Orbital reconstruction and volume in the correction of proptosis after resection of spheno-orbital meningiomas

OBJECTIVE The objective of this study was to evaluate the effect of reconstruction and orbital volume on the reduction of proptosis in patients undergoing resection for spheno-orbital meningiomas. Additionally, potential predictors of optimal proptosis reduction after surgery were evaluated. METHODS Patients with spheno-orbital meningiomas who underwent resection at the authors' institution between 2005 and 2020 were evaluated retrospectively. The exophthalmos index (EI) was measured on pre- and postoperative imaging to quantify proptosis and calculate the primary outcome measure of proptosis reduction. Patients were excluded if they had no preoperative proptosis (i.e., EI < 1.1), prior resection, or insufficient imaging available for analysis. Clinical and surgical characteristics were collected, including sex, extent of resection, WHO grade, and rigid orbital reconstruction, and assessed as predictors of greater proptosis reduction. Additionally, orbital volumes of the affected and contralateral orbits were measured to correlate postoperative orbital volumes with proptosis reduction. RESULTS Thirty-three patients, with a mean age of 53 years, met inclusion criteria. The majority of the patients were female (23, 69.7%), and most tumors were classified as WHO grade 1 (29, 87.9%). Six patients (18.2%) underwent rigid orbital reconstruction. The mean EI across all patients decreased from 1.36 +/- 0.18 to 1.19 +/- 0.15 (p < 0.001). Patients who underwent reconstruction had on average a 76.4% greater reduction in the EI (p = 0.036) and a 9.1 times higher odds of achieving a normal EI (< 1.1) compared with those who did not receive reconstruction (OR 9.1, p = 0.025). Additionally, patients without residual hyperostotic bone compressing the orbit had a 2.16 times greater reduction in EI (p = 0.039). A linear relationship between orbital volume ratios (affected/unaffected orbit) and proptosis reduction was observed (p = 0.029, r = 0.529), including at ratios > 1.0. This suggests that greater orbital volumes postoperatively correlated with greater reductions in proptosis. CONCLUSIONS Three factors were identified that optimize proptosis correction. First, all abnormal bone compressing the orbital contents must be removed completely. Second, rigid orbital reconstruction leads to improved proptosis correction, possibly by preventing frontal lobe and dural reconstruction from descending onto the compressed orbit. Third, aiming for an orbital volume slightly larger than the contralateral normal side leads to improved proptosis correction.