MORPHOMETRIC STUDY OF PTERION IN DRY ADULT HUMAN SKULLS

Address for Correspondence: Dr. Mrunal K Muley, Assistant Professor, Department of Anatomy, G.M.C. Aurangabad, Maharashta, India. E-Mail: mrunal.137@gmail.com Introduction: The pterion corresponds to the site of anterolateral fontanelle of the neonatal skull which closes at third month after birth. In the pterional fractures the anterior and middle meningeal arterial ramus ruptures commonly which results in extradural hemorrhage. Pterional approach is most suitable and minimally invasive approach in neurosurgery. Materials and Methods: The present study was carried out on the pterion of 36 dry adult skulls of known sex from department of anatomy GMC Aurangabad Maharashtra. Results: The mean and standard deviation of the distance between the centre of pterion to various anatomical landmarks. The distance between Pterionfrontozygomatic (P-FZ) suture 29.81±4.42mm on right side, 29.81±4.07mm on left side; Pterion-Zygomatic arch (P-Z) 37.16±3.77mm on right side, 37.56±3.71mm on left side, Pterion-asterion (P-A) 89.73±6.16mm on right side, 89.46±6.35mm on left side; Pterion-external acoustic meatus (PEAM) 53.40±7.28mm on right side, 53.57±6.73mm on left side, PterionMastoid process (P-M) 80.35±3.44mm on right side, 80.96±3.79mm on left side and PterionPterion (P-P) 194.54±16.39mm were measured. Conclusion: The data constructed in the present study will be of immense importance while performing pterional approach surgeries in Indian population.


INTRODUCTION
closes at third month after birth [2].According Moore & Dalley [3] reported that the pterion is two fingers' breadth superior to the zygomatic arch and a thumb's breadth posterior to the frontal process of the zygomatic bone.
Pterion is an important guide for age and sex determination as well as archaeological and Forensic estimation.It is also an important site to assess anterior branch of middle meningeal Pterion is defined as an H-shaped small circular area formed by the junction of four bones: frontal, parietal, temporal and sphenoid on norma lateralis of the skull, being approximately 4cm above the zygomatic arch and 3.5 cm behind frontozygomatic suture [1].
The pterion corresponds to the site of anterolateral fontanelle of the neonatal skull which artery, Broca's area, sphenoid ridge and optic canal [4].
In the pterional fracures the anterior and middle meningeal arterial ramus ruptures commonly which results in extradural hemorrhage.Pterional approach is most suitable and minimally invasive approach in neurosurgery.It is used to access to structures of anterior and middle cranial fossae.Pterional approaches have paved the way for the management of wide variety of neurological disorders in the anterior, middle and upper part of posterior cranial fossa with minimal tissue injury, without compromising surgical results [5].So proper knowledge of pterion, its topography and morphology is mandatory for the pterional approach used in the neurosurgery.
This morphometric analysis will be of immense importance while performing pterional approaches in neurosurgical procedures in Indian population.

Pterion-Mastoid process (P-M):
The distance between pterion to the tip of the mastoid process.

MATERIALS AND METHODS
The present study was carried out on the pterion of 36 dry adult skulls of known sex.The skulls with pathological lesions and damage were excluded.Samples were collected from department of anatomy GMC Aurangabad Maharashtra.
Material used for taking measurement Digital Vernier Caliper, cotton thread, scale.For the measurement of the distance of pterion from different bony landmarks, the centre of pterion was first established.Readings were taken twice and mean of two readings was taken to avoid error.

Following measurements were studied
Pterion-frontozygomatic suture (P-FZ): Distance from centre of to the posterolateral aspect of the frontozygomatic suture.

Pterion-Zygomatic arch (P-Z):
The distance from the centre of pterion to the superior edge of the midpoint of zygomatic arch.

Pterion -asterion (P-A):
The distance between centre of pterion and at asterion.

Pterion-external acoustic meatus (P-EAM):
The distance between centre of pterion to the anteriosuperior margin of external acoustic meatus.
The mean and standard deviation of the distance between the centre of pterion to various anatomical landmarks are tabulated as follows: No significant variation on right and left side was observed in various parameters measured from the centre of pterion.
Mishra et al [1] found that the mean distance P-EAM was 5.12cm on right side, 5.19cm on left side; P-M was 8.13cm on right side and 8.02cm on left side.K Epharaim Vikram Rao et al [2] observed that the distances of centre of pterion from midpoint of zygomatic arch (P-FZ) was 37.74±3.66 on right side, 37.07±4.19 on left side; P-F was 30.48±4.06 on right side, 30.39±4.70 on left side; P-EAM was 51.81±4.08onright side, 51.54±3.89 on left side and P-M was 80.40±6.43 on right side and 79.68±6.08 on left side.

DISCUSSION
Pterional approach was considered as the minimally invasive neurosurgical approach ideal for anterior and middle cranial fossa lesion [6].The location of pterion and its relation to the surrounding bony landmarks is important.Such detailed information can only precisely be obtained from an examination of dry Skulls.

CONCLUSION
The present study concludes that the location of pterion in relation to different bony landmarks are important in neurosurgeries or mini-craniotomy while approaching anterior or middle cranial fossa.Such detailed information can readily be obtained from morphometric study of dry skulls.However, as imaging techniques continue to develop, it may be possible to determine more precise relationships between bony landmarks and the underlying soft tissues.
The data constructed in the present study will be of immense importance while performing pterional approach surgeries in Indian population.

Table 1 :
Distance of pterion from various bony landmarks.

Table 2 :
Comparison between distances of centre of pterion from different bony landmarks in previous studies and present study.

The distance between Pterion-Zygomatic arch (P-FZ) (cm) The distance between Pterion-Zygomatic arch
(P-Z) (cm) Results of current study are in line with Mishra et al 1 and K Epharaim Vikram Rao 2 Mwachaka et al [8] Apinhasmit et al [11] Kumar S. et al [13] Whereas mean values of present study are slightly less than those of Oguz et al [7], Ukohla et al [12] and Eboh and Obaroefe [14].