title: Gamma Knife surgery for basal ganglia and thalamic arteriovenous malformations.
abstract: OBJECTIVE
  Gamma Knife surgery (GKS) has emerged as the treatment of choice for small- to medium-sized cerebral arteriovenous malformations (AVMs) in deep locations. The present study aims to investigate the outcomes of GKS for AVMs in the basal ganglia and thalamus.
  
  
  METHODS
  Between 1989 and 2007, 85 patients with AVMs in the basal ganglia and 97 in the thalamus underwent GKS and were followed up for more than 2 years. The nidus volumes ranged from 0.1 to 29.4 cm(3) (mean 3.4 cm(3)). The mean margin dose at the initial GKS was 21.3 Gy (range 10-28 Gy). Thirty-six patients underwent repeat GKS for residual AVMs at a median 4 years after initial GKS. The mean margin dose at repeat GKS was 21.1 Gy (range 7.5-27 Gy).
  
  
  RESULTS
  Following a single GKS, total obliteration of the nidus was confirmed on angiograms in 91 patients (50%). In 12 patients (6.6%) a subtotal obliteration was achieved. No flow voids were observed on MR imaging in 14 patients (7.7%). Following single or repeat GKS, total obliteration was angiographically confirmed in 106 patients (58.2%) and subtotal obliteration in 8 patients (4.4%). No flow voids on MR imaging were observed in 18 patients (9.9%). The overall obliteration rates following one or multiple GKSs based on MR imaging or angiography was 68%. A small nidus volume, high margin dose, low number of isocenters, and no history of embolization were significantly associated with an increased rate of obliteration. Twenty-one patients experienced 25 episodes of hemorrhage in 850 risk-years following GKS, yielding an annual hemorrhage rate of 2.9%. Four patients died in this series: 2 due to complications of hemorrhage and 2 due to unrelated diseases. Permanent neurological deficits caused by radiation were noted in 9 patients (4.9%).
  
  
  CONCLUSIONS
  Gamma Knife surgery offers a reasonable chance of obliterating basal ganglia and thalamic AVMs and does so with a low risk of complications. It is an optimal treatment option in patients for whom the anticipated risk of microsurgery is too high.
authors.affiliation: Department of Neurological Surgery, University of Virginia Health System, Charlottesville, VA, USA.
authors.forename: Ching-Hsiao
authors.initials: CH
authors.lastname: Cheng
authors.forename: R Webster
authors.initials: RW
authors.lastname: Crowley
authors.forename: Chun-Po
authors.initials: CP
authors.lastname: Yen
authors.forename: David
authors.initials: D
authors.lastname: Schlesinger
authors.forename: Mark E
authors.initials: ME
authors.lastname: Shaffrey
authors.forename: Jason P
authors.initials: JP
authors.lastname: Sheehan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001164:Arteriovenous Fistula / Q000175:diagnosis / Q000601:surgery*; D001479:Basal Ganglia / Q000098:blood supply*; D020144:Basal Ganglia Cerebrovascular Disease / Q000175:diagnosis / Q000601:surgery*; D002533:Cerebral Angiography; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000175:diagnosis / Q000601:surgery*; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000209:etiology / Q000601:surgery; D016634:Radiosurgery / Q000379:methods*; D012086:Reoperation; D013786:Thalamic Diseases / Q000175:diagnosis / Q000601:surgery*; D013788:Thalamus / Q000098:blood supply*; D055815:Young Adult