The purpose of this study is to evaluate the safety and efficacy of embolization of the middle meningeal artery (MMA) using the NeoCast Embolic System for treatment of symptomatic subacute or chronic subdural hematoma (SDH) adjunctive to surgery.

This is a prospective, multi-center, randomized, controlled, single-blind pivotal trial to evaluate the safety and effectiveness of the NeoCast Embolic System in embolization of the middle meningeal artery (MMA) in surgically treated patients with symptomatic subacute or chronic SDH. Three hundred sixty participants will be randomized in a 2:1 ratio to be embolized with either the Arsenal Medical NeoCast Embolic System or Onyx LES, an FDA-approved commercial embolic. The Primary Effectiveness Endpoint will be measured at the 90-day timepoint post-treatment. Participants will be followed through 180 days.

Inclusion Criteria:

• Participant whose age is ≥ 18 and ≤ 90 years;
• Pre-morbid mRS ≤ 2;
• Confirmed diagnosis of subacute or chronic subdural hematoma that measures ≥10 mm in greatest thickness;
• Participant presents with one or more of the following corroborating neurological symptoms: headache; cognitive decline; speech difficulty; gait impairment or imbalance; focal neurological deficit; and/or seizure, within the last 30 days;
• Participant is planned for middle meningeal artery embolization within ±7 days of surgical evacuation of hematoma via burr hole or craniotomy;
• Participant or Legally Authorized Representative/Person Responsible for consenting on their behalf understands the nature of the procedure, consents to participation in the study and provides a signed informed consent form;
• Participant (woman of child-bearing potential) with a current negative pregnancy test who has agreed to an appropriate method of contraception throughout the trial;
• Participant is willing to return to the investigational site for follow-up visits.

Exclusion Criteria:

• Diagnosed with acute SDH
• Participant with prior embolization of either MMA
• Participant with urgent or emergent (within 1 hour of assessment) subdural hematoma evacuation needed
• Participant with bilateral SDH where both sides require surgery or contralateral SDH >5mm in greatest thickness
• Participant identified with potentially dangerous anatomic variations leading to increased procedural risk, risk of incomplete embolization, or unsafe access for MMA embolization (i.e., MMA originating from ophthalmic artery)
• Participant who presents with a meningioma ≥1 cm or < 1 cm with mass effect
• Subjects with conditions placing them at high-risk for ischemic stroke who cannot be taken off anticoagulants for at least 7 days post-surgery
• Participant currently undergoing radiation therapy for carcinoma or sarcomas of the head or neck region
• SDH developed due to underlying condition or structure pathology (e.g., dural AV fistula, AVM, tumor, arachnoid cyst, ventriculoperitoneal shunt, spontaneous intracranial hypotension or previous craniotomy)
• Presumed microbial superinfection
• Participant who is breastfeeding
• Participant with life expectancy of <1 year
• Participants with acute renal impairment that the investigator assesses could be at risk for contrast induced nephropathy
• Participant with a life-threatening allergy to radiographic contrast (unless treatment for allergy is tolerated or can be managed medically)
• Participant is allergic to any of the materials used in the NeoCast device or the Onyx LES commercial embolic device
• Participant who is currently participating or planning to participate within 6 months in another clinical research study

Independent Imaging Core Lab