The SQUID Trial for the Embolization of the Middle Meningeal Artery for Treatment of Chronic Subdural Hematoma (STEM)

Inclusion Criteria: 1. Male or female Subject whose age is ≥ 30 at the time of consent 2. Pre-morbid mRS (Modified Rankin Scale) 0-1 within the previous 12 months 3. cSDH measures ≥ 10 mm in greatest thickness 4. cSDH exerts mass effect upon the subjacent brain, as indicated by local cortical flattening or midline shift 5. Imaging characteristics indicative of chronicity (≥ 50% of the volume of the collection should be isodense or hypodense to normal cortical gray matter on Computed Tomography (CT)) 6. Subject presents with one or more of the following neurological symptoms: headache; cognitive decline; speech difficulty or aphasia; gait impairment or imbalance; focal neurological deficit (weakness, paresthesia or sensory deficit involving of one or more extremities or facial droop); and/or seizure 7. Subject, or his/her legally authorized representative, understands the nature of the procedure, consents to participation in the study and provides a signed Informed Consent Form 8. Female Subjects of child-bearing potential must be able to provide a current negative urine pregnancy test and agree to an appropriate method of contraception throughout the trial 9. Subject is able and willing to return to the investigational site for all follow-up visits (e.g., 30-day, 90-day, 180-day and 1-year), as required per protocol Exclusion Criteria: 1. Subject with prior ipsilateral craniotomy or burr hole evacuation of cSDH 2. Subject with prior Embolization of either MMA 3. Subject requires (in the opinion of the treating surgeon) a full or mini craniotomy 4. Subject with urgent or emergent (within 1 hour of assessment) subdural hematoma evacuation needed 5. Subject with a cSDH with a focal location (confined to the frontal or temporal base or the inter-hemispheric space without cerebral convexity involvement) 6. cSDH developed due to underlying condition such as a vascular lesion, brain tumor, arachnoid cyst, spontaneous intracranial hypotension or secondary to a previous craniotomy 7. Life expectancy of \<1 year 8. Subject who presents with an intracranial mass other than subdural hematoma 9. Subject who presents with a meningioma with mass effect and/or ≥1 cm or currently undergoing radiation therapy for carcinoma or sarcoma of the head or neck region 10. Subject with serum creatinine level \> 3.0 mg/dL at time of enrollment (this will restrict the use of contrast) and not on dialysis 11. Subject with significant liver function impairment at the time of enrollment 12. Subject with a life-threatening allergy to radiographic contrast (unless treatment for allergy is tolerated or can be managed medically) 13. Subject who is currently enrolled in another investigational study protocol that could potentially confound the current study endpoints