Orbital Expansion in Cranial Vault After Minimally Invasive Extradural Transorbital Decompression for Thyroid Orbitopathy

Purpose: To test the hypothesis that the orbit expands in the cranial vault after wide dural exposure after minimally invasive extradural transorbital decompression for thyroid eye disease. Methods: A cross-sectional cohort study of 36 patients (60 orbits). Preoperative and postoperative (6 months) orbital CT following extradural transorbital decompression was analyzed. Primary outcome measure was the percentage area of the cranial vault occupied by orbital and brain tissue in a predefined window before and after surgery. Secondary outcome measures were displacement of the anteriormost aspect of the temporal lobe, reduction in clinical proptosis, change in clinical activity score, and change in diplopia. Results: The mean percentage of the selected area of the cranial vault preoperatively was 0% orbital and 44% ± 15% brain tissue, compared with 70% ± 16% orbital and 28% ± 14% brain tissue postoperatively (p