Abstract 411: Starting anticoagulation within 24 hours of primary Middle Meningeal artery embolization for chronic subdural hematoma (SDH) is safe and allows for chronic SDH resorption.

Introduction Middle Meningeal artery (MMA) embolization has emerged as an effective treatment for the resorption of chronic subdural hematoma (cSDH), by occluding the blood supply to the subdural hematoma membrane; thereby preventing leakage of blood into the subdural space. Limited data is available for initiating anticoagulation within 24 hours post primary MMA embolization and maintaining the anticoagulation treatment, with regards to its effect on the cSDH. Methods A prospective collection of patients requiring MMA embolization for cSDH was maintained from a single center between 2019 and 2023. Patients that received full strength anticoagulation within 24 hours of primary MMA embolization were included in this study. All patients were treated with 100‐300 micron embospheres for distal penetration. Some patients received ONYX embolization at the proximal portion of the Middle Meningeal artery. Alternatively, some patients had the proximal portion of the MMA occluded using coils. A successful outcome is defined as complete resolution of the subdural hematoma and/or trace residual (less than or equal to 4 mm) between 1 and 6 months post treatment, while maintaining medication compliance to the anticoagulation treatment. Subdural hematoma expansion, need for surgical treatment (burr hole and/or craniotomy) and mortality were documented. Results 39 out of 148 patients (26%) were treated with primary MMA embolization (25 male). Anticoagulation was required for atrial fibrillation (36 patients) and DVT/PE (3 patients). All patients that followed up in clinic confirmed anticoagulation medication compliance. Complete subdural hematoma resolution was seen in 17 (43.5%) patients (mean age 74). 7 patients (18%) demonstrated trace residual (less than or equal to 4 mm) subdural hematoma on the three month follow up CT scan, but they all did not have a six month follow up CT scan. Burr hole evacuation was required in 1 patient (2.5%) due to hematoma expansion. There were no patient deaths or neurologic deficits related to subdural hematoma expansion on anticoagulation following embolization. Following the initial embolization, 8 patients (22%) demonstrated reduced/stable subdural hematoma on their approximate one month follow up imaging, but they had incomplete follow up imaging. Following the initial embolization, 6 patients (15%) have no follow up imaging. The COVID pandemic created an environment that limited access to the hospital for many patients. Conclusion Initiation of anticoagulation within 24 hours of primary MMA embolization is safe and can lead to complete resorption of the chronic subdural hematoma. Further studies are required to identify patient characteristics that may lead to hematoma expansion following embolization and the initiation of anticoagulation.