Using the zygomatic root as a reference point in temporal lobe surgery

Abstract

The zygomatic root (ZR) is an anatomic landmark routinely identified during cranial procedures. Traditionally, it has been used for identification of structures other than temporal lobe anatomy. The aim of this study was to define the structural relationship between the ZR and temporal lobe anatomy and provide a consistent landmark to guide surgical dissection. To our knowledge, there have been no studies demonstrating this relationship. Eighteen DICOM series were analyzed. 2 mm axial MRI slices were reconstructed with the x-axis centered along the zygoma. The posterior point of the ZR that marks the beginning of the groove between the zygoma and temporal bone was identified on all images. Several measures were taken to quantify the relationship of the zygomatic root to surgical landmarks used during temporal lobe surgery. The inferior temporal gyrus was always found just medial to the ZR. The mean distance between the ZR and temporal pole was 2.75 cm on the right and 2.78 cm on the left. The tip of the temporal horn was located on average 2.4 cm (left) and 2.31 cm (right) medial to the ZR. The tip of the temporal horn was found to be an average distance of 1 mm (left and right) posterior and 1.34 cm (left and right) superior to the ZR. All distances were measured orthogonally for each of the x, y, and z axes. The zygomatic root is an easily identifiable and consistent bony landmark that can serve as an adjuvant to neuronavigation for identification of temporal lobe surgical anatomy.