due to reason 3 in the protocol- any new information becomes available during the trial that necessitates stopping the trial. New information became available with device no longer being investigational.

Endovascular middle meningeal artery (MMA) embolization is an emerging treatment for chronic subdural hematoma (cSDH). There is preliminary data to suggest that this minimally invasive therapy may be more efficacious and equally as safe compared to conventional, more invasive surgery. This study seeks to assess the safety and efficacy of middle meningeal artery embolization for chronic subdural hematoma as an adjunct to standard treatments, which include medical management and surgical evacuation.

This study seeks to assess the safety and efficacy of middle meningeal artery embolization for chronic subdural hematoma in addition to standard treatments, which include close observation and surgical evacuation. Middle meningeal artery embolization has emerged recently as a minimally invasive and successful method of preventing re-accumulation of subdural hematoma, particularly for patients that are not obvious surgical candidates or those with recurrent or refractory hematomas. The outcomes of these two groups of patients who undergo middle meningeal artery embolization will be compared to matched historical controls.

Middle meningeal artery embolization is a minimally invasive angiography procedure completed with use of fluoroscopy. Access is obtained through the femoral or radial artery and a catheter is advanced to the MMA. Polyvinyl alcohol particles are then injected to seal off this portion of the artery and prevent any further blood flow into the subdural hematoma. Hemostasis is obtained at the access site and the patient is observed for 24-48 hours on a neurological care unit before discharge.

A head CT, NIHSS, and modified Rankin Score will be repeated on the following schedule: • Pre-Procedure

• 24 hours post procedure
• 7-10 days post procedure
• 30 days post procedure
• 90 days post procedure

Patients with chronic subdural hematoma undergo CT scans and neurologic assessments on hospital admission, as well as follow up CT scans and neurologic assessments to assess for any change in neurologic status or hematoma size. This study utilizes a standard of care follow up schedule to avoid exposing participants to extra radiation. Participants will be followed for study related purposes for 90 days.

Inclusion Criteria:

• Patients 18 years or older undergoing treatment for a new diagnosis of chronic subdural hematoma (cSDH) or
• Patients 18 year or older who have undergone surgical evacuation of a subdural hematoma and have a significant residual hematoma status post-surgery or who develop a recurrent subdural hematoma.

and

• Minimal symptoms such as headache, altered mental status, or mild neurological deficit only
• Ability to understand and sign written informed consent by patient or LAR

Exclusion Criteria:

• Significant midline shift and/or neurologic symptoms requiring urgent decompression.
• Common carotid stenosis of over 50%.
• Significant contraindication to angiography (eg. kidney failure, difficult anatomy).
• SDH related to underlying condition
• Acute SDH

number of participants reflects population with diagnosis