Embolic Agents for Middle Meningeal Artery Embolization in Chronic Subdural Hematoma: a Systematic Review and Comparative Pooled Analysis.

PURPOSE: Middle meningeal artery (MMA) embolization has emerged as a promising alternative or supplement to surgery for chronic subdural hematoma (cSDH). However, the effectiveness of different embolic agents remains unclear.

METHODS

We systematically reviewed 41 studies published up to September 2025, including 8 meta-analyses, 1 scoping review, and 32 clinical cohorts or series. Embolic agents evaluated included liquid agents (Onyx, Squid, n‑BCA), particulates (polyvinyl alcohol [PVA], microspheres), and coils. The primary endpoint was treatment failure, defined as symptomatic or radiological recurrence of cSDH requiring repeat intervention (repeat MMA embolization or surgical rescue); secondary outcomes included complications, mortality, and functional outcomes.

RESULTS

No embolic agent demonstrated consistent superiority in randomized trials, meta-analyses, or observational cohorts. Pooled recurrence rates were lowest with n‑BCA (0.8%), followed by Squid (3.6%), Onyx (4.4%), PVA particles (7.3%), and coils (9.0%). Although pooled recurrence appeared lowest with n‑BCA and highest with coils, most randomized and observational comparative studies did not detect statistically significant differences between embolic agents. Major complications were infrequent (≈1-3%) and similar across agents. Liquid embolics had significantly higher costs than PVA particles but did not lead to improved functional outcomes.

CONCLUSION

MMA embolization is a safe and effective treatment for cSDH. Outcomes are generally similar across different embolic agents, and selection should be based on anatomical factors, operator expertise, and resource availability rather than expectations of agent-specific effectiveness.