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Steiner L, Lindquist C, Adler J, Torner J, Alves W, Steiner M: Clinical outcome of radiosurgery for cerebral arteriovenous malformations.

Journal of Neurosurgery 77:1. 1992 Freidman W, Blatt D, Bova F, Buatti J, Mendenhall W, Kubilis P: The risk of hemorrhage after radiosurgery for arteriovenous malformations.

Journal of Neurosurgery 84:912. 1996 Flickinger J, Pollack B, Knodziolka D, Lunsford L: A dose-response analysis of arteriovenous malformation obliteration after radiosurgery.

Int J radiation Oncology Biol Phys 36:873. 1996 Flickinger J, Pollack B, Knodziolka D, Maitz A, Lunsford L: Complications from arteriovenous malformation radiosurgery: Multivariate analysis and risk modeling. Int J radiation Oncology Biol Phys 38:485. 1997 Karlsson B, Lindquist C, Steiner L: Prediction of obliteration after gamma knife surgery for cerebral arteriovenous malformations. Neurosurgery 40:425. 1997

Sasaki T, Kurita H, Saito I, et al: Arteriovenous malformations in the basal ganglia and thalamus: management and results in 101 cases.

Journal of Neurosurgery 88:285, 1998 Pollack B: Stereotactic radiosurgery for arteriovenous malformations. Neurosurgery Clinics of North America 10:281, 1999

Steiner L, Lindquist C, Adler J, Torner J, Alves W, Steiner M: Clinical outcome of radiosurgery for cerebral arteriovenous malformations.

Journal of Neurosurgery 77:1. 1992 Freidman W, Blatt D, Bova F, Buatti J, Mendenhall W, Kubilis P: The risk of hemorrhage after radiosurgery for arteriovenous malformations.

Journal of Neurosurgery 84:912. 1996 Flickinger J, Pollack B, Knodziolka D, Lunsford L: A dose-response analysis of arteriovenous malformation obliteration after radiosurgery.

Int J radiation Oncology Biol Phys 36:873. 1996 Flickinger J, Pollack B, Knodziolka D, Maitz A, Lunsford L: Complications from arteriovenous malformation radiosurgery: Multivariate analysis and risk modeling. Int J radiation Oncology Biol Phys 38:485. 1997 Karlsson B, Lindquist C, Steiner L: Prediction of obliteration after gamma knife surgery for cerebral arteriovenous malformations. Neurosurgery 40:425. 1997

Sasaki T, Kurita H, Saito I, et al: Arteriovenous malformations in the basal ganglia and thalamus: management and results in 101 cases.

Journal of Neurosurgery 88:285, 1998 Pollack B: Stereotactic radiosurgery for arteriovenous malformations. Neurosurgery Clinics of North America 10:281, 1999

embolization was unsuccessful or (4) residual deep AVM remains after surgery. Stereotactic radiosurgery can be particularly useful for patients with deep AVMs, such as those in the basal ganglia or brain stem, or AVMs in critical lobar areas, such as sensorimotor cortex. Radiosurgery becomes the preferred treatment when surgical mortality and morbidity exceed 4 and 12%, respectively. Pregnant patients are not candidates for radiosurgery.

The procedure is relatively straightforward. First, a stereotactic head-frame is placed using local anesthesia and mild sedation. The patient then undergoes an MRI scan and a stereotactic cerebral angiogram. Using these images, the neurosurgeon, radiation physicist and radiation therapist can then plan treatment. The selected target dose depends on the exact configuration of the AVM. In general, a radiation dose of about 20 Gy is administered to the margin of the AVM nidus [21]. Obliteration rates of 70, 80 or 90% have been observed when the radiation dose to the AVM margin is 16, 18 or 20 Gy, respectively. The prescription isodose (radiation dosage)-to-treatment-volume ratio should preferably be less than 2; however, this may be difficult to achieve with irregular contours. After treatment, patients are observed overnight in the hospital. We administer peri-procedural anticonvulsants and steroids to our patients.

AVMs are followed after radiosurgery with MRI, until there is no evidence of nidal flow. Once this occurs, follow-up catheter angiography is performed to document AVM obliteration.

Stereotactic radiosurgery is relatively safe and is not associated with the conventional risks of surgery, such as bleeding or infection. Acute, transient radiation risks causing neurologic deficits are uncommon and generally respond to steroids. Instead, the major risks of radiosurgery are delayed. These risks include primary AVM hemorrhage during the latency period before obliteration and the risk of delayed radiation injury. Subtotal AVM obliteration by stereotactic radiosurgery is of no benefit in preventing hemorrhage. This is confirmed by several clinical series demonstrating that the risk of hemorrhage between AVM treatment and obliteration is unchanged from the expected natural history of AVM hemorrhage. It remains between 2 and 4% per year. Successful obliteration can take up to 2-3 years after radiosurgery. Delayed radiation injury, such as radiation necrosis of cortical tissue or cranial nerves surrounding the AVM nidus, is related to the radiation dose, volume treated, patient age and AVM flow characteristics [13]. Radiation-induced tumors are very rare and generally occur many years after treatment. Radiation-related complications are correlated with the

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