Ahead of Print: MRI of AVMs After Radiosurgery

Background: Stereotactic radiosurgery is ideal for treating small cerebral arteriovenous malformations that are surgically inaccessible. However, given the inherent delay of AVM obliteration and the potential for radiosurgical failure, detailed evaluation of the neurovascular architecture is necessary to monitor persistence of residual flow. Modern imaging systems such as MRI and angiography allow clinicians to assess transnidus flow after radiosurgical intervention.

Objective: To determine the accuracy of an MRI diagnosis of complete thrombosis and identify variables that affect the precision of MRI assessment.

Methods: 120 patients were reviewed after receiving radiosurgery at the University of Florida from 1990-2010. Each patient had an MRI demonstrating AVM obliteration and an angiogram either confirming or denying AVM thrombosis.

Results: MR imaging correctly predicted complete AVM obliteration in 82% of patients. There was a significant correlation between AVM volume and MRI accuracy in two separate models. In the first model, logistic regression analysis revealed a significant linear relationship between the natural log of AVM volume and MRI accuracy. The second model showed significant evidence of a cutoff point in MRI accuracy near an AVM volume of 2.80cm3, above which MRI agreement with angiography is 90%, and below which MRI agreement falls off sharply to remain constant at 70%.

Conclusion: MR imaging is a useful diagnostic system for assessing AVM obliteration, but its accuracy is inherently linked to the nidus volume it is measuring. These results suggest MRI may be able to take on an increasingly independent role in the evaluation of AVM regression.

From: Magnetic Resonance Imaging Assessment of Cerebral Arteriovenous Malformation Obliteration After Stereotactic Radiosurgery by O’Connor et al.

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