancement patterns.

RESULTS

Of 749 venous segments from 64 patients analyzed, CVT was demonstrated in 41 venous segments from 12 patients on contrast-enhanced MRV (CE MRV). Thick wall enhancement and total enhancement patterns were dominantly demonstrated in thrombosed segments. Compared with contrast-enhanced MRV, contrast-enhanced BBMRI had a patient-based sensitivity and specificity of 100% and 98.1%, respectively, and a segment-based sensitivity and specificity of 87.8% and 96.2%, respectively. The positive predictive value of contrast-enhanced BBMRI in detecting CVT was 92.3% (patient-based) and 57.1% (segment-based), and the negative predictive value was 100% (patient-based) and 99.3% (segment-based).

CONCLUSION

Contrast-enhanced BBMRI has high diagnostic performance in detection and diagnosis of CVT. This sequence may be useful to recognize CVT when dedicated CE MRV was not performed in patients with nonspecific neurological symptoms.

Temporal evolution of primary angiitis of the central nervous system (PACNS) on MRI following immunosuppressant treatment

PURPOSE

To systematically analyse the time course of vessel wall enhancement and associated stenosis in patients with primary angiitis of the central nervous system (PACNS) following immunosuppressive therapy.

MATERIAL AND METHODS

Two neuroradiologists retrospectively analysed MRIs of patients with PACNS seen at the Bern University Hospital and the St. Gallen Cantonal Hospital between 2015 and 2020. MRIs were examined for the presence of vessel wall enhancement, length of vessel wall enhancement (mm), circumferential extent of enhancement (degree) and degree of stenosis (%). Descriptive statistics and measurements of interobserver reliability were obtained. To investigate the temporal profiles of the variables following the commencement of immunosuppressant treatment, four series of Bayesian generalised multi-level models were generated.

RESULTS

A total of 23 patients with 43 affected vessels identified from 209 MRI exams were evaluated (mean follow-up: 715 days, standard deviation ± 487 days), leading to a complete dataset of 402 entries. Vessel wall enhancement and circumferential extent of enhancement decreased for approximately 1 year after the initiation of immunosuppressant therapy. Changes were more pronounced in younger patients. Disappearance of vessel wall enhancement (in at least one vessel) was seen in about half of patients after a median of 172 days interquartile range 113-244, minimum 54 days, maximum 627 days.

CONCLUSIONS

This study evaluated the typical time course of vessel wall enhancement in patients with PACNS. Our results could be a useful reference for radiologists and clinicians interpreting follow-up imaging in patients with PACNS.

CRITICAL RELEVANCE STATEMENT

Routine clinical exams can be interpreted with more confidence when radiologists are aware of the typical temporal evolution of vessel wall enhancement in patients with primary angiitis of the central nervous system after initiation of immunosuppressive therapy.

KEY POINTS

Few data exist for vessel wall imaging of primary angiitis of the central nervous system. Following immunosuppressant therapy, vessel wall enhancement decreases for approximately one year. These results may serve as a reference for radiologists performing follow-up imaging.

CT texture analysis of vertebrobasilar artery calcification to identify culprit plaques

Objectives

The aim of this study was to extract radiomic features from vertebrobasilar artery calcification (VBAC) on head computed tomography (CT) images and investigate its diagnostic performance to identify culprit lesions responsible for acute cerebral infarctions.

Methods

Patients with intracranial atherosclerotic disease who underwent vessel wall MRI (VW-MRI) and head CT examinations from a single center were retrospectively assessed for VBAC visual and textural analyses. Each calcified plaque was classified by the likelihood of having caused an acute cerebral infarction identified on VW-MRI as culprit or non-culprit. A predefined set of texture features extracted from VBAC segmentation was assessed using the minimum redundancy and maximum relevance method. Five key features were selected to integrate as a radiomic model using logistic regression by the Aikaike Information Criteria. The diagnostic value of the radiomic model was calculated for discriminating culprit lesions over VBAC visual assessments.

Results

A total of 1,218 radiomic features were extracted from 39 culprit and 50 non-culprit plaques, respectively. In the VBAC visual assessment, culprit plaques demonstrated more observed presence of multiple calcifications, spotty calcification, and intimal predominant calcification than non-culprit lesions (all p < 0.05). In the VBAC texture analysis, 55 (4.5%) of all extracted features were significantly different between culprit and non-culprit plaques (all p < 0.05). The radiomic model incorporating 5 selected features outperformed multiple calcifications [AUC = 0.81 with 95% confidence interval (CI) of 0.72, 0.90 vs. AUC = 0.61 with 95% CI of 0.49, 0.73; p = 0.001], intimal predominant calcification (AUC = 0.67 with 95% CI of 0.58, 0.76; p = 0.04) and spotty calcification (AUC = 0.62 with 95% CI of 0.52, 0.72; p = 0.005) in the identification of culprit lesions.

Conclusion

Culprit plaques in the vertebrobasilar artery exhibit distinct calcification radiomic features compared to non-culprit plaques. CT texture analysis of VBAC has potential value in identifying lesions responsible for acute cerebral infarctions, which may be helpful for stroke risk stratification in clinical practice.

Radiomics-Based Predictive Nomogram for Assessing the Risk of Intracranial Aneurysms

Background

Aneurysm wall enhancement (AWE) has the potential to be used as an imaging biomarker for the risk stratification of intracranial aneurysms (IAs). Radiomics provides a refined approach to quantify and further characterize AWE's textural features. This study examines the performance of AWE quantification combined with clinical information in detecting symptomatic IAs.

Methods

Ninety patients harboring 104 IAs (29 symptomatic and 75 asymptomatic) underwent high-resolution magnetic resonance imaging (HR-MRI). The assessment of AWE was performed using two different methods: 3D-AWE mapping and composite radiomics-based score (RadScore). The dataset was split into training and testing subsets. The testing set was used to build two different nomograms using each modality of AWE assessment combined with patients' demographic information and aneurysm morphological data. Finally, each nomogram was evaluated on an independent testing set.

Results

A total of 22 radiomic features were significantly different between symptomatic and asymptomatic IAs. The 3D-AWE Mapping nomogram achieved an area under the curve (AUC) of 0.77 (63% accuracy, 78% sensitivity and 58% specificity). The RadScore nomogram exhibited a better performance, achieving an AUC of 0.83 (77% accuracy, 89% sensitivity and 73% specificity).

Conclusions

Combining AWE quantification through radiomic analysis with patient demographic data in a clinical nomogram achieved high accuracy in detecting symptomatic IAs.

Implementation of a Clinical Vessel Wall MR Imaging Program at an Academic Medical Center

BACKGROUND AND PURPOSE

The slow adoption of new advanced imaging techniques into clinical practice has been a long-standing challenge. Principles of implementation science and the reach, effectiveness, adoption, implementation, maintenance (RE-AIM) framework were used to build a clinical vessel wall imaging program at an academic medical center.

