Diagnosis: Radiation Necrosis

History: The patient is a 25 year old man who initially presented s/p snow mobile accident with multiple hemorrhagic contusions. On initial evaluation, the patient was incidentally noted to have a left temporal Arteriovenous Malformation. This AVM was subsequently treated with Gamma Knife therapy. The patient now presents 12 months later with no complaints for routine follow up.

Findings: •12 months following gamma knife therapy, follow up imaging revealed a rim-enhancing mass in the left temporal lobe adjacent to the posterior horn of the left ventricle. Surrounding this lesion is extensive T2-high signal, likely representing edema. • Initial MR images show malacic changes in the frontal lobes with an incidental prominent vascular structures suggestive of a developmental venous anomaly. •Arteriogram also performed to therapy confirmed the presence of an AVM, predominantly fed by left lateral posterior choroidal artery.

Ddx: •Radiation Necrosis •New Primary Brain neoplasm •Metastatic disease • Infectious process

Dxhow: • Biopsy revealed necrotic tissue consistent with radiation necrosis. • MR spectroscopy