Nonstenotic Carotid Plaques and Embolic Stroke of Undetermined Source: A Multimodality Review.

Symptomatic nonstenotic carotid artery disease has been increasingly recognized as a thromboembolic source in patients who would otherwise be classified as having embolic stroke of undetermined source. Evidence suggests that certain plaque features seen on sonography, CT, and MR imaging in nonstenotic carotid artery disease may predispose to recurrent stroke in patients with embolic stroke of undetermined source. We performed a focused literature review to further study plaque features in the context of embolic stroke of undetermined source and to determine which plaque features may be associated with ipsilateral ischemic events in such patients. Plaque thickness as seen on both ultrasound and CT appears to have a consistent association with ipsilateral stroke in patients with embolic stroke of undetermined source across multiple studies. Intraplaque hemorrhage as seen on MR imaging is now understood to have a strong association with ipsilateral stroke in patients with embolic stroke of undetermined source. Continued study of various plaque features as seen on different modalities is warranted to uncover other potential associations.

Radiology-Pathology Correlations of Intracranial Clots: Current Theories, Clinical Applications, and Future Directions.

In recent years, there has been substantial progression in the field of stroke clot/thrombus imaging. Thrombus imaging aims to deduce the histologic composition of the clot through evaluation of various imaging characteristics. If the histology of a thrombus can be reliably determined by noninvasive imaging methods, critical information may be extrapolated about its expected response to treatment and about the patient's clinical outcome. Crucially, as we move into an era of stroke therapy individualization, determination of the histologic composition of a clot may be able to guide precise and targeted therapeutic effort. Most radiologists, however, remain largely unfamiliar with the topic of clot imaging. This article will review the current literature regarding clot imaging, including its histologic backdrop, the correlation of images with cellular components and treatment responsiveness, and future expectations.

Carotid Intraplaque Hemorrhage and Stenosis: At What Stage of Plaque Progression Does Intraplaque Hemorrhage Occur, and When is It Most Likely to Be Associated with Symptoms?

BACKGROUND AND PURPOSE: The relationship between carotid intraplaque hemorrhage and luminal stenosis severity is not well-established. We sought to determine whether intraplaque hemorrhage is related to carotid stenosis and at what degree of stenosis intraplaque hemorrhage most likely contributes to ischemic symptoms. MATERIALS AND METHODS: Consecutive patients who underwent MR carotid plaque imaging with MPRAGE sequences to identify intraplaque hemorrhage were retrospectively reviewed. Degrees of stenoses were categorized as minimal (<30%), moderate (30%-69%), and severe (>70%). Arteries were categorized into 2 groups: symptomatic (ipsilateral to a cerebral ischemic event) and asymptomatic (from a patient without an ischemic event). Multiple regression analyses were used to determine independent associations between the degree of stenosis and intraplaque hemorrhage and the presence of intraplaque hemorrhage with symptoms among categories of stenosis. RESULTS: We included 449 patients with 449 carotid arteries: Two hundred twenty-five (50.1%) were symptomatic, and 224 (49.9%) were asymptomatic. An increasing degree of stenosis was independently associated with the presence of intraplaque hemorrhage (OR = 1.02; 95% confidence interval, 1.01-1.03). Intraplaque hemorrhage was independently associated with ischemic events in arteries with <30% stenosis (OR = 5.68; 95% CI, 1.49-21.69). No such association was observed in arteries with >30% stenosis. Of symptomatic arteries with minimal stenosis, 8.7% had intraplaque hemorrhage versus 1.7% of asymptomatic arteries (P = .02). No differences in intraplaque hemorrhage prevalence were found between symptomatic and asymptomatic groups with moderate (P = .18) and severe stenoses (P = .99). CONCLUSIONS: The presence of intraplaque hemorrhage on high-resolution plaque imaging is likely most useful in identifying symptomatic plaques in cases of minimal stenosis.

Variations of Intracranial Dural Venous Sinus Diameters from Birth to 20 Years of Age: An MRV-Based Study.

BACKGROUND AND PURPOSE: The role of the dural venous sinus system in cerebrovascular pathology and the understanding of normal developmental patterns and sizes of the dural venous sinus system continue to expand. The purpose of this study was to review MR venograms to elucidate developmental patterns and diameters of the major dural venous sinuses from 0 to 20 years of age. MATERIALS AND METHODS: All available MR venograms of patients 0-20 years of age who presented to our institution were retrospectively reviewed. Patient age at the time of image acquisition was noted, and measurements were taken of the diameters of the major dural venous sinuses. The presence of embryonic sinuses including the persistent falcine sinus and the occipital sinus was noted. Dominance patterns of the transverse sinus system were determined. Mean diameters of each sinus were plotted as a function of age. The prevalence of persistent prenatal sinuses and transverse sinus-dominance patterns was compared across ages. RESULTS: A total of 429 MR venograms from 429 patients were reviewed. All dural venous sinuses demonstrated a maximal growth rate from 0 to 7 years of age and reached maximal diameters around 5-10 years of age. The prevalence of falcine sinuses and occipital sinuses trended downward across increasing age categories (P = .09 and, <.0001, respectively). CONCLUSIONS: Dural venous sinuses demonstrate maximal growth between 0 and 7 years of age and reach adult size around 5-10 years of age. Involution of the prenatal sinuses continues to take place after birth into childhood but is largely absent in early adulthood.

Lack of Baseline Intracranial Aneurysm Wall Enhancement Predicts Future Stability: A Systematic Review and Meta-Analysis of Longitudinal Studies.

BACKGROUND: The utility of vessel wall MR imaging in identifying unstable intracranial aneurysms has been suggested but remains controversial. PURPOSE: Our aim was to provide further insight into the potential relationship between aneurysm wall enhancement on initial vessel wall imaging and aneurysm instability at follow-up. DATA SOURCES: Our sources were PubMed, Scopus, the Web of Science, and the Cochrane Central Register of Controlled Trials. STUDY SELECTION: We searched for English language studies that reported the presence of vessel wall enhancement of unruptured intracranial aneurysms on baseline vessel wall imaging studies with longitudinal follow-up of aneurysm status. DATA ANALYSIS: Aneurysms were grouped into "stable" and "unstable" groups at follow-up on the basis of growth, symptomatic manifestation, or rupture. The association of each group with aneurysm wall enhancement on initial vessel wall imaging was determined. DATA SYNTHESIS: Three studies constituting 407 aneurysms were included. Aneurysms with wall enhancement were at higher risk of being unstable at follow-up (risk ratio = 3.6; 95% confidence interval, 1.7-7.5). The sensitivity of aneurysm wall enhancement on vessel wall imaging was 74.3% (95% CI, 56.7%-87.5%), specificity was 58.3% (95% CI, 53.1%-63.4%), positive predictive value was 14.4% (95% CI, 11.8%-17.4%), negative predictive value was 96.0% (95% CI, 93.2%-97.7%), and the overall accuracy of the test was 59.7% (95% CI, 54.8%-64.5%). LIMITATIONS: Only 3 studies were identified for inclusion in this analysis. More longitudinal studies of vessel wall imaging and aneurysm progression are needed. CONCLUSIONS: The lack of wall enhancement may be a predictor of aneurysm stability. The utility of vessel wall imaging in detecting unstable aneurysms requires more data.