The arcuate eminence (AE) is an anatomically consistent bony protrusion located on the upper surface of the petrous bone that has been previously studied as a reference for lateral skull base approaches. There is a paucity of information in the neurosurgical literature seeking to improve the safety of the extended middle cranial fossa (MCF) approach using detailed morphometric analysis of the AE.
To evaluate the use of the AE as an anatomical landmark to help with early identification of the internal acoustic canal (IAC) in MCF approaches by means of a cadaveric study, using a new morphometric reference termed the \"M-point.\"
A total of 40 dry temporal bones and 2 formalin-preserved, latex-injected cadaveric heads were used. The M-point was established as a new anatomic reference by identifying the intersection of a line perpendicular to the alignment of the petrous ridge (PR), originating from the midpoint of the AE, with the PR itself. Subsequent anatomical measurements were performed to measure the distance between M-point and IAC. Additional distances, including PR length and the anteroposterior and lateral AE surfaces, were also measured.
The mean distance between the M-point and the center of the IAC was 14.9 mm (SD ± 2.09), offering a safe drilling area during an MCF approach.
This study provides novel information on identification of a new anatomic reference point known as the M-point that that can be used to improve early surgical identification of the IAC.

BACKGROUND: The anterior petrosectomy approach is among the most popular for exposure of the petroclival region. However, the complexity of the anatomy, drilling time required, and risk of injury to neurovascular structures have made this procedure especially challenging. We have proposed a novel combined extradural-intradural technique for en bloc anterior petrosectomy-or one-piece Kawase-and have charted the landmarks that define its surgical boundaries.
METHODS: The approach was performed on 14 embalmed specimens. The one-piece Kawase approach consists of 3 extradural drilling steps, followed by incision of the dura and skeletonization of the superior petrosal sinus. The procedure culminates with 2 intradural drilling steps. The bone piece was then removed en bloc, and the maximum anteroposterior, superoinferior, and mediolateral lengths were recorded. The linear distances between the main neurovascular landmarks were also measured using a stereotactic navigation system.
RESULTS: The mean measurements were 17.6 ± 2.6 mm for the anteroposterior distance, 10.5 ± 2.3 mm for the superoinferior distance, and 9.5 ± 2.6 mm for the mediolateral distance. The medial linear distance from the mandibular nerve/greater superficial petrosal nerve to the internal carotid artery was 6.8 ± 1.3 mm, to the facial hiatus was 11.6 ± 2.2 mm, and to the lateral internal acoustic canal was 17.9 ± 1.8 mm. The average distance from the porus trigeminus to the medial internal acoustic canal was 19.4 mm.
CONCLUSIONS: The advantages of this technique include the wide exposure of the petroclival region, extensive visualization of critical structures via extradural and intradural corridors, and minimization of bone drilling, which could reduce heat damage. Clinical application of the illustrated technique is required to test its reliability in different pathological subsets.

Objective Multiple landmarks and anatomic relationships exist to identify internal acoustic canal (IAC) in middle fossa approach for removing intracanalicular schwannomas. We attempted to identify a reproducible, practical method to quickly identify the IAC that would be applicable when an expanded middle fossa approach is required. Design Middle fossa approach was performed on 10 cadavers (21 dissections). In the first head, temporal and suboccipital craniotomies were performed to identify landmarks and formulate a hypothesis. Porous acusticus (PA) was identified and IAC was circumferentially skeletonized into middle fossa. Orientation of IAC in the middle fossa was evaluated in relation to foramen spinosum (FS), foramen ovale (FO), petrous ridge, and petrous apex. Consistency of this relationship was tested in the remaining heads. Results The opening of PA (point A) was consistently found at a mean of 2.38 cm posterolateral to the petrous apex along the petrous ridge (range 2.1 to 2.8). A line was drawn from the FO to FS and extrapolated posteriorly. The IAC (point B) was found a mean distance of 2.39 cm from FS along the FS-FO line (range 2.1 to 2.8). The course of IAC was consistently found by connecting point A to point B. Conclusion A novel, practical, and reproducible method is described to identify the IAC via the expanded middle fossa approach.

This article presents the results of a validation study of a previously published method of sex determination from the temporal bone. The purpose of this study was to evaluate the lateral angle method for the internal acoustic canal for accurately determining the sex of human skeletal remains using measurements taken from computed tomography (CT) scans. Previous reports have observed that the lateral angle size in females is significantly larger than in males. The method was applied to an independent series of 77 postmortem CT scans (42 males, 35 females) to validate its accuracy and reliability. The mean lateral angle of the internal acoustic canal was found to be larger in females (46.5°) than in males (43.4°). However, the difference was not statistically significant and the sex differences reported in previous studies were not substantiated. In light of the observed results, the lateral angle method appears to be of minimal practical use in forensic anthropology and archeology.