A study on the pterion position variation and its neurosurgical implications

Introduction: The pterion is a neurosurgical landmark on the lateral aspect of the skull providing access to vital structures such as sylvian fissure, circle of Willis, optic nerve, para-sellar regions, middle meningeal vessels and cavernous sinus. The bilateral and gender variation in the pterion position was analyzed. Methods: The linear distance of the centre of the pterion from midpoint of zygoma and frontozygomatic suture was measured bilaterally in both sexes in adult dry skulls of Indian ethnic group. This was analyzed statistically using histogram, Student's t-test, binary logistic regression and receiver operating characteristic curve. Results: The mean distance of the centre of the pterion from midpoint of zygoma was 36.85 +/- 4.12 mm and 34.35 +/- 3.18 mm and its distance from frontozygomatic suture was 31.90 +/- 4.14 mm and 29.72 +/- 3.75 mm in males and females respectively. The position of the pterion exhibited statistically significant sexual dimorphism, with distance of the pterion from midpoint of zygoma having a p value <0.001 and a sex predictability of 67% and its distance from frontozygomatic suture a p value of 0.001 and sex predictability of 65.3%. Discussion: The pterion position is higher in males than females and literature review also reveals significant ethnic variation. This knowledge of gender and ethnic variation is essential for a neurosurgeon while drilling a burr hole at the pterion to prevent orbital penetration due to an anterior drilling and an ineffective access for instrumentation due to a posterior drilling. (C) 2016 Anatomical Society of India. Published by Elsevier, a division of Reed Elsevier India, Pvt. Ltd. All rights reserved.