MATERIALS AND METHODS

Six phases for implementing a clinical vessel wall MR imaging program were contextualized to the RE-AIM framework. Surveys were designed and distributed to MR imaging technologists and clinicians. Effectiveness was measured by surveying the perceived diagnostic value of vessel wall imaging among MR imaging technologists and clinicians, trends in case volumes in the clinical vessel wall imaging examination, and the number of coauthored vessel wall imaging-focused publications and abstracts. Adoption and implementation were measured by surveying stakeholders about workflow. Maintenance was measured by surveying MR imaging technologists on the value of teaching materials and online tip sheets. The Integration dimension was measured by the number of submitted research grants incorporating vessel wall imaging protocols. Feedback during the implementation phases and solicited through the survey is qualitatively summarized. Quantitative results are reported using descriptive statistics.

RESULTS

Six phases of the RE-AIM framework focused on the following: 1) determining patient and disease representation, 2) matching resource availability and patient access, 3) establishing vessel MR wall imaging (VWI) expertise, 4) forming interdisciplinary teams, 5) iteratively refining workflow, and 6) integrating for maintenance and scale. Survey response rates were 48.3% (MR imaging technologists) and 71.4% (clinicians). Survey results showed that 90% of the MR imaging technologists agreed that they understood how vessel wall MR imaging adds diagnostic value to patient care. Most clinicians (91.3%) reported that vessel wall MR imaging results changed their diagnostic confidence or patient management. Case volumes of clinical vessel wall MR imaging performed from 2019 to 2022 rose from 22 to 205 examinations. Workflow challenges reported by MR imaging technologists included protocoling examinations and scan length. Feedback from ordering clinicians included the need for education about VWI indications, limitations, and availability. During the 3-year implementation period of the program, the interdisciplinary teams coauthored 27 publications and abstracts and submitted 13 research grants.

CONCLUSIONS

Implementation of a clinical imaging program can be successful using the principles of the RE-AIM framework. Through iterative processes and the support of interdisciplinary teams, a vessel wall MR imaging program can be integrated through a dedicated clinical pipeline, add diagnostic value, support educational and research missions at an academic medical center, and become a center for excellence.

MR Vessel Wall Imaging for Atherosclerosis and Vasculitis

Conventional imaging modalities, such as computed tomography angiography, MR angiography, transcranial Doppler ultrasonography, and digital subtraction angiography, are utilized in evaluating intraluminal or intravascular pathology of the intracranial vessels. Limitations of luminal imaging techniques can lead to inaccurate diagnosis, evaluation, and risk stratification, as many cerebrovascular pathologies contain an extrinsic vessel wall component. Furthermore, vessel wall imaging can provide information regarding extent, treatment response, and biopsy targets for vasculitis cases. Overall, while vessel wall imaging can provide robust data regarding intracranial pathologies, further prospective, multicenter studies are required to improve diagnostic application and accuracy.

Imaging Review of Pediatric Monogenic CNS Vasculopathy with Genetic Correlation

Monogenic cerebral vasculopathy is a rare but progressively recognizable cause of pediatric cerebral vasculopathy manifesting as early as fetal life. These monogenic cerebral vasculopathies can be silent or manifest variably as fetal or neonatal distress, neurologic deficit, developmental delay, cerebral palsy, seizures, or stroke. The radiologic findings can be nonspecific, but the presence of disease-specific cerebral and extracerebral imaging features can point to a diagnosis and guide genetic testing, allowing targeted treatment. The authors review the existing literature describing the frequently encountered and rare monogenic cerebral vascular disorders affecting young patients and describe the relevant pathogenesis, with an attempt to categorize them based on the defective step in vascular homeostasis and/or signaling pathways and characteristic cerebrovascular imaging findings. The authors also highlight the role of imaging and a dedicated imaging protocol in identification of distinct cerebral and extracerebral findings crucial in the diagnostic algorithm and selection of genetic testing. Early and precise recognition of these entities allows timely intervention, preventing or delaying complications and thereby improving quality of life. It is also imperative to identify the specific pathogenic variant and pattern of inheritance for satisfactory genetic counseling and care of at-risk family members. Last, the authors present an image-based approach to these young-onset monogenic cerebral vasculopathies that is guided by the size and predominant radiologic characteristics of the affected vessel with reasonable overlap. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Glymphatic-lymphatic coupling: assessment of the evidence from magnetic resonance imaging of humans

The discoveries that cerebrospinal fluid participates in metabolic perivascular exchange with the brain and further drains solutes to meningeal lymphatic vessels have sparked a tremendous interest in translating these seminal findings from animals to humans. A potential two-way coupling between the brain extra-vascular compartment and the peripheral immune system has implications that exceed those concerning neurodegenerative diseases, but also imply that the central nervous system has pushed its immunological borders toward the periphery, where cross-talk mediated by cerebrospinal fluid may play a role in a range of neoplastic and immunological diseases. Due to its non-invasive approach, magnetic resonance imaging has typically been the preferred methodology in attempts to image the glymphatic system and meningeal lymphatics in humans. Even if flourishing, the research field is still in its cradle, and interpretations of imaging findings that topographically associate with reports from animals have yet seemed to downplay the presence of previously described anatomical constituents, particularly in the dura. In this brief review, we illuminate these challenges and assess the evidence for a glymphatic-lymphatic coupling. Finally, we provide a new perspective on how human brain and meningeal clearance function may possibly be measured in future.

Imaging of intracranial arterial disease: a comparison between MRI and unenhanced CT

Background and purpose

Arterial calcifications on unenhanced CT scans and vessel wall lesions on MRI are often used interchangeably to portray intracranial arterial disease. However, the extent of pathology depicted with each technique is unclear. We investigated the presence and distribution of these two imaging findings in patients with a history of cerebrovascular disease.

Materials and methods

We analyzed CT and MRI data from 78 patients admitted for stroke or TIA at our institution. Vessel wall lesions were assessed on 7 T MRI sequences, while arterial calcifications were assessed on CT scans. The number of vessel wall lesions, severity of intracranial internal carotid artery (iICA) calcifications, and overall presence and distribution of the two imaging findings were visually assessed in the intracranial arteries.

Results

At least one vessel wall lesion or arterial calcification was assessed in 69 (88%) patients. Only the iICA and vertebral arteries (VA) showed a substantial number of both calcifications and vessel wall lesions. The other vessels showed almost exclusively vessel wall lesions. The number of vessel wall lesions was associated with the severity of iICA calcification (p = 0.013).

Conclusions

The number of vessel wall lesions increases with the severity of iICA calcifications. Nonetheless, the distribution of vessel wall lesions on MRI and arterial calcifications on CT shows remarkable differences. These findings support the need for a combined approach to examine intracranial arterial disease.

