diagnosis and imaging

Mona Al Banna, MB BCh, Msc(Res)
@DrMonaAlBanna

van Dam-Nolen DHK, van Egmond NCM, Dilba K, Nies K, van der Kolk AG, Liem MI, Kooi ME, Hendrikse J, Nederkoorn PJ, Koodstaal PJ, et al. Sex Differences in Plaque Composition and Morphology Among Symptomatic Patients With Mild-to-Moderate Carotid Artery Stenosis. Stroke. 2022.

Data regarding outcome differences in carotid revascularization between males and females has been mixed. The authors of this study set out to explore whether carotid plaque composition and morphology differed between male and female stroke patients using an imaging-based approach whilst taking into account degree of plaque burden. The plaque characteristics that were evaluated included intra-plaque hemorrhage, lipid rich necrotic core, calcifications, thin or ruptured fibrous cap, plaque ulcerations and total plaque volume. The authors also explored combinations of plaque characteristics to evaluate the relationship between multiple vulnerable plaque phenotypes. Plaque characteristics were assessed with CTA and dedicated vessel wall MRI.

Tolga D. Dittrich, MD

Wouters A, Robben D, Christensen S, Marquering HA, Roos YBWEM, van Oostenbrugge RJ, van Zwam WH, Dippel DWJ, Majoie CBLM, Schonewille WJ, et al. Prediction of Stroke Infarct Growth Rates by Baseline Perfusion Imaging. Stroke. 2021.

For the acute treatment of ischemic stroke with endovascular therapy (EVT), the time between symptom onset and therapy initiation is considered crucial so far. However, the trend has shifted in recent years from rigid time windows to more individualized, advanced imaging-based, patient selection for EVT.

CT-based perfusion imaging (CTP) has gained importance in identifying individuals with potentially salvageable brain tissue. Automated perfusion assessments using specialized software (e.g., RAPID) are frequently employed in clinical practice to calculate mismatch volume. For the analysis, two key parameters are defined: the relative cerebral blood flow (rCBF) below 30% as a reflection of the ischemic core volume and the delay to the maximum of the residue function (Tmax) of more than 6 seconds, which defines critically hypoperfused brain tissue. The final infarct volume often corresponds with the ischemic core volume determined at baseline in cases of successful reperfusion. In patients without reperfusion, the size of the hypoperfused brain tissue can be used to predict the final infarct size. However, accurate prediction of final infarct size, especially as a function of reperfusion status, is not possible using these conventional CTP analyses as they only represent snapshots at the time of examination.

Vignan Yogendrakumar, MD, MSc
@VYogendrakumar

Kappelhof M, Tolhuisen ML, Treurniet KM, Dutra BG, Alves H, Zhang G, Brown S, Muir KW, Dávalos A, Roos YBWEM, et al. Endovascular Treatment Effect Diminishes With Increasing Thrombus Perviousness: Pooled Data From 7 Trials on Acute Ischemic Stroke. Stroke. 2021.

In the context of large vessel occlusion stroke, a growing number of advanced imaging studies are showing us that no two occlusions are alike. The imaging features of a thrombus can provide critical information that can inform us about the effectiveness of a given therapy. For example, the INTERRSeCT study published in 2018 showed that distal thrombus location and increased thrombus permeability were associated with increased rates of spontaneous recanalization with IV thrombolysis.

In this study, Kappelhof and colleagues utilize data from the HERMES dataset to assess thrombus permeability and determine its effect on clinical outcomes in patients who received EVT compared to those who received thrombolysis alone. The authors refer to permeability as “thrombus perviousness” and measured this by co-registering non-contrast CT (NCCT) and single-phase CTA images together and measuring the attenuation increase between NCCT and CTA images (Figure 2). The primary clinical outcome of the study was an ordinal analysis of the mRS.

Elena Zapata-Arriaza, MD PhD
@ElenaZaps

Thirugnanachandran T, Beare R, Mitchell M, Wong C, Vuong J, Singhal S, Slater LA, Hilton J, Sinnott M, Srikanth V, et al. Anterior Cerebral Artery Stroke: Role of Collateral Systems on Infarct Topography. Stroke. 2021.

Anterior cerebral artery (ACA) stroke is less frequent when compared with middle cerebral artery (MCA) occlusion, and consequently, mechanical thrombectomies, perfusion studies, pial collateral system or clinical consequences based on the topography of the lesion are less known. With the aim of evaluating the role of the circle of Willis (CoW) and leptomeningeal anastomoses (LA) in modifying regional variation in infarct topography following occlusion of the anterior cerebral artery and its branches, Thirugnanachandran and colleagues employed voxel-based imaging in conjunction with computer model of cerebral circulation to understand the temporal and spatial evolution of the topography of ACA stroke following vessel occlusion. The experiments included occlusion of successive branches of the anterior cerebral artery while the configurations of the CoW were varied.

Tolga Daniel Dittrich, MD

García-Tornel Á, Campos D, Rubiera M, Boned S, Olivé-Gadea M, Requena M, Ciolli L, Muchada M, Pagola J, Rodriguez-Luna D, et al. Ischemic Core Overestimation on Computed Tomography Perfusion. Stroke. 2021.

Computed tomography perfusion (CTP) has become widely accepted as the imaging modality for the estimation of the infarct core and subsequent selection for endovascular treatment (EVT) in ischemic stroke due to large vessel occlusion (LVO), especially in the late time window. The radiological correlate for the core in CTP is usually the volume of tissue with a (compared with the contralateral hemisphere) reduction in cerebral blood flow (CBF) <30%. Overestimation of the core in CTP is thought to be time-dependent and may be a concern, especially with rapid imaging after symptom onset and fast reperfusion after imaging.

García-Tornel et al. addressed the question of the influence of time and collateral status on ischemic core overestimation. They retrospectively evaluated patients with anterior circulation LVO strokes with successful reperfusion after EVT. The core was considered to be the tissue with CBF <30% in CTP. Collateral status was assessed by the hypoperfusion intensity ratio (time to maximum of tissue residue function >6 seconds/time to maximum of tissue residue function >10 seconds). The reference for the final infarct volume was the non-contrast CT after 24 to 48 hours.