A new low-viscosity EVOH liquid embolic — what sets it apart, and how it performs
Two complementary talks at LINNC Paris 2026 put Onyx 12 in the spotlight: a device and evidence update from Adam Arthur (CMO, Medtronic Neurovascular), and an early clinical experience from Jan Gralla (Inselspital, University of Bern). The shared message was clear ; Onyx 12 brings the familiar, controllable behaviour of the Onyx family to a lower-viscosity formulation built for distal reach.
What differentiates Onyx 12
Onyx 12 is the lowest-viscosity member of the Onyx EVOH line (alongside Onyx 18, 20 and 34), and its design targets the recurring trade-off of liquid embolization — penetration versus reflux control:
- Greater distal penetration without greater reflux. The lower viscosity reduces forward-flow resistance and pushes the agent further into the target network, while the plug-forming properties of Onyx 18 are preserved ; so reflux resistance is retained rather than sacrificed for reach.
- Excellent visibility. Onyx 12 remains highly radiopaque, letting the operator see exactly where the cast is forming, even in small vessels.
- Faster preparation. A 1-minute shake time delivers the same tantalum dispersion as the standard formulation, shortening set-up without compromising visibility.
These properties open a broad set of indications where reaching a distant target matters: cSDH / MMA embolization, bAVM, dAVF with a remote fistula point, tumour devascularization, and CSF venous fistula.
The hands-on verdict
Reporting independent early use, Jan Gralla described Onyx 12 as an agent that “does what it’s supposed to do,” with a brisk, continuous initial injection that behaves like NBCA, very good distal penetration, and good radiographic visibility.
His cases spanned a bilateral cSDH, a symptomatic residual cSDH on antiplatelet therapy, a recurrent Borden III dAVF fed by a residual MMA, and pre-operative devascularization of a hypervascular tumour followed by complete resection with limited blood loss.
The European early experience echoed this. From UKE Hamburg, Dr Maxim Bester reported better distal penetration than Onyx 18 with good reflux control and visibility he rated above Squid 12, while Dr Fabian Flottmann noted deep distal penetration with preserved proximal flow control. In the first bAVM case (Limoges, April 2026), Prof. Charbel Mounayer said he was positively surprised ; good contrast and penetration with reflux comparable to Onyx 18.
Takeaway
Onyx 12 extends a well-understood embolic platform into the low-viscosity space, with its headline being distal penetration without added reflux, fast preparation, and strong visibility. With MMAE in cSDH now backed by randomized evidence and guideline support, the agent arrives in a maturing field.
Jildaz Caroff
Hôpital Bicêtre,
Paris, France
Supported by Medtronic
