# Thrombus Composition in Cerebral Venous Thrombosis

## TL;DR

This study compares the composition of blood clots in cerebral venous thrombosis and stroke, finding that venous clots are larger, contain more red blood cells, and less fibrin, which correlates with CT scan density.

## Contribution

The study is the first to compare cerebral venous thrombosis thrombi with stroke thrombi using histological and CT density analysis.

## Key findings

- CVT thrombi are larger and have lower fibrin content compared to AIS thrombi.
- High red blood cell content and low fibrin correlate with CT density measurements in CVT.
- CVT thrombi show signs of early organization and variable histological features.

## Abstract

Background and Aims: Histological analysis of thrombi can enhance the understanding of pathophysiology. We aimed to analyze EVT-retrieved thrombi in cerebral venous thrombosis (CVT), compare them with acute ischemic stroke (AIS) thrombi, and correlate their composition with CT density.

Methods: Retrospective case-series, including five CVT and 10 AIS cases treated with EVT. Thrombus sections were stained with hematoxylin and eosin; Picro Mallory for RBCs, fibrin, and collagen; and Prussian Blue for iron plus immunohistochemical staining with anti-CD61 (platelets), anti-MPO (neutrophils), anti-CD3 (T-cells), anti-CD20 (B-cells), anti-CD34 (endothelial cells), anti-CD68 (macrophages), and anti-citH3 (NETs). Thrombus components were quantified (Orbit) and expressed as a percentage of total area. The CVT-thrombus relative density (rHU) was calculated as HU thrombus/HU contralateral.

Results: All CVT cases showed extensive thrombosis. Four patients had prior anticoagulation, and four had rHU > 1.00 with CT hyperdensity. The etiologies were heterogeneous. CVT thrombi were rich in red blood cells and displayed variable histological features, including signs of early organization. Compared to arterial thrombi, venous thrombi exhibited larger size (surface area 185.6 mm2 [IQR 83.0–237.9] vs. 21.8 mm2 [IQR 8.8–77.8]; p = 0.028) and lower fibrin content (16.6% [IQR 13.9–31.5] vs. 46.5% [IQR 25.1–49.5]; p = 0.036), with no other significant differences in composition. Low fibrin content and high RBC-to-fibrin ratio (R −0.9 and R 0.9, respectively; p = 0.047 for both) showed a significant correlation with rHU.

Conclusion: Our exploratory study first shows that CVT thrombi are larger than AIS thrombi, with higher RBC content and lower fibrin, matching CT density. These findings enhance the understanding of CVT pathophysiology but need validation.