1000. Presentation and Multi-modality Treatment of Posterior Fossa Arteriovenous Malformations

Authors: Brooke T. Kennamer; George Klironomos, MD; Kevin Kwan, MD; Julia Schneider, BS; Andrew Kobets, MD; Jeffrey Katz, MD; David Chalif, MD, FACS; Amir Dehdashti, MD, FACS (Hoboken, NJ)

Introduction: Posterior fossa arteriovenous malformations (AVMs) are relatively uncommon and among the most challenging lesions to treat in neurosurgery. We present multimodality treatment of posterior fossa AVMs. Methods: A retrospective review from a prospectively maintained database was performed to identify patients with posterior fossa AVMs treated at Northwell Health in 2007-2017. AVMs were characterized based on involvement of the cerebellar hemisphere (tentorial, suboccipital, vermian, petrosal, tonsillar) or the brainstem. Correlations between SRS treated and surgically treated patients were examined using Kruskal-Wallis and Fisher tests for bivariate analysis. Subsequent multivariate analysis was conducted in R Studio. Results: The cohort consisted of 47 patients, 21 males and 26 females. AVMs were most commonly located in the suboccipital region (34%) and vermian (44.7%). Average size of the AVM was 1.5cm (SD±0.82) and average Spetzler-Martin grade was 1.78 (SD±0.72). Forty-three patients (91.5%) received embolization and 29 patients (61.7%) received surgery. None of surgical patients had evidence of residual AVM. The most common surgical complication was infection. Nine patients (19.1%) received SRS and five had multiple SRS treatments. Three of the SRS patients had a postoperative complication (33.3%). Average follow up time was 24 months (SD±27.4) with average modified Rankin scores of 1.7 (SD±1.7). Fisher Exact tests were significant for patients who were treated with SRS being more likely to have no evidence of hemorrhage or hydrocephalus on preoperative CT Head (p=0.007). Patients treated with SRS therapy were more likely to have residual AVM on long-term post-treatment angiogram (p=0.008). There were no statistically significant outcome differences between the surgery and SRS cohorts. Conclusion: Treatment of posterior fossa AVMs requires a tailored multimodality approach utilizing endovascular embolization and surgical resection to optimize total obliteration and should be used first if safely feasible. SRS can be utilized as salvage therapy for recurrent/residual or surgically inaccessible AVMs.