Study of anatomical variation of asterion in human dry skulls and its surgical importance

Saravana Kumar S*, Lalitha R, Gnanavel A

Meenakshi Medical college Hospitals & Research Institute, Chennai, Tamil Nadu, India

ABSTRACT

Asterion is the meeting point of temporal, occipital, and parietal bones on the posterolateral surface of the skull. This point is surgically important in various posterior cranial fossa surgeries since it is a smaller delicate area where many vital structures are present. The Neurosurgeons have been doubtful about its accuracy due to population-based differences in its morphology and its location with relationship to sigmoid and transverse sinuses. In this study 100 (54 male & 46 female) adult skulls were measured to accurately the type of asterion, its distance from important bony landmarks, and also the nearby venous sinuses were measured. Our study revealed that type II (absence of sutural bones) is the commonest type when compared to type I (presence of sutural bones) asterion. The asterion was 4.82 ± 0.58 cm from the apex of the mastoid process on the right side and 4.70 ± 0.70 cm on the left. It was higher in males than in females, p-value being statistically significant (P = 0.00 & P = 0.02 for right & left sides respectively). The distance of asterion from supramastoid crest is 4.22 ± 0.73 cm on the right and 4.23+/-0.58 cm on the left. The distance in males is higher than in females. The position of the asterion in relation to transverse sinus was at the level of the transverse sinus in 74.67% of cases, and inferior to the asterion in 22.41%, and superior to the asterion in 2.92%. The measure taken reveals that the asterion is located either at the level or below the level of the transverse sinus in the majority of the cases. This information is useful to neurosurgeons to minimize the risk during posterior cranial fossa surgeries. This study is useful for anthropologists, forensic science experts for the determination of the sex of the skull along with other parameters.

Keywords:

Asterion, Transverse sinus, Mastoid process, Approach to posterior cranial fossa.