Angiographic Grading of Liquid Embolic Penetration in Middle Meningeal Artery Embolization: A Novel Grading System for Predicting Chronic Subdural Hematoma Resolution

BACKGROUND AND PURPOSE: Middle meningeal artery (MMA) embolization is increasingly used to treat chronic subdural hematoma (cSDH) following surgical evacuation. However, no standardized system exists to assess angiographic embolization extent or its clinical impact. This study introduces a novel grading system for evaluating liquid embolic penetration and its association with outcomes. MATERIALS AND METHODS: Consecutive patients who underwent MMA embolization using n-butyl cyanoacrylate between 2019 and 2023 were included. Data were prospectively collected and retrospectively analyzed, including demographics, hematoma characteristics, and follow-up imaging up to 12 months. Embolization was graded on a 4-point angiographic scale: 1—proximal ligation, 2—branch penetration without midline reach, 3—penetration to midline, and 4—crossing midline. Postoperative CT was used to evaluate hematoma volume and recurrence. Linear and logistic regression analyses were performed to correlate angiographic grade with time to resolution and recurrence, with significance at P < .05. RESULTS: Seventy-three patients met the inclusion criteria. Embolization was grade 2 in 43.8%, grade 3 in 46.6%, and grade 4 in 5.5%. Complete cSDH resolution within 3 months occurred in 19% of patients, with a mean resolution time of 6.60 ± 4.07 months. Each grade increase correlated with a 1.61-month faster resolution (P = .048) and a significantly higher likelihood of 3-month resolution (OR: 4.86; 95% CI: 1.36–23.9; P = .027). CONCLUSIONS: Deeper liquid embolic penetration on angiography is associated with faster and more complete cSDH resolution. This novel grading scale may serve as a useful intraprocedural tool, pending further validation in larger prospective studies.