Reappraising the neurosurgical significance of the pterion location, morphology, and its relationship to optic canal and sphenoid ridge and neurosurgical implications

Analysis of the Variations in the Morphology, Topography of the Pterion, and Their Implications in Neurosurgery: An Osteometric Study

Objective  Pterion is an "H" shaped formation of sutures located in the temporal fossa of the skull. It is an important anatomical landmark and a craniometric point. The thinness of the skull and its inner relation with the middle meningeal artery make this anatomical landmark clinically significant. Variations in the pterion are imperative, especially for neurosurgeons in order to have the most suitable craniometric point to be minimally invasive. Materials and Methods  One hundred pterions were studied to report the variations in the type and location of the pterion. Murphy's classification was used to classify the pterion into four types on the basis of bone articulation-sphenoparietal, frontotemporal, stellate, and epipteric. Results  All four types of pterions were observed, sphenoparietal being the most common. No significant gender difference was observed in terms of type and laterality of various pterions. The mean distance between the center of pterion to the superolateral point of zygomaticotemporal (PZT) suture and the anterolateral point of the frontozygomatic (PFZ) suture were 3.91 ± 3.79 cm and 3.68 ± 3.79 mm, respectively. Correlation analysis showed a strong positive relation between PZT and PFZ sutures. Conclusion  Accurate data on the morphology and morphometry of bony anatomical points are crucial, while performing intracranial surgery using them as recognizable landmarks. The morphometric parameters may help in determining the soundness of the pterion as an identifiable landmark for performing interventions like burr hole and other neurosurgical procedures in this area.

Morphological types and localization patterns of pterion in the skulls of adults from southeastern China

PURPOSE

To study the morphological types and relative location of the pterion and its precise relationship with the middle meningeal artery (MMA) in the skulls of adults from southeastern China.

METHODS

Dry skulls (n = 250) of adults were obtained from a university specimen bank and analyzed. The morphological types of the pterions were observed. The distances from the center of the external pterion (Pec) to the relevant intracranial and extracranial marker points were measured using a digital vernier caliper. The anterior, middle, and posterior end points of the external pterion were drilled perpendicular to the bone surface. The precise relationships of the external pterion with the internal pterion and the groove of the frontal branch of the MMA were observed and measured after sawing the skull.

RESULTS

The morphological types of the pterion in the skulls of adults from southeastern China were sphenoparietal suture (SP) (85%), epipteric (12.4%), frontotemporal suture (1.4%), and stellate (1.2%) types. The mean widths of the external and internal pterions were R, 10.68 ± 4.22 mm; L, 11.13 ± 4.40 mm and R, 14.66 ± 4.04 mm; L, 14.14 ± 4.29 mm, respectively, and the width of the internal pterion was slightly longer than that of the external (P < 0.05). No significant difference in pterion width was found between the genders or sides of the skull (both P > 0.05). The distances from the Pec to the posterolateral aspect of the frontozygomatic suture, zygomatic process of the frontal bone, midpoint of the zygomatic arch, and external acoustic meatus were 29.95 ± 3.75 mm, 34.88 ± 4.08 mm, 40.86 ± 3.59 mm, and 53.79 ± 3.82 mm, respectively. These distances were slightly longer on the right side of the skull than on the left side (P < 0.01) and longer in men than in women (P < 0.01). The distances from the Pec to the frontal crest, optic canal, and anterior clinoid process were 62.79 ± 1.15 mm, 45.39 ± 2.48 mm, and 45.47 ± 2.05 mm, respectively. The external and internal pterions were not on the same level, and all the internal pterions were located below the external ones. In the vast majority of the skulls, the groove of the frontal branch of the MMA passed through the posterior end of the external pterion (Pep) or the area between the Pec and Pep.

CONCLUSION

The morphology of the pterion in the skulls of adults from southeastern China is predominantly of the SP type, mostly symmetrically distributed. The distance from the pterion to the extracranially relevant marker points differs among the ethnic groups, between the genders, and between the sides of the skull. All the internal pterions are located below the external ones. Most of the frontal branch of the MMA is located below the mid-posterior segment of the lateral pterion. The characterization of the morphology, the relative position of the pterion and the precise relationship of this structure with the MMA in the skulls of adults from southeastern China may provide an anatomical basis for teaching and clinical practices.

Positions and Types of Pterion in Adult Human Skulls: A Preliminary Study

BACKGROUND

A trauma to the skull in the area of the pterion usually causes rupture of the middle meningeal artery leading to life- threatening epidural hematoma. The objective of the study is to assess the prevalence of different types of pterion and to determine its location using valuable bony landmarks.

METHODS

On 90 dry adult human skulls of unknown sex, age and nationality the distance of different landmarks from pterion was measured using stainless steel sliding Vernier caliper. The data were analyzed using SPSS version-20 and an independent t-test analysis was implemented. A value of P< 0.05 was considered as statistically significant.

RESULTS

A higher occurrence of sphenoparietal type of pterion with the absence of frontotemporal type was noted. About 23% and 77% of the suture types are found to be unilateral and bilateral, respectively. There was a statistically significant difference between right and left sides of the skull in distances from the center of pterion to frontozygomatic suture, root of zygomatic arch, inion and in central thickness pterion.

CONCLUSION

This study showed that the most prevalent type of pterion is sphenoparietal, and revealed asymmetry in the distances from center of pterion to frontozygomatic suture, root of zygomatic arch and inion, and its central thickness. Such findings could offer worthy information about the type and location of pterion, which could be relevant to anatomists, neurosurgeons, forensic medicine specialist and anthropologists.