Effect of orbitotomy on surgical freedom in Endoscopic Transorbital Approach (ETOA) to the skull base: An anatomical study

Introduction

To investigate the angle of attacks and surgical freedom in different extents of orbitotomy for Endoscopic Transorbital Approach to the skull base.

Background

Endoscopic Transorbital Approach is gaining popularity among skull base surgeons over the last decade.The surgery can be performed with or without orbitotomy to increase surgical freedom for deeply seated intracranial lesion.

Study design

This is an anatomical and radiological study in which DICOM data of CT Brain is retrieved and analyzed for 4 types of orbitotomies (Group 1: supraorbital rim with lateral orbital rim resection; Group 2: limited supraorbital rim with lateral orbital rim resection; Group 3: lateral orbital rim resection; Group 4: No orbitotomy) on both sides of 19 patients. Angle of attacks and surgical freedom were calculated with reference to three dimensional coordinates of 4 target points (1. Foramen ovale; 2. Foramen rotundum; 3. End of lacerum segment of internal carotid artery; 4. Internal acoustic meatus) and compared.

Results

There is a statistically significant increase in surgical freedom, horizontal and vertical angle (p < 0.001) in Group 1 to 3 compared to Group 4 (No orbitotomy). With greater extent of orbitotomy, there is a larger increase in surgical freedom.

Conclusion

Removal of lateral orbital rim is useful to increase the angle of attack to skull base lesions whereas the area of orbitotomy is the main determinant of surgical freedom in ETOA. Lateral orbital rim removal should be considered when ETOA is used for deep seated skull base pathologies.