Comparative Efficacy and Safety of Coil Versus Onyx Embolization in Middle Meningeal Artery Embolization as an Adjunct to Burr Hole Drainage for Chronic Subdural Hematoma.
Liu C, Chen F, Lu P, Wang Y • Annali italiani di chirurgia • 2026
In the adjunctive treatment of cSDH with burr hole drainage, coils and Onyx liquid embolic agent demonstrate comparable short-term efficacy and overall safety, though coils were associated with shorter operative time and lower hospitalization costs.
Key Findings
Results
Hematoma volume absorption at 90 days postoperatively was not significantly different between the coil and Onyx groups.
This was the primary outcome of the study.
Post-matching analyses demonstrated 'no statistically significant differences between the two groups in hematoma absorption volume at 90 days postoperatively.'
Other imaging parameters were also comparable between groups.
Propensity score matching (PSM) was used to balance baseline characteristics, resulting in 66 patients per group.
Results
Clinical outcomes including modified Rankin Scale scores, recurrence rates, and reoperation rates were comparable between the coil and Onyx groups.
The proportions of patients with mRS scores of 0–2 were comparable between the groups.
Recurrence and reoperation rates did not differ significantly between groups after PSM.
Study follow-up period was 90 days postoperatively.
184 total patients were enrolled, with 66 in each group after PSM.
Results
Facial nerve palsy occurred exclusively in the Onyx group and not in the coil group.
Cases of facial nerve palsy were observed in the Onyx group, whereas 'no such complications were observed in the coil group.'
The overall incidence of serious adverse events (SAEs) was otherwise comparable between the two groups.
This represented a qualitative safety difference between the two embolic agents.
Facial nerve palsy is a known potential complication of liquid embolic agents due to their flow characteristics.
Results
The coil group had a significantly shorter operative time compared to the Onyx group.
The difference in operative time was statistically significant (p < 0.05).
Length of hospital stay did not differ significantly between the groups.
This finding was part of perioperative assessments comparing the two techniques.
Results
Hospitalization costs were significantly lower in the coil group compared to the Onyx group.
The difference in hospitalization costs was statistically significant (p < 0.05).
This represented a health economic advantage for coil embolization.
Length of hospital stay did not differ significantly between the two groups.
The study explicitly included health economic indicators as secondary outcomes.
Methods
This was a single-center retrospective cohort study of patients with chronic subdural hematoma who underwent burr hole drainage combined with middle meningeal artery embolization between April 2024 and October 2025.
A total of 184 patients were enrolled.
Patients were divided into a coil group and an Onyx group based on the embolic material used.
Propensity score matching was used to balance baseline characteristics, yielding 66 patients per group.
The study period spanned approximately 18 months at a single center.
What This Means
This research suggests that two different materials used to block blood flow in the middle meningeal artery — metal coils and a liquid agent called Onyx — produce similar results when used alongside a standard surgical drain procedure for chronic subdural hematoma (a type of blood collection on the brain's surface). The study followed 184 patients over 90 days after surgery and found that the amount of blood reabsorbed, patient functional outcomes, and rates of the blood collection coming back were not meaningfully different between the two groups.
However, the study did identify some practical differences between the two approaches. Coil embolization was faster to perform and cost less during hospitalization than Onyx embolization. Additionally, some patients who received Onyx developed facial nerve palsy (temporary or permanent weakness of facial muscles), a complication that was not seen in any patients treated with coils. This suggests that while both materials are broadly effective and safe, Onyx may carry a small additional risk of this specific complication, possibly because liquid agents can flow into unintended areas during the procedure.
This research matters because middle meningeal artery embolization is a relatively new and growing treatment approach for chronic subdural hematoma, and clinicians need guidance on which embolic materials to use. The findings suggest that coils may offer advantages in procedure efficiency, cost, and potentially in avoiding facial nerve complications, while achieving outcomes equivalent to Onyx. However, because this was a single-center retrospective study with a relatively short follow-up period, larger and longer studies will be needed to confirm these findings.
Liu C, Chen F, Lu P, Wang Y. (2026). Comparative Efficacy and Safety of Coil Versus Onyx Embolization in Middle Meningeal Artery Embolization as an Adjunct to Burr Hole Drainage for Chronic Subdural Hematoma.. Annali italiani di chirurgia. https://doi.org/10.62713/aic.4654