Epidemiology, Pathophysiology, and Imaging of Atherosclerotic Intracranial Disease

Intracranial atherosclerotic disease (ICAD) is one of the most common causes of stroke worldwide. Among people with stroke, those of East Asia descent and non-White populations in the United States have a higher burden of ICAD-related stroke compared with Whites of European descent. Disparities in the prevalence of asymptomatic ICAD are less marked than with symptomatic ICAD. In addition to stroke, ICAD increases the risk of dementia and cognitive decline, magnifying ICAD societal burden. The risk of stroke recurrence among patients with ICAD-related stroke is the highest among those with confirmed stroke and stenosis ≥70%. In fact, the 1-year recurrent stroke rate of >20% among those with stenosis >70% is one of the highest rates among common causes of stroke. The mechanisms by which ICAD causes stroke include plaque rupture with in situ thrombosis and occlusion or artery-to-artery embolization, hemodynamic injury, and branch occlusive disease. The risk of stroke recurrence varies by the presumed underlying mechanism of stroke, but whether techniques such as quantitative magnetic resonance angiography, computed tomographic angiography, magnetic resonance perfusion, or transcranial Doppler can help with risk stratification beyond the degree of stenosis is less clear. The diagnosis of ICAD is heavily reliant on lumen-based studies, such as computed tomographic angiography, magnetic resonance angiography, or digital subtraction angiography, but newer technologies, such as high-resolution vessel wall magnetic resonance imaging, can help distinguish ICAD from stenosing arteriopathies.

Neuroimaging of Infectious Vasculopathy

Vasculitis is a complication of several infectious diseases affecting the central nervous system, which may result in ischemic and/or hemorrhagic stroke, transient ischemic attack, and aneurysm formation. Infectious agents may directly infect the endothelium causing vasculitis or indirectly affect the vessel wall through an immunological cascade. Clinical manifestations usually overlap with those of noninfectious vascular diseases, making diagnosis challenging. Neuroimaging enables the identification of inflammatory changes in intracranial vasculitis. In this article, we review the imaging features of infectious vasculitis of bacterial, viral, fungal and parasitic causes.

Emerging Concept of Intracranial Arterial Diseases: The Role of High Resolution Vessel Wall MRI

Intracranial arterial disease (ICAD) is a heterogeneous condition characterized by distinct pathologies, including atherosclerosis. Advances in magnetic resonance technology have enabled the visualization of intracranial arteries using high-resolution vessel wall imaging (HR-VWI). This review summarizes the anatomical, embryological, and histological differences between the intracranial and extracranial arteries. Next, we review the heterogeneous pathophysiology of ICAD, including atherosclerosis, moyamoya or RNF213 spectrum disease, intracranial dissection, and vasculitis. We also discuss how advances in HR-VWI can be used to differentiate ICAD etiologies. We emphasize that one should consider clinical presentation and timing of imaging in the absence of pathology-radiology correlation data. Future research should focus on understanding the temporal profile of HR-VWI findings and developing quantitative interpretative approaches to improve the decision-making and management of ICAD.

Plaque Evolution and Vessel Wall Remodeling of Intracranial Arteries: A Prospective, Longitudinal Vessel Wall MRI Study

BACKGROUND

Progression of intracranial atherosclerotic disease (ICAD) is associated with ischemic stroke events and can be quantified with three-dimensional (3D) intracranial vessel wall (IVW) MRI. However, longitudinal 3D IVW studies are limited and ICAD evolution remains relatively unknown.

PURPOSE

To evaluate ICAD changes longitudinally and to characterize the imaging patterns of atherosclerotic plaque evolution.

STUDY TYPE

Prospective.

POPULATION

37 patients (69 ± 12 years old, 12 females) with angiography confirmed ICAD.

FIELD STRENGTH/SEQUENCE

3.0T/3D time-of-flight gradient echo sequence and T1- and proton density-weighted fast spin echo sequences.

ASSESSMENT

Each patient underwent baseline and 1-year follow-up IVW. Then, IVW data from both time points were jointly preprocessed using a multitime point, multicontrast, and multiplanar viewing workflow (known as MOCHA). Lumen and outer wall of plaques were traced and measured, and plaques were then categorized into progression, stable, and regression groups based on changes in plaque wall thickness. Patient demographic and clinical data were collected. Culprit plaques were identified based on cerebral ischemic infarcts.

STATISTICAL TESTS

Generalized estimating equations-based linear and logistic regressions were used to assess associations between vascular risk factors, medications, luminal stenosis, IVW plaque imaging features, and longitudinal changes. A two-sided P-value<0.05 was considered statistically significant.

RESULTS

Diabetes was significantly associated with ICAD progression, resulting in 6.6% decrease in lumen area and 6.7% increase in wall thickness at 1-year follow-up. After accounting for arterial segments, baseline contrast enhancement predicted plaque progression (odds ratio = 3.61). Culprit plaques experienced an average luminal expansion of 10.9% after 1 year. 74% of the plaques remained stable during follow-up. The regression group (18 plaques) showed significant increase in minimum lumen area (from 7.4 to 8.3 mm2 ), while the progression group (13 plaques) showed significant decrease in minimum lumen area (from 5.4 to 4.3 mm2 ).

DATA CONCLUSION

Longitudinal 3D IVW showed ICAD remodeling on the lumen side. Culprit plaques demonstrated longitudinal luminal expansion compared with their non-culprit counterparts. Baseline plaque contrast enhancement and diabetes mellitus were found to be significantly associated with ICAD changes.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 3.

Black blood MRI sequences in the acute management of ruptured and unruptured intracranial aneurysms

We present an illustrative case series in which high spatial resolution black blood (BB) MRI sequences were used as an adjunct in the acute management of intracranial aneurysms with diagnostic uncertainty regarding rupture status. Several acute management dilemmas are discussed including the surveillance of previously treated ruptured intracranial aneurysms, identifying culprit lesion(s) amongst multiple ruptured intracranial aneurysms, and risk stratifying incidental unruptured intracranial aneurysms. We present our experience which supports the evaluation of this vessel wall imaging technique in larger multi-centre observational studies. MR imaging was performed on a 3.0 Tesla Siemens Somatom Vida system and sequences used included: Susceptibility Weighted Imaging, Diffusion Weighted Imaging & 3D T1 pre- and post-contrast-enhanced BB sequences.

3D phase-sensitive inversion recovery sequence for intracranial vertebrobasilar artery dissection

BACKGROUND

T1-weighted 3D turbo spin echo (T1W-3D-TSE) sequences with variable refocusing flip angle are commonly used to diagnose intracranial vertebrobasilar artery dissection (iVAD). However, magnetic susceptibility artifacts of the cavernous sinus may cause loss of the basilar and vertebral arteries. This study investigated the effectiveness of a 3D phase-sensitive inversion recovery (3D-PSIR) sequence in reducing magnetic susceptibility artifacts in the cavernous sinus, and its imaging findings for iVAD.

METHODS

Twelve volunteers and eleven patients with iVAD were included. Magnetic resonance imaging (MRI) was performed using a 3.0-T MRI system. 3D-PSIR and T1W-3D-TSE sequences were used. Vessel wall defects and contrast-to-noise ratio (CNR) were evaluated. The MRI findings were visually evaluated.

