en Neurosurgery Neurosurgery case report case report <p> <strong>Abstract</strong></p><p> <strong>Background: </strong>The Gamma Knife Radiosurgery (GKR) is an established management option for Cerebral Ar-teriovenous Malformations (AVMS). Therapeutic benefits of radiosurgery for arteriovenous malformations are complete obliteration of nidus with minimal neurological deficit.</p><p> <strong>Methods:</strong> Radiosurgery was performed between February 2003 and April 2010 at Kamraniye day clinic, Teh-ran, Iran, using the Leksell gamma knife model B (Elektra Instruments AB, Stockholm, Sweden) on 82 consecu-tive patients with AVMs. The male-to-female ratio was 1.4:1(48M, 34F). The age of the patients ranged from 9 to 70 years (mean, 28.5±12 years). The marginal dose to the AVM nidus was 45 to 85% (median, 60%) isodose and ranged from 14 to 30 Gy (mean, 20.57±13Gy).The maximum dose ranged between 20 to 60 Gy (mean, 37.5 Gy ± 10.17Gy ). Follow up of patients for complete AVM obliteration and in the case of complications MRI were performed.</p><p> <strong>Results:</strong> Complete obliteration of AVM was achieved in 56 cases (68.29%). It was marked in average 3.62 [SD=3.19] years (from 1 to 5 years) after GKR. Partial obliteration (≥50% reduction of the nidus volume) was marked in 24 cases(31%), and less than 50% reduction of the nidus volume was marked in 2 cases(2.4%) with a follow-up of 5 years. Complete obliteration of AVM had statistically significant associations with smaller score of Spetzler-Martin arteriovenous malformation grading system for AVMs. (p< 0.05)</p><p> <strong>Conclusion:</strong> The Gamma Knife Radiosurgery can offer total and partial obliteration to acceptable percent of treated AVM with a low risk of morbidity. Higher success observed in patients with Spetzler-Martin Grade I and II AVMs, which was attributed to smaller volume of AVMs in this group.</p><p>  </p> Gamma Knife Radiosurgery (GKR), Arteriovenous malformations, Obliteration rate 119 126 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-1-243&slc_lang=en&sid=1 Maziar Azar maziarazar@yahoo.com 20031947532846002622 20031947532846002622 No Tehran University of Medical Sciences, Tehran, Iran. Farid Kazemi Gazik faridkazemi@lide.com 20031947532846002623 20031947532846002623 No Tehran University of Medical Sciences, Tehran, Iran. Mahdi Nikoobakht mnikobakht@gmail.com 20031947532846002624 20031947532846002624 Yes Tehran University of Medical Sciences, Tehran, Iran. Address: 4th floor,# 9, Snd Golbarg St., Kharazmi St., Mollasadra Ave.,Tehran, Iran. Mohamad-Reza Yousefi dr_yousefi1980@yahoo.com 20031947532846002625 20031947532846002625 No Tehran University of Medical Sciences, Tehran, Iran. Yaser Ghavami ghavami.y@gmail.com 20031947532846002626 20031947532846002626 No