title: Radiosurgery for low-grade intracranial arteriovenous malformations.
abstract: OBJECTIVE
  Low-grade, or Spetzler-Martin (SM) Grades I and II, arteriovenous malformations (AVMs) are associated with lower surgical morbidity rates than higher-grade lesions. While radiosurgery is now widely accepted as an effective treatment approach for AVMs, the risks and benefits of the procedure for low-grade AVMs, as compared with microsurgery, remain poorly understood. The authors of this study present the outcomes for a large cohort of low-grade AVMs treated with radiosurgery.
  
  
  METHODS
  From an institutional radiosurgery database comprising approximately 1450 AVM cases, all patients with SM Grade I and II lesions were identified. Patients with less than 2 years of radiological follow-up, except those with complete AVM obliteration, were excluded from analysis. Univariate and multivariate Cox proportional-hazards and logistic regression analyses were used to determine factors associated with obliteration, radiation-induced changes (RICs), and hemorrhage following radiosurgery.
  
  
  RESULTS
  Five hundred two patients harboring low-grade AVMs were eligible for analysis. The median age was 35 years, 50% of patients were male, and the most common presentation was hemorrhage (47%). The median AVM volume and prescription dose were 2.4 cm(3) and 23 Gy, respectively. The median radiological and clinical follow-up intervals were 48 and 62 months, respectively. The cumulative obliteration rate was 76%. The median time to obliteration was 40 months, and the actuarial obliteration rates were 66% and 80% at 5 and 10 years, respectively. Independent predictors of obliteration were no preradiosurgery embolization (p < 0.001), decreased AVM volume (p = 0.005), single draining vein (p = 0.013), lower radiosurgery-based AVM scale score (p = 0.016), and lower Virginia Radiosurgery AVM Scale (Virginia RAS) score (p = 0.001). The annual postradiosurgery hemorrhage rate was 1.4% with increased AVM volume (p = 0.034) and lower prescription dose (p = 0.006) as independent predictors. Symptomatic and permanent RICs were observed in 8.2% and 1.4% of patients, respectively. No preradiosurgery hemorrhage (p = 0.011), a decreased prescription dose (p = 0.038), and a higher Virginia RAS score (p = 0.001) were independently associated with postradiosurgery RICs.
  
  
  CONCLUSIONS
  Spetzler-Martin Grade I and II AVMs are very amenable to successful treatment with stereotactic radiosurgery. While patient, physician, and institutional preferences frequently dictate the final course of treatment, radiosurgery offers a favorable risk-to-benefit profile for the management of low-grade AVMs.
authors.affiliation: Department of Neurological Surgery, University of Virginia, Charlottesville, Virginia.
authors.forename: Dale
authors.initials: D
authors.lastname: Ding
authors.forename: Chun-Po
authors.initials: CP
authors.lastname: Yen
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Xu
authors.forename: Robert M
authors.initials: RM
authors.lastname: Starke
authors.forename: Jason P
authors.initials: JP
authors.lastname: Sheehan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D004621:Embolization, Therapeutic / Q000009:adverse effects / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000473:pathology / Q000601:surgery*; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000009:adverse effects / Q000379:methods*; D019106:Postoperative Hemorrhage / Q000453:epidemiology; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D012086:Reoperation / Q000706:statistics & numerical data; D012189:Retrospective Studies; D018570:Risk Assessment; D016896:Treatment Outcome; D055815:Young Adult
keywords: AVM = arteriovenous malformation; DSA = digital subtraction angiography; Gamma Knife; RBAS = radiosurgery-based AVM scale; RIC = radiation-induced change; SM = Spetzler-Martin; Virginia RAS = Virginia Radiosurgery AVM Scale; intracranial arteriovenous malformation; low Spetzler-Martin grade; stereotactic radiosurgery; stroke; vascular disorders; vascular malformation