RESULTS

In the 3D-PSIR images, one volunteer (8 %) had vessel wall defects, and five (42 %) had vessel wall defects (p = 0.046) in the T1W-3D-TSE images. CNR was higher in 3D-PSIR images for vessel wall-to-lumen, whereas it was higher in T1W-3D-TSE images for vessel wall-to-CSF (p < 0.001). Visual evaluation revealed similar MRI findings between the two sequences.

CONCLUSIONS

The 3D-PSIR sequence may be able to improve the vessel wall defects and achieve MRI findings comparable to those of the T1W-3D-TSE sequence in iVAD. The 3D-PSIR sequence can be a useful tool for the imaging-based diagnosis of iVAD.

Use of a Commercial 7-T MRI Scanner for Clinical Brain Imaging: Indications, Protocols, Challenges, and Solutions-A Single-Center Experience

The first commercially available 7-T MRI scanner (Magnetom Terra) was approved by the FDA in 2017 for clinical imaging of the brain and knee. After initial protocol development and sequence optimization efforts in volunteers, the 7-T system, in combination with an FDA-approved 1-channel transmit/32-channel receive array head coil, can now be routinely used for clinical brain MRI examinations. The ultrahigh field strength of 7-T MRI has the advantages of improved spatial resolution, increased SNR, and increased CNR but also introduces an array of new technical challenges. The purpose of this article is to describe an institutional experience with the use of the commercially available 7-T MRI scanner for routine clinical brain imaging. Specific clinical indications for which 7-T MRI may be useful for brain imaging include brain tumor evaluation with possible perfusion imaging and/or spectroscopy, radiotherapy planning; evaluation of multiple sclerosis and other demyelinating diseases, evaluation of Parkinson disease and guidance of deep brain stimulator placement, high-detail intracranial MRA and vessel wall imaging, evaluation of pituitary pathology, and evaluation of epilepsy. Detailed protocols, including sequence parameters, for these various indications are presented, and implementation challenges (including artifacts, safety, and side effects) and potential solutions are explored.

Visualizing Cerebral Small Vessel Degeneration During Aging and Diseases Using Magnetic Resonance Imaging

Cerebral small vessel disease is a major contributor to brain disorders in older adults. It is associated with a much higher risk of stroke and dementia. Due to a lack of clinical and fluid biomarkers, diagnosing and grading small vessel disease are highly dependent on magnetic resonance imaging. In the past, researchers mostly used brain parenchymal imaging markers to represent small vessel damage, but the relationships between these surrogate markers and small vessel pathologies are complex. Recent progress in high-resolution magnetic resonance imaging methods, including time-of-flight MR angiography, phase-contrast MR angiography, black blood vessel wall imaging, susceptibility-weighted imaging, and contrast-enhanced methods, allow for direct visualization of cerebral small vessel structures. They could be powerful tools for understanding aging-related small vessel degeneration and improving disease diagnosis and treatment. This article will review progress in these imaging techniques and their application in aging and disease studies. Some challenges and future directions are also discussed. EVIDENCE LEVEL: 4. TECHNICAL EFFICACY: 3.

Vessel-wall MRI in primary headaches: The role of neurogenic inflammation

OBJECTIVE

The purpose of this study was to investigate if vessel-wall magnetic resonance imaging (VW-MRI) could differentiate among primary headaches disorders, such as migraine and cluster headache (CH), and detect the presence of neurogenic inflammation.

BACKGROUND

The pathophysiology of primary headaches disorders is complex and not completely clarified. The activation of nociceptive trigeminal afferents through the release of vasoactive neuropeptides, termed "neurogenic inflammation," has been hypothesized. VW-MRI can identify vessel wall changes, reflecting the inflammatory remodeling of the vessel walls despite different etiologies.

METHODS

In this case series, we enrolled seven patients with migraine and eight patients with CH. They underwent a VW-MRI study before and after the intravenous administration of contrast medium, during and outside a migraine attack or cluster period. Two expert neuroradiologists analyzed the magnetic resonance imaging (MRI) studies to identify the presence of vessel wall enhancement or other vascular abnormalities.

RESULTS

Fourteen out of 15 patients had no enhancement. One out of 15, with migraine, showed a focal parietal enhancement in the intracranial portion of a vertebral artery, unmodified during and outside the attack, thus attributable to atherosclerosis. No contrast enhancement attributable to neurogenic inflammation was observed in VW-MRI, both during and outside the attack/cluster in all patients. Moreover, MRI angiography registered slight diffuse vasoconstriction in one of seven patients with migraine during the attack and in one of eight patients with cluster headache during the cluster period; both patients had taken triptans as symptomatic therapy for pain.

CONCLUSIONS

These preliminary results suggest that VW-MRI studies are negative in patients with primary headache disorders even during migraine attacks or cluster periods. The VW-MRI studies did not detect signs of neurogenic inflammation in the intracranial intradural vessels of patients with migraine or CH.

High-resolution magnetic resonance imaging of acute intracranial artery thrombus

BACKGROUND AND PURPOSE

The development of high-resolution magnetic resonance imaging (HR-MRI) has enabled submillimeter-level evaluation of intracranial artery plaque and luminal thrombus. We sought to investigate the value of HR-MRI in assessing the pathogenesis of acute intracranial artery thrombus.

METHODS

We examined the presence of intracranial thrombus on three-dimensional T1-weighted HR-MRI in acute ischemic stroke patients with intracranial artery occlusion on magnetic resonance angiography. We defined two thrombus-related HR-MRI features (peri-thrombus plaque and distal residual flow beyond the thrombus) and analyzed their association with potential embolic sources.

RESULTS

Luminal thrombus and a shrunken artery without luminal thrombus were detected in 162 (96.4%) and six (3.6%) of 168 patients with intracranial artery occlusion, respectively. Among 111 patients with culprit major artery thrombus, peri-thrombus plaques were observed in 46.8% and distal residual flow beyond the thrombus in 64.0%. Patients with peri-thrombus plaque had a higher prevalence of diabetes (44.2% vs. 25.4%; p = 0.037), a lower prevalence of potential sources of cardioembolism (0% vs. 16.9%; p = 0.002), and a nonsignificantly lower prevalence of potential embolic sources from extracranial arteries (9.6% vs. 20.3%; p = 0.186) than those without. Patients with distal residual flow beyond the thrombus had a lower prevalence of potential sources of cardioembolism (1.4% vs. 22.5%; p < 0.001) and smaller infarct volumes (5.0 [1.4-12.7] mL vs. 16.6 [2.4-94.6] mL; p = 0.012) than those without.

CONCLUSIONS

Our study showed that HR-MRI helps clarify the pathogenesis of acute intracranial artery thrombus. The presence of peri-thrombus plaque and distal residual flow beyond the thrombus favor the stroke mechanism of atherosclerosis rather than cardioembolism.

Obstructive sleep apnea: a major risk factor for COVID-19 encephalopathy?

