The Laryngoscope Lippincott Williams & Wilkins, Inc., Philadelphia © 2001 The American Laryngological, Rhinological and Otological Society, Inc. Use of Reconstructed Sagittal Computed Tomography Images to Plan Middle Cranial Fossa Surgery Krista L. Olson, MD; Spiros Manolidis, MD; L. Anne Hayman, MD; Ling-Ling Chan, MD; Katherine H. Taber, MD Objective: To facilitate planning in temporal bone surgery for the middle cranial fossa approach by using sagittal reconstructed temporal bone computed tomog- raphy images. Study Design: Comparison of anatomic measurements on random high-resolution, reformatted computed tomography scans of the temporal bone. Methods: High-resolution computed tomography of 10 normal temporal bones in the axial and coronal planes was obtained, and two-dimensional sagittal reconstruc- tions were performed using a commercial software pro- gram. Eight anatomical relationships between neural and/or vascular structures were measured. Representa- tive images were inverted to recreate the plane of the middle cranial fossa approach. Results: Anatomical re- lationships among the vestibule, superior semicircular canal, internal auditory canal, internal carotid artery, and middle cranial fossa exhibited a high SD in the 10 subjects. The sample size and the large range for the eight anatomical relationships precluded the detection of a significant difference between right and left tempo- ral bones or sex and age of the patient. Conclusion: The present report presents a novel, practical measurement protocol for rapidly evaluating important individual anatomical differences in patients before middle cra- nial fossa surgery. Inverted sagittal reconstructions fa- cilitate presurgical planning for the middle cranial fossa approach by 1) assessing critical anatomical rela- tionships before surgery and 2) providing customized measurements between vital landmarks and the first in vivo measurements. This decreases the likelihood of surgical mishaps and improves teaching by providing the first in vivo measurements of practical anatomical relationships in the sagittal plane. Key Words: Temporal bone, high-resolution computed tomography, middle cranial fossa approach, computed tomography, image display and recording. Laryngoscope, 111:2095–2099, 2001 INTRODUCTION In the middle cranial fossa (MCF) approach for otologi- cal surgery, the surgeon is positioned so that the line of vision (and, consequently, bone removal) is not comparable to axial and coronal computed tomography (CT) planes of section. In this setting, it is useful for the surgeon to visualize the temporal bone anatomy in the inverted sagittal plane. In the traditional MCF approach, bone is removed in a rostrocaudal direction to expose the underlying land- marks and allow access to the distal and proximal internal auditory canal (IAC). In the extended MCF approach, bone is removed toward the petrous apex, widely exposing the underlying petrous carotid and allowing access to the petroclival region. In these approaches, the anatomical relationships between the geniculate ganglion, labyrin- thine segment of the facial nerve, IAC, superior semicir- cular canal (superior SCC), and the underlying cochlea and vestibule are of critical importance. In the extended MCF approach, additional structures gain importance, such as the canal of the petrous carotid, the petroclival region, and the foramina of the skull base that transmit cranial nerves. Although these anatomical landmarks can be visualized in the axial and coronal planes of conven- tional CT imaging, they are ideally seen through inverted sagittal high-resolution computed tomography (HRCT) re- constructed images that reproduce the surgical dissection plane. The authors undertook the present study to deter- mine whether a simple and practical imaging protocol that uses commonly available software and a patient’s previ- ously acquired axial clinical scans could illustrate these surgical planes and accurately measure distances between surgical anatomical landmarks. MATERIALS AND METHODS Ten temporal bone HRCT scans from 10 patients (8 adult [age range, 22– 62 y; median age, 41 y] and 2 pediatric [age range, Presented at the Western Section Meeting of the Triological Society, Palm Desert, CA, May 14, 2001. From The Bobby R. Alford Department of Otorhinolaryngology and Communicative Sciences (K.L.O., S.M.), the Department of Radiology (L.A.H., L-L.C., K.H.T.), and the Herbert J. Frensley Center for Imaging Research (L.A.H., K.H.T.), Baylor College of Medicine, Houston, Texas, U.S.A. Editor’s Note: This Manuscript was accepted for publication July 17, 2001. Send Correspondence to Spiros Manolidis, MD, Baylor College of Medicine, The Bobby R. Alford Department of Otolaryngology and Com- municative Sciences, 6550 Fannin, Suite 1727, Houston, TX 77030, U.S.A. E-mail spirosm@bcm.tmc.edu Laryngoscope 111: December 2001 Olson et al.: Planning Middle Cranial Fossa Surgery 2095