MAGIC-MT study is multi-center, prospective, randomized (1:1) controlled trial designed to show that additional MMA embolization with Onyx in patients with non-acute symptomatic subdural hematoma(SDH) results in reduced hematoma recurrence in surgically treated patients/ reduced hematoma progression in conservatively managed patients.

The objective of this study is to show that additional MMA embolization with Onyx in patients with non-acute symptomatic subdural hematoma(SDH) results in reduced hematoma recurrence in surgically treated patients/ reduced hematoma progression in conservatively managed patients.

Inclusion Criteria:

1. Patients with symptomatic non-acute SDH with mass effect (i.e., chronic or subacute SDH)

   1. Mass effect refers to a shift in midline structure or deformation of local cerebral cortex due to SDH.
   2. Symptomatic defined as neurological symptoms, such as headache, short-term cognitive dysfunction, language disorder or aphasia, gait instability, decreased muscle strength, sensory disturbances, epileptic seizure, etc.

2. Age ≥18 years;

3. Pre-morbid mRS score 2;

4. Informed Consent Form (ICF) signed by patient or guardian.

Exclusion Criteria:

1. Radiographic imaging indicating massive cerebral infarction with corresponding symptoms;
2. Required craniotomy or craniotomy with small bone flap to remove SDH;
3. Emergency SDH removal/drainage;
4. Bilateral SDH with unknown origin of symptoms;
5. Anatomical variations that may affect the safety of MMA embolization (e.g., prominent middle MMA-ophthalmic artery anastomosis);
6. Intractable coagulation dysfunction or abnormal platelet count and function (pre-operative International Normalized Ratio [INR] > 1.5 and/or platelet count < 80109/L);
7. Contraindications to cerebral angiography, such as allergy to iodinated contrast agents, renal insufficiency (GFR < 30 ml/min), etc.;
8. Computed tomography (CT) or magnetic resonance imaging (MRI) showing intracranial space-occupying lesions;
9. Pregnancy or planning to become pregnant;
10. Serious or fatal coexisting disease that may prevent improvement of conditions or completion of follow-up;
11. Life expectancy < 1 year;
12. Recent operation unrelated to this study or investigators believe that they will be at higher risks if antiplatelet and/or anticoagulant drugs are discontinued;
13. Inability to complete follow-up as required by the protocol;
14. Patients participating in other clinical trials;
15. Prior surgery or interventional therapy on target SDH;
16. Inability to complete MMA embolization before trepanation and drainage.