BACKGROUND

This study evaluates the impact of high risk of obstructive sleep apnea (OSA) on coronavirus disease 2019 (COVID-19) acute encephalopathy (AE).

METHODS

Between 3/1/2020 and 11/1/2021, 97 consecutive patients were evaluated at the Geneva University Hospitals with a neurological diagnosis of COVID-19 AE. They were divided in two groups depending on the presence or absence of high risk for OSA based on the modified NOSAS score (mNOSAS, respectively ≥ 8 and < 8). We compared patients' characteristics (clinical, biological, brain MRI, EEG, pulmonary CT). The severity of COVID-19 AE relied on the RASS and CAM scores.

RESULTS

Most COVID-19 AE patients presented with a high mNOSAS, suggesting high risk of OSA (> 80%). Patients with a high mNOSAS had a more severe form of COVID-19 AE (84.8% versus 27.8%), longer mean duration of COVID-19 AE (27.9 versus 16.9 days), higher mRS at discharge (≥ 3 in 58.2% versus 16.7%), and increased prevalence of brain vessels enhancement (98.1% versus 20.0%). High risk of OSA was associated with a 14 fold increased risk of developing a severe COVID-19 AE (OR = 14.52).

DISCUSSION

These observations suggest an association between high risk of OSA and COVID-19 AE severity. High risk of OSA could be a predisposing factor leading to severe COVID-19 AE and consecutive long-term sequalae.

Correlation of the middle cerebral artery atherosclerotic plaque characteristics with ischemic stroke recurrence: a vessel wall magnetic resonance imaging study

This study aims to analyze the imaging features of atherosclerotic plaques in the middle cerebral artery (MCA) of patients with recurrent ischemic stroke using vessel wall magnetic resonance imaging (VWMRI) and investigate the correlation between these imaging features and the recurrence of ischemic stroke. Consecutive patients with ischemic stroke caused by atherosclerotic stenosis of the MCA were collected. The patients were divided into recurrent and non-recurrent ischemic stroke groups. We obtained VWMRI images of MCA plaques using 3.0T MRI by black-blood sequences, and the differences in VWMRI characteristics and clinical information between the two groups were compared. A binary Logistic regression model was used to analyze the VWMRI characteristics and clinical information related to ischemic stroke recurrence. 179 patients were collected from August 2018 to May 2020, and 81 patients were included in the study. The recurrent ischemic stroke group patients had a higher stenosis rate (0.69 vs 0.64). Meanwhile, the rate of centripetal wall thickening was significantly higher in patients with recurrent ischemic stroke (33.3% vs 11.7%). Binary Logistic regression analysis showed that sex (P=0.036, OR:2.983, CI:1.075-8.279), stenosis rate (P=0.038, OR:148.565, CI:1.331-16583.631), and vessel wall thickening pattern (P=0.012, OR:0.171, CI:0.043-0.678) were related to ischemic stroke recurrence. The patients with ischemic stroke caused by atherosclerotic stenosis of MCA, female patients, and those with concentric wall thickening and a high degree of stenosis have a higher risk of recurrence. Our results suggest that VWMRI is a valuable tool for predicting the risk of ischemic stroke recurrence in patients with MCA plaques.

MR Imaging for Intracranial Vessel Wall Imaging: Pearls and Pitfalls

Conventional vascular imaging methods have primarily focused on evaluating the vascular lumen. However, these techniques are not intended to evaluate vessel wall abnormalities where many cerebrovascular pathologies reside. With increased interest for the visualization and study of the vessel wall, high-resolution vessel wall imaging (VWI) has gained traction.Over the past two decades, there has been a rapid increase in number of VWI publications with improvements in imaging techniques and expansion on clinical applications. With increasing utility and interest in VWI, application of proper protocols and understanding imaging characteristics of vasculopathies are important for the interpreting radiologists to understand.

Intracranial vessel wall magnetic resonance imaging features of infectious vasculitis

Vasculitis is a complication of several infectious diseases affecting the central nervous system, which may result in ischemic and/or hemorrhagic stroke, transient ischemic attack, and aneurysm formation. The infectious agent may directly infect the endothelium, causing vasculitis, or indirectly affect the vessel wall through an immunological mechanism. The clinical manifestations of these complications usually overlap with those of non-infectious vascular diseases, making diagnosis challenging. Intracranial vessel wall magnetic resonance imaging (VWI) enables the evaluation of the vessel wall and the diseases that affect it, providing diagnostic data beyond luminal changes and enabling the identification of inflammatory changes in cerebral vasculitis. This technique demonstrates concentric vessel wall thickening and gadolinium enhancement, associated or not with adjacent brain parenchymal enhancement, in patients with vasculitis of any origin. It permits the detection of early alterations, even before a stenosis occurs. In this article, we review the intracranial vessel wall imaging features of infectious vasculitis of bacterial, viral, and fungal etiologies.

Evaluation of vessel-wall contrast-enhancement on high-resolution MRI in European patients with Moyamoya disease

OBJECTIVES

Data regarding MR vessel-wall imaging (VWI) in patients with Moyamoya disease (MMD) is sparse, particularly in non-asian cohorts. We contribute data regarding the frequency of vessel wall contrast-enhancement (VW-CE) and its potential clinical significance in a European patient group.

MATERIALS AND METHODS

Patients with a diagnosis of MMD who were examined by VWI were included in the study. VW-CE of stenoocclusive lesions of the terminal internal carotid artery and/or its proximal branches was rated qualitatively. Changes of VW-CE on available follow-up were recorded. VW-CE was correlated with diffusion-restricted lesions and magnetic resonance angiography (MRA) findings.

RESULTS

Eleven patients (eight female, three male) were included. Twenty-eight stenoocclusive lesions were analyzed, of which 16 showed VW-CE (57.1%). VW-CE was mostly concentric (n=15), rather than eccentric (n=1). In all three patients in whom follow-up VWI was available, changes of VW-CE were documented. Diffusion-restricted lesions were more frequently related to stenoocclusive lesions with VW-CE (n=9) than without VW-CE (n=2), bordering statistical significance. The affected arteries were assessed as stenotic and as occluded in 14 cases each and VW-CE was seen significantly more often in stenotic (n=12) than in occluded arteries (n=4). No correlation was found between the presence of VW-CE and moyamoya stages determined by MRA.

CONCLUSIONS

Our data suggest that concentric VW-CE is a relatively frequent finding in European MMD patients. VW-CE may change over time and occur in certain stages, possibly representing "active stenosing". Larger studies are needed to validate these findings and determine the clinical relevance of VW-CE in MMD.

The incomplete circle of Willis is associated with vulnerable intracranial plaque features and acute ischemic stroke

BACKGROUND

The circle of Willis (CoW) plays a significant role in intracranial atherosclerosis (ICAS). This study investigated the relationship between different types of CoW, atherosclerosis plaque features, and acute ischemic stroke (AIS).

