Magnetic Resonance Perfusion Changes of Arteriovenous Malformations Treated with Stereotactic Radiosurgery.

BACKGROUND: The latency period from stereotactic radiosurgery (SRS) to obliteration of arteriovenous malformations (AVM) requires continuous imaging surveillance. Magnetic resonance (MR) perfusion is promising for noninvasive monitoring of AVMs after SRS. We studied longitudinal MR perfusion changes of brain AVMs treated with SRS. METHODS: Consecutive patients treated for brain AVMs using SRS who had MR perfusion imaging studies performed before and at least once after SRS were studied. We estimated ipsilateral/contralateral brain hemisphere ratios of MR perfusion indexes, including regional cerebral blood flow (rCBF) and relative cerebral blood volume (rCBV), in the AVM nidus, perinidal region, and remote anterior and posterior brain regions. RESULTS: Eleven patients (6 women; median age, 21 years) underwent SRS (median prescription dose, 18 Gy; range, 12-20 Gy) for brain AVMs (median Spetzler-Martin grade 2 and median volume 4.6 mL). Before the SRS, rCBV and rCBF ratios were significantly higher in the AVM nidus compared with other investigated brain regions (P < 0.001). Median time from SRS to the first and last post-SRS MR perfusion studies was 8 and 35 months, respectively. There was a statically significant decrease of rCBV (P = 0.043) and rCBF (P = 0.036) ratios in the AVM nidus, but not other brain regions, during post-SRS follow-up. CONCLUSIONS: There is a gradual decrease of rCBV and rCBF in the AVM nidus after SRS. MR perfusion imaging is promising for monitoring of hemodynamic changes of AVMs after SRS. Larger studies investigating clinical value of MR perfusion imaging for AVMs after SRS are warranted.

Gamma Knife radiosurgery associated worsening of superficial siderosis due to a foramen magnum tumor - A case report.

Superficial siderosis (SS) of the brain results from a chronic iron toxicity due to repeated microscopic leakage of blood products into the subarachnoid space. We report on Gamma Knife Radiosurgery (GKRS) associated worsening of superficial siderosis in a patient with skull-base tumor. A 73 year-old male patient presented with clumsiness and gait ataxia and was diagnosed with foramen magnum meningioma. He was also noted to have superficial siderosis involving the mainly the infratentorial compartment. After a thorough evaluation of craniospinal axis, no other cause of bleeding was identified. Patient was treated with the GKRS. After GKRS, there was an initial radiological and clinical worsening of SS starting at 6 months and peaking at 2 years. The disease stabilized and showed mild reduction at 3 years. GKRS lead to an initial progression of superficial siderosis. However, over a longer period, tumor control and improvement of the siderosis was observed.