Current Clinical Applications of Intracranial Vessel Wall MR 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.

MRI in the Evaluation of Cryptogenic Stroke and Embolic Stroke of Undetermined Source

Cryptogenic stroke refers to a stroke of undetermined etiology. It accounts for approximately one-fifth of ischemic strokes and has a higher prevalence in younger patients. Embolic stroke of undetermined source (ESUS) refers to a subgroup of patients with nonlacunar cryptogenic strokes in whom embolism is the suspected stroke mechanism. Under the classifications of cryptogenic stroke or ESUS, there is wide heterogeneity in possible stroke mechanisms. In the absence of a confirmed stroke etiology, there is no established treatment for secondary prevention of stroke in patients experiencing cryptogenic stroke or ESUS, despite several clinical trials, leaving physicians with a clinical dilemma. Both conventional and advanced MRI techniques are available in clinical practice to identify differentiating features and stroke patterns and to determine or infer the underlying etiologic cause, such as atherosclerotic plaques and cardiogenic or paradoxical embolism due to occult pelvic venous thrombi. The aim of this review is to highlight the diagnostic utility of various MRI techniques in patients with cryptogenic stroke or ESUS. Future trends in technological advancement for promoting the adoption of MRI in such a special clinical application are also discussed.

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.

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.

Non-Aneurysmal Perimesencephalic Subarachnoid Hemorrhage: A Literature Review

Spontaneous non-aneurysmal subarachnoid haemorrhage (NAPMSAH) (addressing point 1) is a relatively rare occurrence in clinical settings as it is rarely misdiagnosed and usually involves a significantly better prognosis than the classical aneurysmal pattern. We hereby focused on a comprehensive analysis of this distinct pathological entity with the purpose of analysing possible pathophysiological entities, outcomes and treatment options involving this diagnosis with a focus on demographical, epidemiological and clinical data. The clinical setting includes focal neurological signs related to the anatomical structures, while computer tomography followed by tomographic angiography are the most common diagnosis tools, with a typical hyperdense lesion involving the midbrain, fourth ventricle and subthalamic areas without an angiographic correspondent, such as an aneurysmal pathology. Further investigations can also be used to highlight this diagnosis, such as interventional angiography or magnetic resonance imaging. Given the rarity of this condition and its relatively better prognosis, treatment options usually remain conservative. In the present review, the main characteristics of NAPMSAH are discussed.

Ischemic stroke caused by spontaneous anterior circulation intracranial arterial dissections: patient series

BACKGROUND

Intracranial arterial dissections (IADs) are classically associated with the vertebrobasilar system, yet are a devastating cause of ischemic stroke within the anterior circulation. Current literature regarding the surgical management of anterior circulation IAD is lacking. As a result, data on 9 patients presenting with ischemic stroke due to spontaneous anterior circulation IAD between 2019 and 2021 were collected in a retrospective manner. Symptoms, diagnostic modalities, treatment, and outcomes are presented for each case. Patients who underwent endovascular procedures had 10-minute follow-up angiography performed to identify signs of reocclusion, which prompted initiation of glycoprotein IIb/IIIa therapy and stent placement.

OBSERVATIONS

Seven patients underwent emergent endovascular intervention (stenting: n = 5; thrombectomy alone: n = 2). The remaining 2 were managed medically. Two patients developed progressive flow limiting stenosis requiring further intervention, 2 developed asymptomatic progressive stenosis/occlusion with robust collateral formation and the remainder have patent vasculature upon follow up imaging at 6 to 12 months. Seven patients had a modified Rankin Scale score of 1 or less at the 3-month follow-up.

LESSONS

IAD is a devastating yet rare cause of anterior circulation ischemic stroke. The treatment algorithm proposed resulted in positive clinical and angiographic outcomes warranting future consideration and study in the emergent management of spontaneous anterior circulation IAD.

Application and interpretation of vessel wall magnetic resonance imaging for intracranial atherosclerosis: a narrative review

Background and Objective

Atherosclerosis is a systemic disease that occurs in the arteries, and it is the most important causative factor of ischemic stroke. Vessel wall magnetic resonance imaging (VWMRI) is one of the best non-invasive methods for displaying the vascular features of intracranial atherosclerosis. The main clinical applications of this technique include the exploration of the pathogenesis of intracranial atherosclerotic lesions, follow-up monitoring, and treatment prognosis judgment. As the demand for intracranial VWMRI increases in clinical practice, radiologists should be aware of the selection of imaging parameters and how they affect image quality, clinical indications, evaluation methods, and limitations in interpreting these images. Therefore, this review focused on describing how to perform and interpret VWMRI of intracranial atherosclerotic lesions.

Methods

We searched the studies on the application of VWMRI in the PubMed database from January 1, 2000 to March 31, 2022, and focused on the analysis of related studies on VWMRI in atherosclerotic lesions, including technical application, expert consensus, imaging characteristics, and the clinical significance of intracranial atherosclerotic lesions.

Key Content and Findings

We reviewed and summarized recent advances in the clinical application of VWMRI in atherosclerotic diseases. Currently accepted principles and expert consensus recommendations for intracranial VWMRI include high spatial resolution, multiplanar two and three-dimensional imaging, multiple tissue-weighted sequences, and blood and cerebrospinal fluid suppression. Understanding the characteristics of VWMRI of normal intracranial arteries is the basis for interpreting VWMRI of atherosclerotic lesions. Evaluating VWMRI imaging features of intracranial atherosclerotic lesions includes plaque morphological and enhancement characteristics. The evaluation of atherosclerotic plaque stability is the highlight of VWMRI.

Conclusions

VWMRI has a wide range of clinical applications and can address important clinical questions and provide critical information for treatment decisions. VWMRI plays a key role in the comprehensive evaluation and prevention of intracranial atherosclerosis. However, intracranial VWMRI is still unable to obtain in vivo plaque pathological specimens for imaging—pathological comparison is the most significant limitation of this technique. Further technical improvements are expected to reduce acquisition time and may ultimately contribute to a better understanding of the underlying pathology of lesions on VWMRI.

Takayasu arteritis

PURPOSE OF REVIEW

The purpose of this review is to summarize the recent advances in Takayasu arteritis (TAK), mainly focusing on pathogenesis, imaging modalities, and management.

RECENT FINDINGS

Three novel clusters based on angiographic findings were identified in the Indian cohort and replicated in the North American cohorts. Different new imaging modalities have been tried in the assessment of arterial inflammation with promising results. There is more evidence on the long-term use of tocilizumab, but relapses are common. In light of the recent findings on the pathogenesis of TAK, Janus kinase inhibitors seem to be promising.

SUMMARY

Improvement in imaging modalities and in our understanding of the disease pathogenesis will allow us to better assess the disease activity and identify effective therapeutic agents.