The CHALLENGER Registry

* Age 18-98 years inclusively * Per CT of the head, (one of the following): * Unilateral convexity cSDH measuring at least 10 mm in thickness OR * Bilateral cSDH if only one side is considered for treatment and the contralateral side is asymptomatic and \< 5 mm in thickness. * cSDH at least 2/3 isodense or hypodense, verified on axial CT slice used to measure the thickness of the qualifying cSDH * Qualifying baseline head CT performed within the 14 days prior to treatment * Patient or legally authorized representative agrees to be participated in the study and provides written informed consent and Health Insurance Portability and Accountability Act (HIPAA) authorization Exclusion Criteria: * Secondary cause apart from trauma for the qualifying SDH, such as an underlying vascular abnormality or tumor * Bilateral cSDH with unknown origin of symptoms * Participants who underwent prior embolization of either MMA * Tentorial or interhemispheric SDH * mRS \>4 * On tranexamic acid * Intractable coagulation dysfunction or abnormal platelet count and function (pre-operative International Normalized Ratio \[INR\] \> 1.5 and/or platelet count \< 80109/L) * Anatomical variations that may affect the safety of MMA embolization (e.g., prominent middle MMA ophthalmic artery anastomosis) * Known contraindications to angiography * Known intolerance to occlusion procedures * Known vascular anatomy (small artery size) or blood flow (high vascular resistance peripheral to the feeding arter…