Introduction/Purpose Non-Acute Subdural Hematoma (NASDH) is challenging to treat due to high recurrence rates ranging from 2-37%. Middle meningeal artery embolization (MMAe) is a minimally invasive procedure which improve outcomes in NASDH. This study evaluates clinical and radiographic characteristics of patients with NASDH undergoing MMAe when utilized upfront, prophylactically, or as a salvage modality after surgical evacuation.

Methods This prospective study followed patients undergoing MMAe for NASDH from 2016-2022. All patients were diagnosed with a NASDH on CT imaging and underwent MMAe by the lead Neurointerventionalist. Outcomes were assessed based on radiographic and clinical follow up within one-year follow-up. Primary outcome of NASDH recurrence following MMAe was defined as hematoma recurrence requiring surgical evacuation, repeat MMAe, or both within the one-year. Radiographic outcomes included SDH recurrence, reduction of hematoma width and midline shift, and collection density evaluation (mean Hounsfield Units) up to the longest follow-up. Subgroup analyses stratified outcomes by MMAe indication: upfront, salvage, or prophylactic. Oncologic, coagulopathic, and anticoagulant-antiplatelet (ACAP) patients were also assessed. Post-MMAe clinical outcomes were assessed by modified Rankin scale (mRS).

Results 236 NASDH patients underwent 294 MMAe. 115 (48.7%), 92 (39.0%), and 29 (12.3%) patients received upfront (previously untreated and nonoperative NASDH), prophylactic (MMAe following hematoma evacuation), and salvage (individuals with NASDH recurrence following a previous surgical evacuation) MMAe, respectively. Upfront MMAe was performed more frequently than prophylactic and salvage for patients with co-existing malignancy (29.6%, 12.0%, 20.7%; p < 0.01) and coagulopathy (17.4%, 4.3%, 10.3%; p = 0.01). Polyvinyl alcohol was preferred over onyx as embolic agent (94.1% vs 5.9%; p < 0.01). There were 16 (5.4%) recurrences after MMAe, of which 5 (1.7%) received a craniotomy, 7 (2.4%) received an MMA embolization, and 4 (1.3%) underwent both MMAe and surgical evacuation. Clinical outcomes did not differ between MMAe indications at longest follow-up. Statistically significant decreases in collection size and density were seen across all cohorts on follow-up. Subgroup analysis revealed decreased NASDH recurrence in oncologic, coagulopathic, and ACAP patients. Multivariate regression identified history of falls, coagulopathy, hematoma size, and male sex increased the likelihood of NASDH recurrence requiring repeat intervention following MMAe (p < 0.05); whereas, periprocedural SEPS and presence of subdural septation/membranes decreased the likelihood of recurrence requiring intervention (p < 0.05). Hematoma size of 4.63 mm or greater on initial presentation were 2.21 times more likely to recur and patients with cancer were 3 times more likely to have subdural hematoma recurrence.

Conclusions MMAe is a viable treatment for reducing recurrence and improving outcomes in patients with NASDH compared to historical controls and prevent the need for the first time or repeat surgical evacuation., noting beneficial radiographic and clinical outcomes when performed upfront, prophylactically, or as salvage treatment. This data reports one of the largest analyses of patients having undergone MMAe with clinical follow-up alongside measurements of collection sizes and density values before and after embolization. MMAe in high-risk coagulopathic, oncologic, and anticoagulated patients can reduce collection recurrence in special populations predisposed to increased hematoma formation and recurrence.

Disclosures J. Carnevale: None. S. Guadix: None. M. Wood: None. S. Sundararajan: None. N. Kharas: None. J. Goldberg: None. A. Ramos: None. J. Schwarz: None. S. Boddu: None. J. Knopman: None.