Correlation of magnetic resonance characteristics and histopathological type of angiographically occult vascular malformations

OBJECTIVE: Histological and radiological classification of vascular malform ations has previously been attempted in an effort to understand their natur e and predict their biological behavior. There exists a subgroup of vascula r malformations that are angiographically occult and share a common magneti c resonance imaging (MRI) appearance but may differ in their behavior. We s ought to determine any correlation between MRI features and final histopath ological diagnosis. METHODS: We reviewed our series of 72 patients with angiographically occult vascular malformations operated on at Stanford University Medical Center b etween 1988 and 1993. Radiographic magnetic resonance images and histopatho logical specimens were retrospectively evaluated for various diagnostic fea tures. RESULTS: Our data indicate that lesions exhibiting a ring of hemosiderin ar e associated with the presence of a cavernous malformation (CM) component ( 86% of CMs versus 33% of non-CM lesions). A lesion associated with edema, m ass effect, or a single prominent blood product on MRI correlates with the presence of an arteriovenous malformation (AVM) component. Sixty-three perc ent of AVMs and 80% of lesions with partial AVM components showed edema, co mpared with 8% of CMs and 0% of venous malformations. Sixty percent of AVMs and 63% of lesions with partial AVM components showed a single prominent b lood product, compared with 8% of CMs and 0% of venous malformations. Final ly, 60% of AVMs exhibited mass effect, compared with 20% of CMs. Additional ly, an expansile hemorrhage is suggestive of an AVM. CONCLUSION: This study is the first to demonstrate that a particular MRI ap pearance of an angiographically occult vascular malformation is suggestive of an AVM component. This may have important implications with regard to th e behavior of the lesion and planning of future treatment.