Balt’s Squid Receives Premarket Approval for Patients with Chronic Subdural Hematomas

In recent news, Balt Inc. announced that the FDA has granted premarket approval for the Squid liquid embolic agent for embolization of the middle meningeal artery as an adjunct to usual care in patients with large symptomatic chronic subdural hematomas. The approval was based on results from the prospective, randomized STEM trial (NCT04410146), which evaluated MMA embolization for cSDH and demonstrated a significant reduction in treatment failures in a large patient population.¹

The STEM trial, originally published in the New England Journal of Medicine in November of 2024, demonstrated that adjunctive embolization of the MMA with Squid significantly reduced treatment failure rates without increasing adverse events (AEs) in patients managed with either surgery or medical management.

In the primary efficacy analysis, a primary outcome event occurred in 19 of 120 patients (16%) in the embolization group versus 47 of 129 patients (36%) in the control group, corresponding to a 64% relative reduction in risk (odds ratio [OR], 0.36; 95% CI, 0.20–0.66; P = .001). These findings underscored the clinical benefit of embolization in lowering recurrence and treatment failure rates among patients with cSDH.²

“It was clear from the initial cases that Dr. Adam Arthur and I performed that middle meningeal artery embolization showed promise for these patients; however, high quality data were required to confirm the effectiveness and safety of the procedure and to ultimately generate a paradigm shift towards this minimally invasive treatment becoming the standard of care,” David Fiorella, MD, PhD, STEM trial principal Investigator and professor at the Stony Brook University Medical Center in Pennsylvania, said in a statement.¹ “I am very thankful that Balt’s leadership team aligned with this vision and took the bold step to support STEM, the very first prospective randomized trial assessing the effect of liquid embolics in patients with symptomatic cSDH.”

Squid is an ethyl vinyl alcohol (EVOH) copolymer in a dimethyl sulfoxide (DMSO) solvent used in embolization of blood vessels in vascular diseases. The EVOH based device also provides a wide range of viscosities (12, 18, and 34) and micronized tantalum. Originally approved for use in Europe in 2012, Squid is indicated for the embolization of the MMA as an adjunct to usual care treatment in patients with cSDH measuring 10 mm or greater in thickness in whom an intervention is deemed necessary as determined by a neurosurgeon.

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Having been approved for nearly a decade, Squid was tested against other available liquid embolic agents in a 2021 study published in Clinical Neuroradiology. In total, the trial tested 4 embolic agents as a treatment option for cerebral arteriovenous malformations (AVMs) and dural arteriovenous fistulas (DAVFs) and found that each treatment has its own potential advantages and disadvantages over each other. Overall, the study urged clinicians to choose the most appropriate embolic agent based on the specific material characteristics of the agent, related to the specific anatomical characteristics of the target pathology.³

REFERENCES
1. Balt’s Squid™ Liquid Embolic Receives FDA Approval for Adjunctive Treatment for Patients with Chronic Subdural Hematomas. Balt Inc. News Release. February 4, 2026. Accessed February 18, 2026. https://www.globenewswire.com/news-release/2026/02/04/3232016/0/en/Balt-s-Squid-Liquid-Embolic-Receives-FDA-Approval-for-Adjunctive-Treatment-for-Patients-with-Chronic-Subdural-Hematomas.html
2. Fiorella D, Monteith S, Hanel R, et al. Embolization of the Middle Meningeal Artery for Chronic Subdural Hematoma. New England Journal of Medicine. 2024; 392(9):855-864 doi: 10.1056/NEJMoa2409845
3. Vollherbst, D, Chapot, R, Bendszus, M, Möhlenbruch M. Glue, Onyx, Squid or PHIL? Liquid Embolic Agents for the Embolization of Cerebral Arteriovenous Malformations and Dural Arteriovenous Fistulas. Clin Neuroradiol. 2022;32:25–38. doi:org/10.1007/s00062-021-01066-6