EMMA-Can is a prospective randomized open-label, blinded end point (PROBE) study, that will assess the recurrence risk and safety of embolization of the middle meningeal (EMMA) when added to standard of care treatment (surgical drainage) of chronic subdural hematoma (CSDH) compared to surgical treatment alone.

All patients in clinical need of surgical drainage for the CSDH will be randomized in our study. Patients that present in the Emergency Department (ED) or neurosurgery clinic will be assessed for standard of care treatment options based on their presenting symptoms. Patients will then by screened for study eligibility based on the study inclusion and exclusion criteria. After screening and consenting patients will be randomized in to the control arm or interventional arm.

Patients randomized to the control arm will receive institutional standard of care treatment (surgical drainage) of the CSDH.

Patients randomized to the interventional arm will receive institutional standard of care treatment (surgical drainage) of the CSDH followed by EMMA, with Onyx and under a general anesthetic within 72 hours of surgical drainage.

All patients will be followed as per the institutional standard of the care. Any peri-procedural complications and change in clinical status will be recorded. The risk of recurrence at 90-days will be assessed in all patients.

Inclusion Criteria:

1. Premorbid Modified Rankin Scale of ≤2;
2. Patients with unilateral symptomatic primary or recurrent CSDH >10 mm in thickness on CT head undergoing surgical drainage;
3. CT Angiogram of head and neck which favors vascular access for EMMA and lacks dangerous anatomic variations;
4. Patients over 18 years of age; no upper age limit.

Exclusion Criteria:

1. If informed consent cannot be obtained from the patients or their substitute decision makers;
2. Patients with bilateral symptomatic CSDH;
3. CTA showing persistent communication between branches of middle meningeal artery and that of internal carotid arteries;
4. Contraindication to the embolization procedure such as severe renal dysfunction (eGFR<30), or pregnancy;
5. Life expectancy < 6 months;
6. Known allergy to Onyx;
7. Acute subdural hematoma with homogenous hyperdensity on CT scan;
8. Secondary CSDH that may likely be due to the underlying condition such as a vascular lesion, brain tumor, arachnoid cyst, spontaneous intracranial hypotension or prior craniotomy;
9. Patients needing treatment with 2 weeks of dexamethasone or tranexamic acid will be contraindicated in the study patients to avoid confounding.