Weighing up particles, EVOH-based liquid agents and glues in MMA embolisation

With the technique of middle meningeal artery embolisation (MMAe) presently coming of age in chronic subdural haematoma (cSDH) management, Franziska Dorn (Bonn, Germany) outlines how three of the main materials used during these procedures—microparticles, ethylene-vinyl alcohol (EVOH)-based liquid embolic agents and cyanoacrylate glues—appear to stack up.

Recent randomised controlled trials have confirmed that MMAe can reduce recurrence and reoperation rates compared with standard care alone in patients with cSDH.^1–3 With MMAe now incorporated into treatment algorithms across most neurointerventional centres, attention is turning to a practical question every interventionist faces: which embolic agent achieves the most durable, safest occlusion?

Particles: familiar but limited

Polyvinyl alcohol (PVA) particles and trisacryl microspheres were the first materials adopted for MMAe. They are widely available, cheap and technically straightforward, and early series demonstrated reduced recurrence compared with historical controls.⁴ Yet, particle embolisation generally results in proximal occlusion rather than true capillary-level devascularisation. Recanalisation and collateral regrowth are plausible explanations for the somewhat higher recurrence rates reported in particle-only cohorts.⁵

The EMPROTECT study found no positive treatment effect for MMAe with particle embolisation.⁶ The authors used relatively large particles (300–500µm) and explained their choice by citing a favourable safety profile while acknowledging the risk of insufficient distal penetration. The impact of particle size and the use of spherical versus non-spherical particles on therapeutic success may be the subject of future research.

EVOH-based liquid embolics: evidence exists

The first three randomised controlled trials (RCTs) that provided proof of the benefit of MMAe in patients with cSDH all used non-adhesive, EVOH-based embolic agents such as EMBOLISE and MAGIC-MT (Onyx [Medtronic]), and STEM (Squid [Balt]).

These EVOH or co-polymer systems solidify slowly as dimethyl sulfoxide (DMSO) diffuses away, allowing the operator to perform a ‘plug-and-push’ injection that promotes gradual distal penetration under fluoroscopy.⁷ The controllable injection profile—cohesive rather than adhesive in nature—and radiopacity are a clear advantage of EVOH-based embolic agents.

However, both Onyx and Squid require flushing of the microcatheter with DMSO prior to embolisation, which can cause significant pain in awake patients and harbours the risk for trigeminocardiac reflex and, potentially, cardiovascular instability. Most neurointerventionists therefore prefer embolisation with EVOH-based agents under general anaesthesia.

Cyanoacrylate glues: old material, new momentum?

Cyanoacrylates, such as n-butyl cyanoacrylate (n-BCA; Glubran) and histoacryl, have played an important part in the neurointerventional treatment of vascular malformations for many years. These agents polymerise instantly when in contact with blood, creating a robust adhesive cast that permanently occludes the targeted branch.

Preliminary results from the randomised MEMBRANE study were presented at last year’s Society of Vascular and Interventional Neurology (SVIN) annual meeting (20–22 November, San Diego, USA) and also at the 2025 European Society of Minimally Invasive Neurological Therapy (ESMINT) annual congress (3–5 September, Marseille, France), and proved superiority of MMAe using n-BCA (Trufill [Johnson & Johnson MedTech]) when compared to standard treatment alone, especially in the surgical group of patients.⁸ However, the use of glue-like embolics requires high neurointerventional expertise due to the risk of reflux, catheter entrapment, and unpredictable polymerisation.

To alleviate some of the challenges of n-BCA, n-hexyl cyanoacrylate (n-HCA; Magic Glue [Balt]) monomers have been introduced. N-HCA has additional alkyl chains, which make it less adhesive, thus allowing for prolonged embolisation time and a decreased risk of catheter entrapment due to the slower polymerisation. This characteristic potentially allows for a more effective and ultimately safer embolisation procedure. Notably, as with any cyanoacrylate glue, Magic Glue does not require microcatheter flushing with DMSO prior to injection, but it has a 5–10% glucose solution, therefore limiting the risk for trigeminocardiac complications and providing a painless procedure that can be performed without general anaesthesia. Our recently published multicentric series including 58 MMAe procedures using Magic Glue indicates that it is a safe and effective alternative to established liquid embolics.⁹

Comparative outcomes

Systematic reviews encompassing thousands of patients now confirm that MMAe significantly reduces recurrence and need for reoperation compared with surgery or conservative management alone.^{10, 11} When stratified by material, liquid embolics—non-adhesive and adhesive—tend to show slightly lower recurrence rates than particles.^5,7

MMAe has transformed the management landscape for cSDH. The growing literature demonstrates that liquid embolics—both non-adhesive polymers and adhesive glues alike—achieve deeper penetration and more durable devascularisation than particulate agents. But, for now, the optimal embolic remains the one that the operator handles safely and confidently.

