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George J. Kaptain, Jason P. Sheehan, and Neal F. Kassell

right ). Cerebral angiographic studies revealed a lenticulostriate artery aneurysm, although the junction of the lesion with the parent vessel could not be demonstrated ( Fig. 2 ). A frontotemporal approach through the hematoma cavity revealed a spherical dilation of a lenticulostriate artery. The aneurysm was excised along with the feeding artery, and histopathological analysis revealed absence of the elastic lamina of the aneurysm wall without inflammatory changes or evidence of an infectious source. After a complicated hospital course, the infant was discharged. At

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Douglas Kondziolka

factors. Early reduction in flow following radiosurgery may increase obliteration rates and decrease the length of the period in which the patient is at risk of hemorrhage. Of course, postradiosurgical endovascular repair of an associated aneurysm seems important. In this series, only 6% of patients had associated aneurysms, 1 a number less than that reported by some other authors who have noted associated aneurysms in up to 50% of patients. I think that our understanding of why an AVM ruptures is far from complete. We need to better understand how flow dynamics, blood

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Clival encephalocele

Case illustration

George J. Kaptain, David A. Vincent, Jason P. Sheehan, and Edward R. Laws Jr.

the nasopharynx, using a sublabial—transseptal approach. The posterior wall of the sphenoid sinus (anterior wall of the clivus) was thin, covering the underlying encephalocele. The bone was removed, the stalk was mobilized and secured with an aneurysm clip ( Fig. 3 ), and the distal encephalocele was resected. The resulting defect and the sphenoid sinus were packed with abdominal fat. Fig. 1. Midsagittal T 2 -weighted MR image revealing a soft-tissue mass extending through the clivus (double arrow) into the nasopharynx (large arrow) . Fig. 2. Upper: Axial CT

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Robert M. Starke, Chun-Po Yen, Dale Ding, and Jason P. Sheehan

ganglia, thalamus, or brainstem 264 (26.1) 0.79 0.58–1.06 0.119 eloquent location of AVM 677 (66.9) 0.62 0.47–0.82 0.001 mean AVM vol ± SD (cm 3 ) 3.5 ± 3.3 0.80 0.76–0.84 <0.001 AVM diameter  0–3 cm 799 (79.0) 1.00  3–6 cm 213 (21.0) 0.30 0.22–0.41 <0.001 mean maximal diameter ± SD (cm) 2.28 ± 0.91 0.45 0.39–0.53 <0.001 deep venous drainage 526 (52.0) 0.95 0.74–1.23 0.708 associated aneurysm 97 (9.6) 0.75 0.49–1.14 0.181 history of embolization 244 (24.1) 0

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Jason P. Sheehan, Douglas Kondziolka, John Flickinger, and L. Dade Lunsford

Instruments, Atlanta, GA). The GKS methodology used to treat pituitary lesions is described in detail elsewhere. 36 An MR image of the sellar region was obtained for each patient by using a 1.5-tesla imager. One-millimeter-thick axial slices with volume acquisition, fat suppression, and intravenous gadolinium contrast were obtained. In all cases prior to 1989 or when a patient could not undergo MR imaging (for example, because of a non—MR imaging compatible aneurysm clip or a pacemaker), high-resolution 1-mm-thick axial CT scans with intravenous contrast were obtained

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Dale Ding, Chun-Po Yen, Robert M. Starke, Zhiyuan Xu, and Jason P. Sheehan

draining veins in 198 patients (35.0%). Associated aneurysms, defined as those on feeding arteries in, or proximal to, the nidus, were present in 32 cases (5.7%) including 13 intranidal aneurysms (2.3%) and 19 perinidal aneurysms (3.4%). The Spetzler-Martin grade, which factors in AVM diameter, superficial or deep venous drainage, and eloquence of involved cortex, was I in 71 patients (12.6%), II in 179 patients (31.7%), III in 252 patients (44.6%), IV in 63 patients (11.1%), and V in 0 patients. 44 The radiosurgery-based AVM score (RBAS), which factors in patient age

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David J. Schlesinger, Håkan Nordström, Anders Lundin, Zhiyuan Xu, and Jason P. Sheehan

volume is increased. 48 Embolic Agents and Potential Effects on Delivered Dose Distribution Embolization of AVMs is also playing an increasingly important role, often as an adjuvant treatment to radiosurgery or microsurgery, with the goal to reduce the nidal volume of large AVMs and minimize the risks of any intranidal aneurysms and arteriovenous fistulas. 1 , 11 , 14 , 15 Unfortunately, in a small subset of patients, GKRS fails to result in complete obliteration of the AVM nidus, prolonging the risk of hemorrhage and, in most cases, necessitating retreatment of the

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Adomas Bunevicius, Darrah Sheehan, Mary Lee Vance, David Schlesinger, and Jason P. Sheehan

rates across neurosurgical procedures, including transsphenoidal resection of pituitary adenomas, 4 excision of vestibular schwannomas, 2 , 18 the clipping 11 and coiling 1 of intracranial aneurysms, and scoliosis correction surgery, 8 among others. However, to the best of our knowledge, there are no studies evaluating the possible association of experience with GKRS and treatment outcomes of patients with CD. The goal of this study was to evaluate the possible association of the era of GKRS (as a proxy of the center’s experience and technological advancements

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Or Cohen-Inbar, Cheng-Chia Lee, Zhiyuan Xu, David Schlesinger, and Jason P. Sheehan

, Schwab K : The natural history of symptomatic arteriovenous malformations of the brain: a 24-year follow-up assessment . J Neurosurg 73 : 387 – 391 , 1990 25 Perret G , Nishioka H : Report on the cooperative study of intracranial aneurysms and subarachnoid hemorrhage. Section VI Arteriovenous malformations An analysis of 545 cases of cranio-cerebral arteriovenous malformations and fistulae reported to the cooperative study . J Neurosurg 25 : 467 – 490 , 1966 26 Pollock BE , Flickinger JC : A proposed radiosurgery-based grading system for

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Dale Ding, Chun-Po Yen, Zhiyuan Xu, Robert M. Starke, and Jason P. Sheehan

intranidal aneurysms and those with intranidal arteriovenous shunts. For the majority of low-grade AVMs, the neoadjuvant role of embolization prior to microsurgery or radiosurgery seems similarly minor. However, as advances in endovascular technology continue to be made and our understanding of multimodality AVM treatment continues to evolve, the impact of embolization on AVMs, such as after rather than before radiosurgery, has yet to reach its maximum potential. Role of Radiosurgery for Treatment of SM Grade I and II AVMs In a large cohort of low-grade AVM patients