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Huai-che Yang, Hideyuki Kano, Nasir Raza Awan, L. Dade Lunsford, Ajay Niranjan, John C. Flickinger, Josef Novotny Jr., Jagdish P. Bhatnagar and Douglas Kondziolka

T he incidence of clinically recognized vestibular schwannomas (acoustic neuromas) is approximately 1:100,000 in the US population. 2 Because these lesions are generally benign tumors, the goals of treatment include long-term tumor control and maintenance of existing cranial nerve function. Stereotactic radiosurgery is a safe and effective tool in patients with vestibular schwannoma. 1 , 3–5 , 9 , 11 , 13–15 , 19 The role of SRS in the management of large vestibular schwannomas (> 3 cm) remains controversial. The potential for AREs and lack of rapid volume

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Hideyuki Kano, John C. Flickinger, Aya Nakamura, Rachel C. Jacobs, Daniel A. Tonetti, Craig Lehocky, Kyung-Jae Park, Huai-che Yang, Ajay Niranjan and L. Dade Lunsford

M anagement of large-volume arteriovenous malformations (AVMs) poses significant challenges to patients and physicians. For such AVMs, selected centers began to stage treatment volumes of the AVM using stereotactic radiosurgery (SRS). To date few published reports exist to validate the long-term results of this strategy. 1 , 3 , 9 , 12 , 18 , 19 The obliteration response of an AVM depends on radiation dose and volume, but for larger volumes, the dose must be reduced to decrease radiation-related brain injury. In 1992, we began to stage anatomical components of

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Edward H. Oldfield

would not be candidates for surgical treatment. The HBs treated by SRS are smaller, generally so small that they are not producing symptoms, and are less likely to have an associated cyst than are the HBs treated with surgery. For instance, in the Kano series of SRS the mean tumor size was 0.9 cm 3 for the 335 treated tumors in the VHL patients. This compares to an average size of 2.4 cm 3 in the NIH surgical series of all 164 cerebellar HBs in VHL, 2 4.0 cm 3 in the 46 HBs (28%) not associated with cysts, but 16.5 cm 3 total volume in the 118 HBs (72

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Arteriovenous malformations and radiosurgery

Douglas Kondziolka, Hideyuki Kano and L. Dade Lunsford

critical but relatively rare vascular disorder presents a wide spectrum of features that influence decision making, management options, and outcomes: volume, anatomical location, symptoms, signs, blood flow, occurrence of prior bleeding events, presence of associated aneurysms, venous outflow, and age at presentation. The overriding risk for patients is the risk of often tragic brain hemorrhage and death. Previous publications on the natural history of untreated AVMs as well as management publications that define outcomes at AVM centers of excellence have improved our

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Gillian Harrison, Hideyuki Kano, L. Dade Lunsford, John C. Flickinger and Douglas Kondziolka

visits and serial imaging analyses. Commonly, clinicians may describe the imaging response categorically as regressed, enlarged, or stable and, if measured, use simple measurements of tumor diameter. Although this evaluation may suffice for immediate management, qualitative descriptions of response do little to characterize the true nature of tumor response after any form of therapy. Additionally, given the heterogeneous nature of meningiomas and the possibility of distant recurrence or delayed malignant progression, 4 , 22 quantitative characterization of volume

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Hideyuki Kano, Ajay Niranjan, Douglas Kondziolka, John C. Flickinger and L. Dade Lunsford

option. In these patients a diagnosis was based on a combination of clinical symptoms or signs and confirmatory neuroimaging findings. All tumors extended along the course of the trigeminal nerve, showed diffuse contrast enhancement on MR imaging, and had no dural tail. Six patients underwent SRS at the time of tumor recurrence identified on imaging. Tumor progression after initial treatment was defined as an increase in lesion volume demonstrated on MR imaging. The median duration between the last excision and tumor progression was 22.1 months (range 9.4–76.5 months

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Douglas Kondziolka, Seyed H. Mousavi, Hideyuki Kano, John C. Flickinger and L. Dade Lunsford

still have useful or even normal hearing. The anticipated growth pattern (using average diameters) of newly diagnosed vestibular schwannomas has been estimated to be one of the following 3 types: 1) no or very slow growth; 2) slow growth (2 mm/year linear growth on imaging studies); or 3) fast growth (> 8 mm/year). In certain cases a doubling of tumor volume within 12 months has been reported. In fact, the tumor volume doubling time may be a better measure of tumor growth than average tumor diameter. 63 Cystic vestibular schwannomas occasionally demonstrate early

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Hideyuki Kano, Douglas Kondziolka, Aftab Khan, John C. Flickinger and L. Dade Lunsford

of a Model G Leksell stereotactic frame after inducing conscious sedation and applying a local scalp anesthetic, except in younger children in whom general anesthesia was induced. The tumor was then visualized using high-resolution 3D spoiled gradient recalled acquisition in steady state sequence MR imaging after intravenous contrast enhancement. Fast spin echo T2-weighted MR images were acquired to evaluate tumor extent and inner ear structures. We obtained images of the cochlea, vestibule, and semicircular canals using T2-weighted volume-acquisition MR imaging

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Seong-Hyun Park, Hideyuki Kano, Ajay Niranjan, John C. Flickinger and L. Dade Lunsford

Pittsburgh Medical Center. We excluded patients with neurofibromatosis, multiple meningiomas, those with fewer than 3 months of follow-up, and those whose prior surgical histology indicated that the tumor was atypical or anaplastic. Cerebellopontine angle meningiomas were defined as tumors whose maximal volume was centered at the anatomical junction of the lateral cerebellum, the pons, and the internal auditory meatus. The bulk of the tumor was superior to the jugular foramen and inferior to the trigeminal nerve. We did not include meningiomas that appeared to arise from

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Daniel Tonetti, Hideyuki Kano, Gregory Bowden, John C. Flickinger and L. Dade Lunsford

procedure range from 70% to 80% over 5 years in selected groups, depending on AVM volume, dose delivered, location, and patient age. 1 , 5 , 6 , 8 , 13 , 19 , 25 , 29 , 33 , 35 The median time until MRI documentation of total obliteration of AVMs after Gamma Knife SRS (Elekta AB) has been shown to be 36 months. 16 Although various publications have addressed the risk for AVM hemorrhage during pregnancy, 4 , 7 , 11 , 15 , 28 , 32 such studies have not assessed the risk for hemorrhage in women who become pregnant during the typical 3-year latency interval between SRS and