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Introduction Embolization of the middle meningeal artery (MMA) with liquid embolic materials may improve rates of chronic subdural hematoma (cSDH) resolution and reduce reoperation rates. At present, the efficacy of non-liquid embolic approaches remains incompletely characterized. The Coil and Particle Embolization (CAPE) study is a prospective single-arm trial evaluating outcomes in patients with cSDH treated with coil and polyvinyl alcohol (PVA) particle embolization.Methods CAPE is a prospective single-arm trial enrolling patients with cSDH at three centers across the Greater Houston area. Enrollment began in September 2025 and is ongoing. Patients were eligible if the hematoma consisted of ≥50% chronic and/or subacute components, irrespective of prior surgical evacuation. The intervention consists of particle embolization (100–300 µm EmboSpheres) when feasible, and all patients undergo coil embolization with Kaneka coils. The primary composite outcome mirrors the STEM trial outcome and includes recurrent or residual cSDH (>10 mm), reoperation or surgical rescue, and major neurologic events (disabling stroke, myocardial infarction, or neurologic death) within 6 months. The primary analysis will compare outcomes with the STEM trial control arm as a historical comparator. Secondary analyses will examine differences between surgical and non-surgical subgroups, the effects of hematoma composition and thickness, and associations with the number of coils used.Results A total of 52 patients with 70 hematomas have been enrolled thus far (table 1), with a median age of 72 years (IQR, 68–79). Most patients were male (n=38, 73.1%) and non-Hispanic/Latino (n=33, 63.5%). Anticoagulation use was present in 36.5%. Hematomas were distributed as left-sided (52.9%) and right-sided (47.1%), while 18 patients (34.6%) presented with bilateral cSDH. Despite selection for chronic/subacute hematomas, 29 (41.4%) demonstrated an acute sub-component. The mean number of coils used was 3.30 (SD 1.39) per hematoma. Successful embolization was achieved in all treated MMAs, which was graded as complete (PACE 0) in 92.3% of cases, with trace residual filling of frontal and/or temporal branches (PACE 1) in 7.7%, and no major peri-procedural complications were observed. Clinical follow-up is ongoing, and outcome data will undergo planned interim analysis by the time of the SNIS meeting.Conclusion The prospective CAPE trial evaluates safety and efficacy of coil and particle MMA embolization for cSDH, demonstrating high technical success and an absence of major peri-procedural complications to date. By the time of the conference, we anticipate reaching 80% of target enrollment, with primary endpoint data available for 50% of the target cohort.Disclosures J. Gomez-Farias: None. J. Samaha: None. B. Kfoury: None. M. Khalid: None. F. Kanakhara: None. M. Le Ngoc: None. H. Azeem: None. C. Vilaseca-Guzman: None. H. Zeineddine: None. S. Sheth: None. R. Regenhardt: None.