Epipteric Bones in the Pterion May Be a Surgical Pitfall

Abstract

Background: The pterion, the most commonly used neurosurgical landmark, is defined as the junction of frontal, parietal, and greater wing of the sphenoid and the squamous part of temporal bones. Our aim was to identify the variations of the pterion which may be a potential surgical pitfall.
Methods: Both sides of 300 adult skulls were examined but 110 sides were eliminated since their pterion could not be identified owing to a damage. The shortest distance between the lateral orbital rim and the most anterior junction of the four bones forming the pterion was measured on all sides.
Results: Out of 490 sides the pterion was found to contain epipteric bones in 44 (9 %), and in these skulls the most anterior junction of the bones may be as close as 16 mm to the lateral orbital rim.
Conclusion: In skulls with an epipteric bone variation, particularly the anterius and proprium types; the pterion can mistakenly be assessed to be at the most anterior junction of bones and a burr hole placed over there may cause inadvertent penetration into the orbit.

Anatomy - cranium - variation - neurosurgery

References

• 1 Day J D, Tschabitscher M. Anatomic position of the asterion.  Neurosurgery. 1998;  42 198-199
• 2 Wen H T, De Oliviera E, Tedeschi H, Andrade F CJ, Rhoton A LJ. The pterional approach: Surgical anatomy, operative technique, and rationale.  Operative techniques in Neurosurgery. 2001;  4 60-72
• 3 Lang J. Skull base and related structures: atlas of clinical anatomy. Stuttgart: Schattauer 1995: 118
• 4 Yaşargil M G. Microsurgical anatomy of the basal cisterns and vessels of the brain. Microneurosurgery. Vol. 1 Stuttgart: Georg Thieme Verlag 1984: 220
• 5 Lang J. The fronto-temporal region and its clinically important distance from the optic nerve. 1. The fronto temporal region.  Neurochirurgia (Stuttg). 1983;  26 161-163
• 6 Yaşargil M G, Antic J, Laciga R, Jain K K, Hodosh R M, Smith R D. Microsurgical pterional approach to aneurysms of the basilar bifurcation.  Surg Neurol. 1976;  6 83-91
• 7 Broca P. Instructions craniologies et craniometriques.  Mem Soc d'Anthrop. 1875;  2 159-336 (cited in ref. 9)
• 8 Asala S A, Mbajiorgu F E. Epigenetic variation in the Nigerian skull: sutural pattern at the pterion.  East Afr Med J. 1996;  73 484-486
• 9 Agarwal A K, Singh P, Gupta S C, Gupta C D. Pterion formation and its variations in the skulls of Northern India.  Anthropol Anz. 1980;  38 265-269
• 10 Matsumura G, Kida K, Ichikawa R, Kodama G. Pterion and epipteric bones in Japanese adults and fetuses, with special reference to their formation and variations.  Kaibogaku Zasshi. 1991;  66 462-471
• 11 Saxena S K, Jain S P, Chowdhary D S. A comparative study of pterion formation and its variations in the skulls of Nigerians and Indians.  Anthropol Anz. 1988;  46 75-82
• 12 Broek A JPvd. On pteric sutures and pteric bones in the human skull.  Kon Akad Wetenesch Amsterdam, Proc Sect Sci. 1914;  6 634-639 (cited in ref. 9)
• 13 Lange B. Über Rassenunterschiede an der Regio pterica beim Menschen.  Anat Anz. 1924;  58 353-374 (cited in ref. 3)