The Morphological and Morphometric Examination of the Asterion in Terms of Surgical Approaches to the Posterior Cranial Fossa

Abstract

Objective: The asterion is an important cranial anatomical landmark used in surgical approaches to the posterior cranial fossa, which is one of the most complex and surgically challenging regions of human anatomy due to the density of neurovascular structures. This study aims to examine the morphological and morphometric variations of the asterion to determine its preoperative localisation and help neurosurgeons reduce possible complications by providing an understanding of the detailed anatomy of the asterion in surgical approaches applied in posterior cranial fossa pathologies.

Methods: In our study, adult human dry skull specimens (44 intact, 104 hemi skulls) with unknown demographic data were analysed. The asterions were first examined morphologically and categorised into two classifications. These classifications were based on the presence of wormian bone and the distance from the Frankfurt horizontal plane (FHP). Morphometric measurements were based on anatomical landmarks in the human skull. The landmarks used in the measurements were the lambda (L), FHP, the root of the zygomatic arch (RZA), the tip of the mastoid process (TMP), Henle’s spine (HS), external occipital protuberance (EOP), basion (B), opisthion (O) and porion (P).

Results: The morphological classification of the asterions was examined. Type 1 and Type 2 were determined as 13.02% and 86.98%, respectively, according to the presence of the wormian bone. In the classification, according to the distance to the FHP, Type 1 was 9.90%, Type 2 was 58.85% and Type 3 was 31.25%. In morphometric measurements, the mean distance of the asterion to L was 85.16 ± 5.64 mm and 84.41 ± 5.43 mm on the right and left sides, respectively. The mean distance of the asterion to the FHP was 13.17 ± 6.81 mm and 14.01 ± 6.96 mm on the right and left sides, respectively. The mean distance of the asterion to the RZA was 56.18 ± 3.58 mm and 56.64 ± 3.69 mm on the right and left sides, respectively. The mean distance of the asterion to the TMP was 49.42 ± 4.16 mm and 48.91 ± 4.03 mm on the right and left sides, respectively. The mean distance of the asterion to HS was 46.15 ± 3.74 mm and 46.69 ± 3.79 mm on the right and left sides, respectively. The mean distance of the asterion to the EOP was 63.19 ± 4.13 mm and 62.71 ± 4.07 mm on the right and left sides, respectively. The mean distance of the asterion to B was 73.50 ± 3.73 mm and 72.96 ± 3.51 mm on the right and left sides, respectively. The mean distance of the asterion to O was 62.46 ± 2.88 mm and 62.23 ± 2.85 mm on the right and left sides, respectively. Finally, the mean distance of the asterion to P was 49.51 ± 3.87 mm and 50.32 ± 3.94 mm on the right and left sides, respectively.

Conclusion: The results obtained in our study suggest that the accurate preoperative positioning of the asterion may contribute to reducing complications that may develop in neurosurgeons’ surgical approaches to the posterior cranial fossa.