Relationships between hemorrhage, angioarchitectural factors and collagen of arteriovenous malformations

While associations between the angioarchitecture of arteriovenous malformations (AVMs) in the brain and pathological features have been described, here we investigated the relationship between the angioarchitecture, the pathological features of the vessel wall, and hemorrhagic events. The study was conducted on 43 patients: 16 with ruptured AVM (rAVM), 15 with non-ruptured AVM (nrAVM), 6 with craniocerebral trauma (control) and 6 with epilepsy (control). The diagnosis of AVM was confirmed by preoperative digital subtraction angiography. Tissues were stained with hematoxylin and eosin and Masson's trichrome (for collagen fibers) to evaluate the vessel wall structure and endothelial integrity. The content and distribution of collagen types I and III in the vessel wall were assessed by immunohistochemical staining. In the nrAVM group, the nidus had more draining veins than the rAVM group (P < 0.05). Severely damaged endothelial cells, significantly fewer smooth muscle cells in the media, and hyperplasic type-I and -III collagen fibers were found in the rAVM group. The content of collagen types I and III in rAVMs was higher than that in the nrAVM (P < 0.05) and control groups (P < 0.01). There is an association between angioarchitectural features such as the number of draining veins and the pathological structure of the AVM wall. These abnormalities may contribute to AVM rupture.