METHODS

We investigated 97 participants with AIS or transient ischemic attacks (TIA) underwent pre- and post-contrast 3T vessel wall cardiovascular magnetic resonance within 7 days of the onset of symptoms. The culprit plaque characteristics (including enhancement grade, enhancement ratio, high signal in T1, irregularity of plaque surface, and normalized wall index), and vessel remodeling (including arterial remodeling ratio and positive remodeling) for lesions were evaluated. The anatomic structures of the anterior and the posterior sections of the CoW (A-CoW and P-CoW) were also evaluated. The plaque features were compared among them. The plaque features were also compared between AIS and TIA patients. Finally, univariate and multivariate regression analysis was performed to evaluate the independent risk factors for AIS.

RESULT

Patients with incomplete A-CoW showed a higher plaque enhancement ratio (P = 0.002), enhancement grade (P = 0.01), and normalized wall index (NWI) (P = 0.018) compared with the patients with complete A-CoW. A higher proportion of patients with incomplete symptomatic P-CoW demonstrated more culprit plaques with high T1 signals (HT1S) compared with those with complete P-CoW (P = 0.013). Incomplete A-CoW was associated with a higher enhancement grade of the culprit plaques [odds ratio (OR):3.84; 95% CI: 1.36-10.88, P = 0.011], after adjusting for clinical risk factors such as age, sex, smoking, hypertension, hyperlipemia, and diabetes mellitus. Incomplete symptomatic P-CoW was associated with a higher probability of HT1S (OR:3.88; 95% CI: 1.12-13.47, P = 0.033), after adjusting for clinical risk factors such as age, sex, smoking, hypertension, hyperlipemia, and diabetes mellitus. Furthermore, an irregularity of the plaque surface (OR: 6.24; 95% CI: 2.25-17.37, P < 0.001), and incomplete symptomatic P-CoW (OR: 8.03, 95% CI: 2.43-26.55, P = 0.001) were independently associated with AIS.

CONCLUSIONS

This study demonstrated that incomplete A-CoW was associated with enhancement grade of the culprit plaque, and incomplete symptomatic side P-CoW was associated with the presence of HT1S of culprit plaque. Furthermore, an irregularity of plaque surface and incomplete symptomatic side P-CoW were associated with AIS.

Neuroimaging of COVID-19

We review the wide variety of common neuroimaging manifestations related to coronavirus disease 2019 (COVID-19) and COVID therapies, grouping the entities by likely pathophysiology, recognizing that the etiology of many entities remains uncertain. Direct viral invasion likely contributes to olfactory bulb abnormalities. COVID meningoencephalitis may represent direct viral infection and/or autoimmune inflammation. Para-infectious inflammation and inflammatory demyelination at the time of infection are likely primary contributors to acute necrotizing encephalopathy, cytotoxic lesion of the corpus callosum, and diffuse white matter abnormality. Later postinfectious inflammation and demyelination may manifest as acute demyelinating encephalomyelitis, Guillain-Barré syndrome, or transverse myelitis. The hallmark vascular inflammation and coagulopathy of COVID-19 may produce acute ischemic infarction, microinfarction contributing to white matter abnormality, space-occupying hemorrhage or microhemorrhage, venous thrombosis, and posterior reversible encephalopathy syndrome. Adverse effects of therapies including zinc, chloroquine/hydroxychloroquine, antivirals, and vaccines, and current evidence regarding "long COVID" is briefly reviewed. Finally, we present a case of bacterial and fungal superinfection related to immune dysregulation from COVID.

Rash, Facial Droop, and Multifocal Intracranial Stenosis Due to Varicella Zoster Virus Vasculitis

Background: This is a case of multifocal intracranial stenosis in a 74 year old male ultimately discovered to be due to Varicella Zoster Virus infection. Purpose: We highlight the importance of a broad differential diagnosis, even when the most likely etiology of intracranial stenosis is atherosclerosis. Our paper reviews the differential diagnosis as well as "red flags" for intracranial vasculopathy. Even though intracranial atherosclerotic disease is the most common cause of vasculopathy, infectious or inflammatory vasculitis should be considered on the differential. Conclusions: Before considering bypass surgery or other invasive neurosurgical procedures, ensure reversible causes of vasculopathy have been ruled out. The presence of cranial neuropathies, rash, and/or elevated inflammatory markers should be red flags for vasculitis in patients presenting with stroke.

Correlation of sLOX-1 Levels and MR Characteristics of Culprit Plaques in Intracranial Arteries with Stroke Recurrence

(1) Background: Symptomatic intracranial artery atherosclerosis (sICAS) is an important cause of acute ischaemic stroke (AIS) and is associated with a high risk of stroke recurrence. High-resolution magnetic resonance vessel wall imaging (HR-MR-VWI) is an effective method for evaluating atherosclerotic plaque characteristics. Soluble lectin-like oxidised low-density lipoprotein receptor-1 (sLOX-1) is closely associated with plaque formation and rupture. We aim to explore the correlation between sLOX-1 levels and culprit plaque characteristics, based on HR-MR-VWI, with stroke recurrence in patients with sICAS. (2) Methods: A total of 199 patients with sICAS underwent HR-MR-VWI between June 2020 and June 2021 in our hospital. The culprit vessel and plaque characteristics were assessed according to HR-MR-VWI, and sLOX-1 levels were measured by ELISA (enzyme linked immunosorbent assay). Outpatient follow-up was performed 3, 6, 9, and 12 months after discharge. (3) Results: sLOX-1 levels were significantly higher in the recurrence group than in the non-recurrence group (p < 0.001). The culprit plaque thickness, degree of stenosis and plaque burden were higher in the recurrence group than in the non-recurrence group (p = 0.003, p = 0.014 and p = 0.010, respectively). The incidence of hyperintensity on T1WI, positive remodelling and significant enhancement (p < 0.001, p = 0.003 and p = 0.027, respectively) was higher in the recurrence group than in the non-recurrence group. Kaplan-Meier curves showed that patients with sLOX-1 levels > 912.19 pg/mL and hyperintensity on T1WI in the culprit plaque had a higher risk of stroke recurrence (both p < 0.001). Multivariate Cox regression analysis showed that sLOX-1 > 912.19 pg/mL (HR = 2.583, 95%CI 1.142, 5.846, p = 0.023) and hyperintensity on T1WI in the culprit plaque (HR = 2.632, 95% CI 1.197, 5.790, p = 0.016) were independent risk factors for stroke recurrence. sLOX-1 levels were significantly associated with the culprit plaque thickness (r = 0.162, p = 0.022), degree of stenosis (r = 0.217, p = 0.002), plaque burden (r = 0.183, p = 0.010), hyperintensity on T1WI (F = 14.501, p < 0.001), positive remodelling (F = 9.602, p < 0.001), and significant enhancement (F = 7.684, p < 0.001) (4) Conclusions: sLOX-1 levels were associated with vulnerability of the culprit plaque and can be used as a supplement to HR-MR-VWI to predict stroke recurrence.

