CT and MRI Early Vessel Signs Reflect Clot Composition in Acute Stroke

Abstract

Background and Purpose To provide the first correlative study of the hyperdense MCA sign (HMCAS) and gradient-echo (GRE) MRI blooming artifact (BA) with pathology of retrieved thrombi in acute ischemic stroke. Methods Noncontrast CT and GRE MRI studies prior to mechanical thrombectomy in 50 consecutive cases of acute MCA ischemic stroke were reviewed, blinded to clinical and pathology data. Occlusions retrieved by thrombectomy underwent histopathologic analysis, including automated quantitative and qualitative rating of proportion composed of red blood cells (RBC), white blood cells (WBC), and fibrin on microscopy of sectioned thrombi. Results Among 50 patients, mean age was 66 years and 48% were female. Mean (SD) proportion was 61% (±21) fibrin, 34% (±21) RBC, and 4% (±2) WBC. Of retrieved clots, 22 (44%) were fibrin-dominant, 13 (26%) RBC-dominant and 15 (30%) mixed. HMCAS was identified in 10/20 MCA stroke cases with CT, with mean Hounsfield Unit (HU) density of 61 (SD±8). BA occurred in 17/32 with GRE MRI. HMCAS was more commonly seen with RBC-dominant and mixed than fibrin-dominant clots (100% vs. 67% vs. 20%, p=0.016). Mean percent RBC composition was higher in clots associated with HMCAS (47% vs. 22%, p=0.016). BA was more common in RBC-dominant and mixed clots compared to fibrin-dominant clots (100% vs. 63% vs. 25%, p=0.002). Mean percent RBC was greater with BA (42% vs. 23%, p=0.011). Conclusions CT HMCAS and GRE MRI BA reflect pathology of occlusive thrombus. RBC content determines appearance of HMCAS and BA, whereas absence of HMCAS or BA may indicate fibrin-predominant occlusive thrombi.

Inflammatory mediator expression within retrieved clots in acute ischemic stroke

“…Mechanical thrombectomy is notable because it allows for histologic evaluation of clots retrieved from human intracranial arteries, potentially broadening our insight into stroke etiology as well as our understanding of clot appearance on imaging studies. Several recent studies involving the histologic analysis of intracranial clots retrieved by mechanical thrombectomy in acute stroke patients have focused on blood cell composition in clots using either hematoxylin and eosin or immunohistochemical staining 2, 3, 4, 5, 6, 7…”

Microstructural evaluation by confocal and electron microscopy in thrombi developed in central venous catheters

“…Unlike thrombi with homogeneous structure composed predominantly of erythrocytes and sparse regions of fibrin and platelets described from in vitro or laboratory animal studies (4,(15)(16) , the thrombus evaluated in the present study had a heterogeneous structure. Large amounts of fibrin layers and platelets were observed near the vessel wall, and fibrin layers with erythrocytes were present in higher quantity in the center of the thrombus (Figures 4 and 5).…”

“…Analysis by Confocal Laser Scanning Microscopy is an optical technique based on fluorescence induction by an absorption photon, which demonstrates high potential in characterizing biological samples in the hydrated state without the need to section them (14) . It has recently been applied to studies of in vivo thrombosis formation and aided thrombolytic treatment in cannulated rats (14)(15)(16) . Considering the three-dimensional microscopic architecture of a thrombus, Scanning Electron Microscopy (SEM) is one of the elective techniques for morphological characterization (13) .…”

Proximal flow to middle cerebral artery is associated with higher thrombus density in terminal internal carotid artery occlusion

“…Proximal collateral perfusion could attenuate the hypercoaguable state, and remove hypodense and less dissolvable components within the thrombus 12. In turn, this might support the endo‐ and exogenous fibrinolytic action by improved access of soluble factors to the gaps among adjacent platelets, fibrin filaments, and red blood cells 13. Whether the increased detection of leptomenigneal collaterals in I‐type occlusion is a consequence of proximal MCA collaterals, thrombus perviousness, or an independent process can only be answered with the analysis of larger cohorts.…”