References:

1. Davies J M, Knopman J, Mokin M et al. Adjunctive Middle Meningeal Artery Embolization for Subdural Hematoma. N Engl J Med. 2024; 391: 1890–900. DOI: 10.1056/NEJMoa2313472.
2. Liu J, Ni W, Zuo Q et al. Middle Meningeal Artery Embolization for Nonacute Subdural Hematoma. N Engl J Med. 2024; 391: 1901–12. DOI: 10.1056/NEJMoa2401201.
3. Fiorella D, Monteith S J, Hanel R et al. Embolization of the Middle Meningeal Artery for Chronic Subdural Hematoma. N Engl J Med. 2025; 392: 855–64. DOI: 10.1056/NEJMoa2409845.
4. Link T W, Boddu S, Paine SM et al. Middle Meningeal Artery Embolization for Chronic Subdural Hematoma: A Series of 60 Cases. Neurosurgery. 2019; 85(6): 801–7. DOI: 10.1093/neuros/nyy521. PMID: 30418606.
5. Kan P, Maragkos G A, Srivatsan A et al. Middle Meningeal Artery Embolization for Chronic Subdural Hematoma: A Multi-Center Experience of 154 Consecutive Embolizations. Neurosurgery. 2021; 88(2): 268–77. DOI: 10.1093/neuros/nyaa379. PMID: 33026434.
6. Shotar E, Mathon B, Salle H et al. Meningeal Embolization for Preventing Chronic Subdural Hematoma Recurrence After Surgery: The EMPROTECT Randomized Clinical Trial. JAMA. 2025; 334(2): 127–35. DOI: 10.1001/jama.2025.7583. PMID: 40471557. PMCID: PMC12142473.
7. Mortezaei A, Al-Saidi N, Ghorbi L et al. Comparative analysis of Onyx, squid, and n-BCA in middle meningeal artery embolization for chronic subdural hematoma: a meta-analysis of randomized controlled trials. Neuroradiology. 2025; 67(6): 1557–66. DOI: 10.1007/s00234-025-03651-9. PMID: 40392287.
8. Rai A (2024). MEMBRANE trial [podium presentation]. SVIN annual meeting: San Diego, USA. https://neuronewsinternational.com/membrane-becomes-latest-rct-to-demonstrate-mma-embolisations-benefits-in-csdh-treatment/.
9. Lehnen N C, Böhnert D, Dracini D et al. N-hexyl cyanoacrylate (Magic Glue) for middle meningeal artery embolization: a retrospective multicenter analysis. J Neurointerv Surg. 2025: jnis-2025-023862. DOI: 10.1136/jnis-2025-023862. Online ahead of print. PMID: 40750347.
10. Levitt M R, Hirsch J A, Chen M. Middle meningeal artery embolization for chronic subdural hematoma: an effective treatment with a bright future. J Neurointerv Surg. 2024; 16(4): 329–30. DOI: 10.1136/jnis-2024-021602. PMID: 38365442.
11. Gajjar A A, Naqvi A, Chen J Y et al. 2024 middle meningeal artery embolization trials: A comprehensive review of past, recent, and ongoing trials. Interv Neuroradiol. 2025: 15910199251329970. DOI: 10.1177/15910199251329970. Online ahead of print. PMID: 40183372. PMCID: PMC11977622.

Franziska Dorn is director of the Neurointervention Section and deputy director of the Department of Neuroradiology at University Hospital Bonn in Bonn, Germany. She is also a founding member of the ‘Work and Family’ taskforce group of the German Society of Neuroradiology (DGNR).

DISCLOSURES: The author declared no relevant disclosures.