Does the volume of Onyx injected influence outcomes after middle meningeal artery embolization for subdural hematoma?

Recent literature has highlighted the efficacy of liquid embolic agents like Onyx for middle meningeal artery (MMA) embolization of subdural hematoma (SDH). Our study aims to assess whether the volume of Onyx injected affects outcomes in patients undergoing MMA embolization for SDH.

This was a retrospective study of patients who underwent MMA embolization using Onyx for SDH at a single institution between March 2019- December 2024. Patients who underwent embolization using particles were excluded. Patients were dichotomized into two groups (≥0.7 ml or <0.7 ml) based on the 75th percentile of median volume of Onyx injected. The primary outcome of interest was embolization failure, defined as increase in hematoma thickness or need for surgical evacuation. The secondary outcome of interest was extended length of stay (eLOS), defined as LOS above the 75th percentile of the median.

A total of 123 MMA embolization procedures were included. The mean age of the cohort was 71.7 ± 13.5 years, and 26 % (n = 32) were female. 70.7 % of patients (n = 87) received a lower volume (<0.7 ml) of Onyx. Volume of Onyx was not associated with embolization failure or eLOS. Female gender (OR: 0.24, 95 % CI: 0.06-0.89, P = 0.034) was associated with lower odds of eLOS, while baseline functional dependence was associated with higher odds of eLOS (OR: 6.34, 95 % CI: 2.24-17.97, P < 0.001).

The volume of Onyx injected does not predict embolization failure or eLOS after MMA embolization for SDH. Future research could help validate our preliminary findings through prospective multicenter studies.