A Morphometric Analysis of the Middle Cranial Fossa in Mexican Adults for Dolenc and Kawase Approaches With Computed Tomography, 3D Reconstruction and Dry Skulls

TL;DR

This study measures the middle cranial fossa in Mexican adults using CT scans and dry skulls to improve surgical approaches like Dolenc and Kawase.

Contribution

The study provides the first population-specific morphometric norms for Mexican adults to guide middle fossa surgical approaches.

Findings

CT scans reliably measure FO-FS distances for extradural orientation in middle fossa approaches.

CT underestimates FO-AE and FS-AE distances compared to dry skulls, affecting Kawase approach planning.

The innominate pillar is a consistent landmark for locating CN V3 between FO and FS.

Abstract

Background: Accurate middle cranial fossa (MCF) morphometry is crucial for the safe application of middle fossa approaches such as the Dolenc and Kawase approaches, which expand exposure to the cavernous sinus and petroclival region. These parameters vary widely among individuals and populations, making population-specific data important. We therefore collected MCF measurements in Mexican adults using both CT scans and dry skulls to establish normative values and assess the accuracy of CT scans.

Methods: Two cohorts (97/107 subjects each) were analyzed: head CT scans (in vivo) and dry skulls (ex vivo) of adult Mexicans. Key distances (Foramen ovale (FO) - Foramen spinosum (FS), FO - arcuate eminence (AE), FS - AE) and innominate pillar thickness were measured bilaterally (each in duplicate). CT versus skull differences were tested (α = 0.05) using side-to-side symmetry analysis, and the 5th/95th percentiles were used as anatomical limits.

Results: CT and osteology showed close concordance for FO-FS, supporting CT-based extradural orientation for the middle fossa approach. In contrast, FO-AE and FS-AE were larger on dry skulls by a few millimeters, indicating that routine CT slightly underestimates the drillable petroclival window relevant to Kawase. The innominate pillar was consistently present and appeared slightly thicker on CT (partial-volume effect), remaining a practical landmark to localize CN V3 (mandibular division of the trigeminal nerve) between FO and FS. Left-right asymmetry was not evident on CT; osteology showed only small AE-related leftward tendencies. Percentile guardrails (P5, P50, P95) provide pragmatic bounds for preoperative planning.

Conclusions: This study provides the first MCF morphometric norms for Mexican adults to support safer, individualized Dolenc, Kawase, and middle fossa approach planning. CT-based measurements are largely reliable for surgical planning, although they slightly underestimate the Kawase approach reference points.

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