diagnosis and imaging

Kristina Shkirkova, BSc

Wyss A, Dawson J, Arba F, Wardlaw JM, Dickie DA, on behalf of the VISTA-Prevention Collaborators. “Combining Neurovascular and Neurodegenerative Magnetic Resonance Imaging Measures in Stroke.” Stroke. 2019; 50:1136-1139.

To characterize age and stroke-related tissue damage, the total small vessel disease score and the brain health index have recently been developed for clinical use. The total small vessel disease score combines presence of lacunes, microbleeds, and moderate to severe white matter hyperintensities (WMH) by visual scoring based on clinical imaging. The brain health index uses automatic processing of MRI scans to quantify visible injury from small vessel disease and brain atrophy. However, the total small vessel disease score is prone to granularity and measurement limitations, whereas the brain health index requires high-resolution T1, T2, T2 gradient echo, and fluid attenuated inversion recovery scans, which are not often available in routine clinical imaging.

The study by Wyss et al. argues that individual markers of cerebral small vessel disease and brain atrophy have limited potential to explain high proportion of variance in neurovascular and neurodegenerative disease. The authors propose to combine markers of white matter hyperintensity and cerebral atrophy, represented by cerebrospinal fluid (CSF) volume, into a single measure capable of more accurate predictions of cognitive impairment.

Alejandro Fuerte, MD
@DrFuerte1

Fullerton H, Stence N, Hills N, Jiang B, Amlie-Lefond C, Bernard T, et al. Focal Cerebral Arteriopathy of Childhood: Novel Severity Score and Natural History. Stroke. 2018

Focal cerebral arteriopathy (FCA) of childhood is an acute disease causing unilateral stenosis of the cerebral arteries. It appears to be caused by an inflammatory process, and corticosteroids are used in its treatment in the absence of clinical trial data. Because it is one of the most common causes of arterial ischemic stroke (AIS) in healthy children and it increases the risk of recurrent stroke, a Delphi consensus identified this issue as the highest priority for a clinical trial in the field of childhood stroke.

The main goal of Fullerton et al. was to develop a severity score for this disease (Focal Arteriopathy Childhood Severity Score; FCASS). For this they used data from the VIPS study (Vascular Effects of Infection in Pediatric Stroke), a large, international, prospective cohort study that enrolled 355 children (29 days to 18 years of age) with AIS and collected clinical, imaging data and serum samples.

Kara Jo Swafford, MD

Berndt M, Friedrich B, Maegerlein C, Moench S, Hedderich D, Lehm M, et al. Thrombus Permeability in Admission Computed Tomographic Imaging Indicates Stroke Pathogenesis Based on Thrombus Histology. Stroke. 2018

Mechanical thrombectomy for treatment of an acute ischemic stroke caused by a large vessel occlusion provides the possibility of histological study of the thrombus, which is composed of fibrin, platelets, red blood cells and white blood cells. Higher fibrin content is associated with a cardiogenic origin. Clot permeability or perviousness depends on its constituents and can be assessed by the quantity of contrast present within the thrombus on CT angiography (CTA).

Berndt et al. assessed the correlation between the histological composition of clot retrieved by mechanical thrombectomy and the perviousness of the clot on CTA. They hypothesized that clot perviousness could assist in determining the stroke pathogenesis, guiding clinical decisions related to secondary stroke prevention. They found that permeable thrombi consist of mainly fibrin-platelet conglomerations and fewer red blood cells and were associated with cardioembolic stroke. Conversely, they found that lower perviousness was associated with thrombi containing mostly red blood cells and were most likely of noncardioembolic origin.

Alexis N. Simpkins, MD, PhD

Puig J, Blasco G, Alberich-Bayarri A, Schlaug G, Deco G, Biarnes C, et al. Resting-State Functional Connectivity Magnetic Resonance Imaging and Outcome After Acute Stroke. Stroke. 2018

Many ischemic stroke patients will have residual disability from their stroke even if they receive thrombolysis or endovascular therapy. In fact, stroke is and is projected to continue to be one of the leading causes of long-term disability in adults. Identifying tools that can be used to accurately predict expected stroke recovery can change the way the patient is medically managed and can be used as an outcome measure in clinical trials. Changes in NIHSS, infarct volume, and stroke lesion have been shown to predict early neurologic outcome, but there are still limitations with each of these predictors. As a result, there are continued efforts to provide more sensitive and specific predictive models. Here, the authors assessed whether resting state-functional MRI (rs-fMRI) is associated with projected neurologic outcome at 90 days and can be combined with other frequently used predictors to improve accuracy. The selection of rs-fMRI was supported by previous studies that demonstrated an association between resting state and task-oriented functional connectivity and previous reports of the role of interhemispheric connectivity in stroke recovery.

Houman Khosravani, MD, PhD

Vagal A, Aviv R, Sucharew H, Reddy M, Hou Q, Michel P, et al. Collateral Clock Is More Important Than Time Clock for Tissue Fate: A Natural History Study of Acute Ischemic Strokes. Stroke. 2018

“We hold these truths to be self-evident” is stated in the Declaration of Independence, and some say that with the passage of time, all becomes self-evident. Thus, what is the impact of time, and what is the truth behind the function and abundance of collateral circulation? These answers are critical to the late-window management of acute stroke. The topic will be one that keeps on giving, and an important contribution to this topic comes from a recent paper by Vagal et al.

In both early and extended time-windows brought about by DAWN and DEFUSE 3, the presence and functional capacity of robust collaterals has become uniquely important. The ischemic penumbra can persist for prolonged periods of time (up to 48 hrs), and its survival rests in part with the collateral circulation. The ability to assess this important aspect of tissue health is key in the evolution of thinking that is taking place: a move from time-window to tissue-health window. At the forefront of this assessment is perfusion imaging — in the case of this research, using CT perfusion. Understanding how time affects the natural history of the penumbra stands to inform assessment and decision-making in the era of EVT for patients within 24 hrs of symptom onset. Vagal et al. explore time from stroke onset and infarct growth in untreated acute ischemic stroke patients within this time window with the purpose of understanding how collaterals affect this evolution. However, it is important to note that data in this study were collected in the era of TPA first up to 3 hrs, then up to 4.5 hrs, and IA-TPA up to six hours (spanning 2003-2011) — thus, prior to the current EVT era. Nonetheless, patients who met inclusion criteria did not receive any therapy allowing for assessment of the penumbra’s natural history.