Middle meningeal artery embolization for chronic subdural hematoma: the role of timing and baseline hematoma volume

Background Middle meningeal artery embolization (MMAE) has shown efficacy for chronic subdural hematoma (cSDH), but optimal patient selection and timing (pre-, post-surgical, or standalone) remain unclear. This study evaluated the impact of volume, and embolization timing on outcomes at discharge and follow-up. Methods The study included 135 patients undergoing MMAE; only those with complete radiological data were analyzed. To reduce baseline clinical bias, patients were stratified into quartiles (Q) based on preoperative hematoma volume. Changes in functional status were assessed by calculating the difference in modified Rankin Scale (mRS) score between admission and discharge (ΔmRS a➝d ), as well as between admission and follow-up (ΔmRS a➝f ). The entire cohort was divided into three groups based on the timing of MMAE: pre-surgical, post-surgical and standalone. Results At admission, mRS distribution differed across quartiles ( p = 0.005), with better functional status more common in Q1 and higher mRS (≥ 3) increasing in larger volumes. At discharge, outcomes varied by embolization timing ( p < 0.001). Stand-alone treatment was associated with greater clinical stability, especially in Q1, while improvement increased with hematoma volume in the pre-surgical group. The post-surgical group showed a milder pattern of severity compared to the pre-surgical group. The same trends were observed at follow-up. On multivariable analysis, admission mRS was the strongest predictor of poor outcome (mRS ≥ 3) (OR 6.209, p < 0.001), with age also significant (OR 1.078, p = 0.027). Preoperative hematoma volume was the only independent predictor of reoperation (OR 1.017, p = 0.017). Conclusion Discharge outcome was mainly driven by admission mRS and age, while preoperative hematoma volume was associated with reoperation risk. In patients with lower hematoma burden (Q1-Q2), stand-alone MMAE showed greater early functional stability than pre- or post-surgical strategies.