1263 Internal Hematoma Architecture Predicts Subdural Hematoma Responsiveness to Upfront Middle Meningeal Artery Embolization

INTRODUCTION: Subdural hematoma (SDH) is quickly becoming the most common neurosurgical pathology due to the aging population. Middle meningeal artery embolization (MMAE) has recently emerged as an effective adjunct to surgical SDH evacuation by decreasing recurrence risk. MMAE has also shown promise as a standalone SDH intervention, but clinical and radiographic predictors of successful MMAE remain ill-defined. METHODS: Retrospective review from 2020–2023 at a high-volume center identified all MMAE cases performed as primary SDH treatment. Subacute, chronic, or mixed density collections with less than a 50% acute component and minimal associated neurological symptoms were eligible. Cases were classified by hematoma internal architecture as homogeneous, separated, laminar, or trabecular (using the Nakaguchi classification). SDH maximal thickness was assessed on all follow-up imaging, and any SDH recurrences or expansions requiring surgical evacuation were denoted as treatment failures. RESULTS: 164 upfront MMAE cases were reviewed with a mean follow-up of 7.1 months. Most cases were in male patients (75.0%), and mean age was 73.2 years. The cases with laminar and trabecular collections were slightly larger than those with homogeneous and separated collections (16.2mm vs. 14.2mm, p=0.008*), but other baseline characteristics were similar. The overall MMAE failure rate was 6.7% with a 4.9% periprocedural complication rate. The MMAE failure rate was significantly lower in the laminar and trabecular subgroup (1.2%) compared to the homogeneous and separated subgroup (12.4%) (p=0.005*). Homogeneous and separated internal hematoma architecture was the only predictor of MMAE failure in multivariate analysis (OR 11.6, p=0.021*) and was also associated with delayed SDH resorption (Two-way ANOVA: F=4.8, p=0.0025*). CONCLUSIONS: Upfront MMAE is an effective, safe, and durable treatment for non-acute SDH, and is especially effective for hematomas with more membranous internal architecture.