60 year-old female with SRS for AVM.TECHNIQUE :1. Multiplanar and multi-sequence MR images of the brain were obtained with and without contrast, with intravenous administration of 18 cc Multihance.2. MR angiogram of the circle of Willis was performed without contrast . MRI Brain:There is no diffusion restriction to suggest acute infarction.In the area of previously seen AVM involving the cerebellar vermis and and left paramedian cerebellar hemisphere, there remains high T2/FLAIR signal and susceptibility artifact, with evidence suggesting encephalomalacia and surrounding hemosiderin deposition indicating prior hemorrhage. These findings are not significantly changed in appearance or extent. The adjacent fourth ventricle is mild to moderately dilated, also stable from several previous exams. T2/FLAIR periventricular and subcortical hyperintense white matter changes are unchanged, suggestive of chronic small vessel ischemic disease.There has been mild interval decrease in enhancement of the affected area of the cerebellar vermis, paramedian left cerebellar hemisphere, and especially in the left occipital lobe. Total area of enhancement measures approximately 13 x 18 mm on coronal images, from previously 17 x 21 mm, and is suggestive of radiation necrosis.Small 8mm dural based avidly enhancing left posterior temporal lobe lesion unchanged, compatible with small meningioma.The remainder of the ventricular system and sulci are within normal limits. The cisterns remain patent. No extra-axial fluid collection is identified.The cerebellar tonsils are in normal position. Pituitary gland is unremarkable. The midline structures and craniocervical junction are within normal limits. Left maxillary mucous retention cyst. Mastoid air cells are clear.MRA Brain:Antegrade flow is present in the distal internal carotid arteries, the distal vertebral arteries, the basilar artery and the proximal anterior, middle and posterior cerebral arteries.The left superior cerebellar artery supplying the AVM has further regressed in caliber, particularly its distal aspect, as has the draining vein. A transosseus branch of the left occipital artery previously seen to partially supply the AVM is no longer visible.There is no evidence for intracranial aneurysm or cerebrovascular occlusion.The anterior communicating artery is identified. The posterior communicating arteries are not readily identified. The vertebral arteries are similar in size.
1.Further regression in caliber of supplying arteries and draining vein of the known, remotely hemorrhagic, cerebellar vermian AVM. Although no AVM is clearly demonstrated on the MRA exam, residual AVM cannot be excluded on the basis of this exam.2.Enhancement in the cerebellum where the AVM was and in the adjacent occipital lobe is suggestive of radiation necrosis. It has decreased compared to the previous exam.