Middle meningeal artery embolization as a surgical adjunct for non-acute subdural hematoma: real world outcomes and treatment effect heterogeneity

Background Middle meningeal artery embolization (MMAE) is a promising treatment for non-acute subdural hematoma (NASDH), but trial evidence is limited by heterogeneity and open label design bias. This study aims to assess the real world effectiveness of MMAE as an adjunct to surgery and to explore sources of treatment effect heterogeneity. Methods This was a retrospective cohort study of the Nationwide Readmissions Database (2016–22). Adults who underwent NASDH surgery were included and divided into two groups: surgery with MMAEand surgery only groups. Propensity score matching (PSM) balanced patient characteristics. The primary outcome was treatment failure (subdural hematoma readmission, repeat surgery, or death). The secondary outcome was surgical rescue. Cox proportional hazards models compared outcomes within 180 days. Interaction testing identified sources of treatment effect heterogeneity. Results Of 31444 included NASDH patients, 1544 underwent surgery with MMAE. After PSM, 1511 patients had surgery with MMAEand 4394 had surgery only. Surgery with MMAE was not associated with different rates of treatment failure (HR 0.80; 95% CI 0.56 to 1.13; P=0.20) or surgical rescue (HR 0.67; 95% CI 0.41 to 1.07; P=0.09). Interaction analyses revealed that surgical modality significantly modulated MMAE’s association risk of treatment failure (P interaction <0.001). Among patients treated with percutaneous drainage (Burr hole or twist drill trephination), surgery with MMAE was associated with a significantly lower risk of treatment failure (HR 0.42; 95% CI 0.25 to 0.71; P=0.001) and surgical rescue (HR 0.50; 95% CI 0.27 to 0.91; P=0.023). Surgery with MMAE was not associated with treatment benefit among patients who underwent open evacuation. Discussion For NASDH patients requiring surgery, MMAE was significantly associated with superior outcomes as an adjunct to percutaneous drainage, but not as an adjunct to open evacuation.