Assessment of the degree of arterial stenosis in intracranial atherosclerosis using 3D high-resolution MRI: comparison with time-of-flight MRA, contrast-enhanced MRA, and DSA

AIM

To compare the accuracy of three-dimensional (3D) high-resolution (HR) magnetic resonance imaging (MRI), time-of-flight magnetic resonance angiography (TOF-MRA), contrast-enhanced magnetic resonance angiography (CE-MRA), and digital subtraction angiography (DSA) in measuring the degree of stenosis in intracranial atherosclerosis.

MATERIALS AND METHODS

All patients with intracranial artery ischaemic events underwent HR-MRI, TOF-MRA, and CE-MRA analysis, and some of these patients underwent DSA examination. The correlation between different methods for measuring the degree of lumen stenosis was analysed. The accuracy of HR-MRI, TOF-MRA, and CE-MRA was evaluated and compared with that of DSA.

RESULTS

A total of 189 arterial stenoses were identified in 93 patients. Of these, 72 patients with 142 arterial stenoses underwent DSA examination. A very strong correlation between HR-MRI and CE-MRA measurements was shown (r=0.839, p<0.0001). The correlation between HR-MRI and TOF-MRA measurements was strong (r=0.720, p<0.0001). A very strong correlation between HR-MRI and DSA measurements was found (r=0.864, p<0.0001), and a similar correlation was observed between CE-MRA, and DSA measurements (r=0.843, p<0.0001). The correlation between TOF-MRA and DSA measurements was strong (r=0.686, p<0.0001). There was substantial agreement between HR-MRI and DSA measurements (K = 0.772) and between CE-MRA, and DSA measurements (K = 0.734) that was slightly higher than the agreement between TOF-MRA and DSA measurements (K = 0.636).

CONCLUSION

HR-MRI can accurately measure stenosis (especially for moderate and severe stenosis) in intracranial atherosclerosis by direct visualisation of the vessel lumen and steno-occlusive plaque.

Association of Preoperative Vascular Wall Imaging Patterns and Surgical Outcomes in Patients With Unruptured Intracranial Saccular Aneurysms

BACKGROUND

MR vascular wall imaging (VWI) may have prognostic value in patients with unruptured intracranial aneurysms (UIAs).

OBJECTIVE

To evaluate the value of VWI as a predictor of surgical outcome in patients with UIAs.

METHODS

This prospective cohort study evaluated surgical outcomes in consecutive patients with UIAs who underwent surgical clipping at a single center. All participants underwent high-resolution VWI and were followed for at least 6 months. The primary clinical outcome was modified Rankin scale (mRS) score 6 months after surgery.

RESULTS

The number of patients in the no wall enhancement, uniform wall enhancement (UWE), and focal wall enhancement (FWE) groups was 37, 145, and 154, respectively. Incidence of postoperative complications was 15.5% in the FWE group, 12.4% in the UWE group, and 5.4% in the no wall enhancement group. The proportion of patients with mRS score >2 at the 6-month follow-up was significantly higher in the FWE group than in the UWE group (14.3% vs 6.9%; P = .0389). In the multivariate analysis, FWE (odds ratio, 2.573; 95% CI 1.001-6.612) and positive proximal artery remodeling (odds ratio, 10.56; 95% CI 2.237-49.83) were independent predictors of mRS score >2 at the 6-month follow-up.

CONCLUSION

Preoperative VWI can improve the surgeon's understanding of aneurysm pathological structure. Type of aneurysmal wall enhancement on VWI is associated with clinical outcome and incidence of salvage anastomosis and surgical complications.

Evaluation of Cerebrovascular Reactivity and Vessel Wall Imaging in Patients With Prior COVID-19: A Prospective Case-Control MRI Study

BACKGROUND. SARS-CoV-2 infection is associated with acute stroke, possibly caused by viral tropism to the vascular endothelium. Whether cerebrovascular endothelial dysfunction and inflammation persist after acute infection is poorly understood. OBJECTIVE. The purposes of this study were to assess the association between prior SARS-CoV-2 infection and cerebrovascular reactivity (CVR) and vessel wall imaging (VWI) abnormalities and to explore the association between CVR impairment and post-COVID neurologic conditions. METHODS. This prospective study included 15 participants with prior SARS-CoV-2 infection (11 women, four men; mean age, 43 years; mean time since infection, 238 days; three with prior critical illness, 12 with prior mild illness; seven with post-COVID neurologic conditions) and 10 control participants who had never had SARS-CoV-2 infection (two women, two men; mean age, 44 years) from July 1, 2021, to February 9, 2022. Participants underwent research MRI that included arterial spin labeling perfusion imaging with acetazolamide stimulus to measure cerebral blood flow (CBF) and calculate CVR. Examinations also included VWI, performed with a contrast-enhanced black-blood 3D T1-weighted sequence. An age- and sex-adjusted linear model was used to assess associations between CVR and prior infection. A t test was used to assess associations between CVR and post-COVID neurologic conditions in participants with previous infection. A difference of proportions test was used to assess associations between VWI abnormalities and infection status. RESULTS. Mean whole-cortex CBF after acetazolamide administration was greater in participants without previous infection than in participants with previous infection (73.8 ± 13.2 [SD] vs 60.5 ± 15.8 mL/100 gm/min; p = .04). Whole-brain CVR was lower in participants with previous infection than those without previous infection (difference, -8.9 mL/100 g/min; p < .001); significantly lower CVR was also observed in participants with previous infection after exclusion of those with prior critical illness. Among participants with previous infection, CVR was lower in those with than those without post-COVID neurologic conditions, although this difference was not significant (16.9 vs 21.0 mL/100 g/min; p = .22). Six of 15 (40%) participants with previous infection versus 1 of 10 (10%) participants without previous infection had at least one VWI abnormality (p = .18). All VWI abnormalities were consistent with atherosclerosis. CONCLUSION. SARS-CoV-2 infection is associated with chronic impairment of CVR. The mechanism is unknown from this study. CLINICAL IMPACT. Future studies are needed to determine the clinical implications of SARS-CoV-2-associated CVR impairment.

Improved Blood Suppression of Motion-Sensitized Driven Equilibrium in High-Resolution Whole-Brain Vessel Wall Imaging: Comparison of Contrast-Enhanced 3D T1-Weighted FSE with Motion-Sensitized Driven Equilibrium and Delay Alternating with Nutation for Tailored Excitation

BACKGROUND AND PURPOSE

High-resolution vessel wall MR imaging is prone to slow-flow artifacts, particularly when gadolinium shortens the T1 relaxation time of blood. This study aimed to determine the optimal preparation pulses for contrast-enhanced high-resolution vessel wall MR imaging.

MATERIALS AND METHODS

Fifty patients who underwent both motion-sensitized driven equilibrium and delay alternating with nutation for tailored excitation (DANTE) preparation pulses with contrast-enhanced 3D-T1-FSE were retrospectively included. Qualitative analysis was performed using a 4-grade visual scoring system for black-blood performance in the small-sized intracranial vessels, overall image quality, severity of artifacts, and the degree of blood suppression in all cortical veins as well as transverse sinuses. Quantitative analysis of the M1 segment of the MCA was also performed.

