Management of CSDH With or Without EMMA- a Randomized Control Trial

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.