1186. Presentation and Multi-modality Treatment of Posterior Fossa Arteriovenous Malformations

Authors: Kevin Kwan, MD; Brooke Kennamer; George Klironomos, MD; Julia Schneider, BS; Andrew Kobets, MD; Jeffrey Katz, MD; David Chalif, MD; Amir Dehdasti, MD (Manhasset, NY)

Introduction: Posterior fossa arteriovenous malformations (AVMs) are relatively uncommon and among the most challenging lesions to treat in neurosurgery. We present multimodality treatment of forty-seven posterior fossa AVMs. Methods: A retrospective review was performed to identify all 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 exact 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 the patients who had surgery had evidence of residual AVM. The most common surgical complications 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). Conclusion: Treatment of posterior fossa AVMs requires a tailored multimodality approach utilizing endovascular embolization and surgical resection to optimize the chances for total obliteration and should be used first if safely feasible. SRS can be utilized as salvage therapy for recurrent/residual or surgically inaccessible AVMs.