RESULTS

The qualitative analysis revealed that motion-sensitized driven equilibrium demonstrated a significantly higher black-blood score than DANTE in contrast-enhanced 3D-T1-FSE of the A3 segment (3.90 versus 3.58, P < .001); M3 (3.72 versus 3.26, P = .004); P2 to P3 (3.86 versus 3.64, P = .017); the internal cerebral vein (3.72 versus 2.32, P < .001); and overall cortical veins (3.30 versus 2.74, P < .001); and transverse sinuses (2.82 versus 2.38, P < .001). SNR_lumen, contrast-to noise ratio_wall-lumen, and SNR_wall in the M1 vessel were not significantly different between the 2 preparation pulses (all, P > .05).

CONCLUSIONS

Motion-sensitized driven equilibrium demonstrated improved blood suppression on contrast-enhanced 3D-T1-FSE in the small intracranial arteries and veins compared with DANTE. Motion-sensitized driven equilibrium is a useful preparation pulse for high-resolution vessel wall MR imaging to decrease venous contamination and suppress slow-flow artifacts when using contrast enhancement.

Intimal hyperplasia detection after aneurysm treatment by flow diversion using magnetic resonance vessel wall imaging

In-stent caliber reduction due to neo-intimal hyperplasia (NIH) is an underestimated event that may follow flow diverter stent (FDS) implantation. Although mostly asymptomatic, this vascular reaction is a well-known risk factor for delayed ischemic strokes. Here we report on the contribution of magnetic resonance vessel wall imaging (MR-VWI), performed on a 1.5 T scanner, to detect in-stent stenosis and mural inflammation in a 40-year-old woman with cerebral aneurysm previously treated with FDS and presenting with motor disturbances on follow-up. Digital subtraction angiography and cone-beam CT confirmed 1.5 T MRVWI findings, highlighting the potential value of this non-invasive imaging technique in investigating and detecting NIH.

Spontaneous internal carotid artery dissection in a child diagnosed by high resolution vessel wall MRI

Craniocervical dissection is one of the most common causes of stroke in children. Although the most common cause of dissection is trauma, spontaneous dissections in which no cause can be revealed may also occur. The diagnosis of this type of dissection in children can be challenging with the preferred non-invasive imaging methods (MRA, CTA). Intracranial vessel wall imaging is a promising novel method for identifying specific signs of dissection. We report an 11-year-old girl with spontaneous ICA dissection, whose diagnosis was confirmed by an MRI of the intracranial vessel wall. Vessel wall imaging has contributed substantially to the diagnosis and follow-up of this case.

Neuroimaging in Pediatric Stroke

Pediatric stroke is unfortunately not a rare condition. It is associated with severe disability and mortality because of the complexity of potential clinical manifestations, and the resulting delay in seeking care and in diagnosis. Neuroimaging plays an important role in the multidisciplinary response for pediatric stroke patients. The rapid development of adult endovascular thrombectomy has created a new momentum in health professionals caring for pediatric stroke patients. Neuroimaging is critical to make decisions of identifying appropriate candidates for thrombectomy. This review article will review current neuroimaging techniques, imaging work-up strategies and special considerations in pediatric stroke. For resources limited areas, recommendation of substitute imaging approaches will be provided. Finally, promising new techniques and hypothesis-driven research protocols will be discussed.

Pediatric Moyamoya Biomarkers: Narrowing the Knowledge Gap

Moyamoya is a progressive cerebrovascular disorder that leads to stenosis of the arteries in the distal internal carotid, proximal middle cerebral and proximal anterior cerebral arteries of the circle of Willis. Typically a network of collaterals form to bypass the stenosis and maintain cerebral blood flow. As moyamoya progresses it affects the anterior circulation more commonly than posterior circulation, and cerebral blood flow becomes increasingly reliant on external carotid supply. Children with moyamoya are at increased risk for ischemic symptoms including stroke and transient ischemic attacks (TIA). In addition, cognitive decline may occur over time, even in the absence of clinical stroke. Standard of care for stroke prevention in children with symptomatic moyamoya is revascularization surgery. Treatment of children with asymptomatic moyamoya with revascularization surgery however remains more controversial. Therefore, biomarkers are needed to assist with not only diagnosis but also with determining ischemic risk and identifying best surgical candidates. In this review we will discuss the current knowledge as well as gaps in research in relation to pediatric moyamoya biomarkers including neurologic presentation, cognitive, neuroimaging, genetic and biologic biomarkers of disease severity and ischemic risk.

Reversible cerebral vasoconstriction syndrome: review of neuroimaging findings

Reversible cerebral vasoconstriction syndrome (RCVS) is a group of disorders characterized by segmental narrowing and dilatation of medium-to-large cerebral arteries, clinically presenting with recurrent episodes of sudden-onset thunderclap headaches, with or without focal neurological deficits. Cerebral vasoconstriction is typically reversible, with spontaneous resolution within 3 months. Although the syndrome has generally a benign course, patients with neurological deficits may experience worse outcome. The main imaging finding is segmental constriction of intracranial arteries, which can be associated with subarachnoid hemorrhage and/or ischemic foci. Other possible findings are intracranial hemorrhage, subdural bleeding and cerebral edema. The latter may have a pattern which can resemble that of posterior reversible encephalopathy syndrome, a condition that can overlap with RCVS. New imaging techniques, such as vessel wall imaging and arterial spin labeling, are proving useful in RCVS and are giving new insights into the pathophysiology of this condition. In this paper, we aim to review neuroimaging findings of RCVS.

The Utility of Vessel Wall Imaging in the Postulation of Acute Ischemic Stroke With Spontaneous Recanalization Pathophysiology

Recent advances in technology, particularly in the field of magnetic resonance imaging, have brought forth new sequences, including vessel wall imaging (VWI). Traditionally, the workup for intracranial vascular pathology has always turned to luminal imaging using computed tomography angiography, magnetic resonance angiography, or digital subtraction angiography. Since its introduction, VWI has enabled researchers and practicing clinicians to better understand disease processes and manage patients to the best standard of care possible. Spontaneous recanalization in acute ischemic stroke (AIS) is a known but understudied phenomenon. Available literature has looked at this phenomenon and postulated the occurrence based on conventional cross-sectional imaging and angiography; however, objective evidence pointing to the occurrence of this phenomenon is scarce. We would like to share our experience using VWI in a patient who was clinically suspected to have a middle cerebral artery syndrome at onset, with resolution of the symptoms 3 hours after initial presentation. VWI showed vessel wall enhancement at the suspected vessel involved, with evidence of acute infarcts at the vascular territory supplied. A presumptive diagnosis of AIS with spontaneous recanalization was made. Our experience could potentially aid in the understanding of spontaneous recanalization in patients with AIS, particularly in the postulation of the pathophysiology.