The Apex of the Mastoid Process as a Fixed Point in Determining the Location of the Entry of the Facial Nerve to the External Base of the Skull

Abstract

Objective: This study examined how the stylomastoid foramen (SMF) relates anatomically to the mastoid process apex, analyzing variations by cranial type (brachy-, meso-, dolichocranic) and age groups, aiming to guide facial nerve blocks and surgical access. Materials and Methods: Researchers measured the distance from the SMF left to the mastoid apex and the α‑angle between SMF axis and the Frankfurt horizontal plane in 159 dry human skulls, categorized by the cephalic index and six age brackets. Results: Significant differences were found across cranial types and age groups. Dolichocranic skulls exhibited the longest SMF–apex distance, while brachycranic skulls had the deepest SMF position and largest α‑angle. The middle-age groups and dolichocranic types displayed lower α‑angles, indicating morphological shifts with age and skull shape. Conclusion: The mastoid apex is a reliable landmark for locating the SMF, but its spatial relationship varies with cranial morphology and age. These insights may improve the accuracy of facial nerve blockade and reduce risks during parotid or mastoid surgery.

Keywords

• Stylomastoid foramen
• Mastoid process
• Brachycranes dolichocranic
• Mesocranes

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