Object: Posterior fossa arteriovenous malformations (AVMs) are relatively uncommon and often difficult to treat. The authors present their experience with multimodality treatment of 76 posterior fossa AVMs, with an emphasis on Spetzler-Martin Grades III-V AVMs.
Methods: Seventy-six patients with posterior fossa AVMs treated with radiosurgery, surgery, and endovascular techniques were analyzed.
Results: Between 1982 and 2006, 36 patients with cerebellar AVMs, 33 with brainstem AVMs, and 7 with combined cerebellar-brainstem AVMs were treated. Natural history data were calculated for all 76 patients. The risk of hemorrhage from presentation until initial treatment was 8.4% per year, and it was 9.6% per year after treatment and before obliteration. Forty-eight patients had Grades III-V AVMs with a mean follow-up of 4.8 years (range 0.1-18.4 years, median 3.1 years). Fifty-two percent of patients with Grades III-V AVMs had complete obliteration at the last follow-up visit. Three (21.4%) of 14 patients were cured with a single radiosurgery treatment, and 4 (28.6%) of 14 with 1 or 2 radiosurgery treatments. Twenty-one (61.8%) of 34 patients were cured with multimodality treatment. The mean Glasgow Outcome Scale (GOS) score after treatment was 3.8. Multivariate analysis performed in the 48 patients with Grades III-V AVMs showed radiosurgery alone to be a negative predictor of cure (p = 0.0047). Radiosurgery treatment alone was not a positive predictor of excellent clinical outcome (GOS Score 5; p > 0.05). Nine (18.8%) of 48 patients had major neurological complications related to treatment.
Conclusions: Single-treatment radiosurgery has a low cure rate for posterior fossa Spetzler-Martin Grades III-V AVMs. Multimodality therapy nearly tripled this cure rate, with an acceptable risk of complications and excellent or good clinical outcomes in 81% of patients. Radiosurgery alone should be used for intrinsic brainstem AVMs, and multimodality treatment should be considered for all other posterior fossa AVMs.