Clinical Features and Classification of Brain AVMs and Cranial DAVFs

The clinical findings of intracranial vascular malformations are strictly related to their morphologic, angioarchitectural and hemodynamic characteristics. An overall study of these features is the first step to understand the different classifications for arteriovenous malformations, dural arteriovenous fistulas and carotid-cavernous fistulas. This evaluation will also suggest the correct timing of endovascular treatment and which part of the lesion should be the target of the therapy. Conventional cerebral angiography is mandatory when a correct classification of intracranial arteriovenous malformative shunts must be achieved. The angioarchitectural classification of brain arteriovenous malformations considers all angiographic features of each component of the malformation, both morphologically and hemodynamically, and relates them to the clinical course of the disease. The correlation between clinical findings, angiographic features and classifications is even stronger for cranial dural arteriovenous fistulas, in which cortical venous drainage is typical of "aggressive" fistulas and is usually absent in the "benign" type. Similarly, carotid-cavernous fistulas can be differentiated at angiography into high or low flow lesions according to the flow rate of the shunt, and into direct or indirect fistulas, according to the origin of arterial feeders. This paper focuses on the existing relation between the hemodynamics of brain arteriovenous malformations, cranial dural arteriovenous fistulas, carotid-cavernous fistulas, and their most frequent clinical findings, through an analysis of the most widely used different classification systems.