Chronic Subdural Hematomas (cSHD) are common, and due to cerebral compression, often result in neurological impairment and reduced consciousness. Surgery is typically performed once neurological symptoms develop. Recent studies suggest that arteries nourished by the middle meningeal artery (MMA) may be responsible for hematoma progression and that MMA embolization is clinically useful. There is less evidence, that embolization of MMA also may be a treatment option for individuals without surgical treatment. The investigators propose a multicentre study to investigate both potentials: (1) Assessment of efficacy of embolization after surgery to reduce recurrence and improve outcomes by conducting a randomized trial (randomization arms; Arms 1 and 2), (2) Assessment of embolization-alone efficacy when surgery is contraindicated or refused (embolization-only arm, Arms 3 and 4).

Evidence to support the benefit of MMA embolization remains limited and the risk-benefit balance remains unclear. Case series have shown that recurrence rates with embolization are much lower, and that embolization is generally very safe. Risks associated with neurointerventional procedures will be directly discussed with patients or their caretakers as part of the conventional consenting procedure. Risks include access site hematoma, radiation exposure, vascular injury, brain ischemia, death (theoretic and extremely unlikely) and typical risks associated with general or local anaesthesia. The potential efficacy of MMA embolization as a treatment therefore requires higher level evidence in the form of randomized control trials.

The benefit of the embolization is a substantial reduction in recurrence of cSDH, which has been reported to be as high 1 in 3-4 patients. Recurrence of cSDH can lead to additional surgery and complications.

First objective: Evaluate the recurrence rates of cSDH after combined surgical and MMA embolization treatments (Arm 2) versus surgery alone (Arms 1).

Second objective: The second objective is to evaluate the stability and regression of cSDH after for all the Arms of the study at follow-up.

Inclusion Criteria:

• Age: 18-100
• Consent possible
• cSDH located at the convexities
• Patients with symptomatic cSDH
• Patients with asymptomatic large chronic/subacute hematoma after 6 weeks of failed conservative treatment

Exclusion Criteria:

• Consent not possible
• Pregnancy
• Prisoner
• Angiography contraindication
• Patient for whom follow-up is problematic (e.g. distant residency, homeless …)
• Previous surgery for cSDH