The morphometric study of internal acoustic meatus in dry skulls of South Indian adults

Abstract

Background: The internal acoustic meatus (IAM) is a bony canal present between labyrinth and posterior cranial fossa. The normal morphometry of IAM is useful during evaluation of cases of skull trauma, congenital anomalies of IAM affecting the individual nerves, and in pre evaluation of surgeries of ear. The present study was done to determine the normal dimensions of IAM and to have a morphological database of the IAM for South Indian population. Materials & methods: The present study was conducted on 37 temporal bones of adult skulls. The impression of IAM was taken by injecting polyvinyl siloxane (PVS) impression material into the IAM and the dimensions were measured by using digital vernier callipers on right and left side separately. The height and width of IAM at porous, middle and fundus were measured and tabulated. Results: As there was no significant statistical difference between the parameters of right and left sides the data were pooled together. The mean height & width of IAM at porous end was 4.5mm & 6.42mm respectively. The mean height & width of IAC at its middle portion was 4.04mm & 4.91mm respectively. The mean height & width of IAM at the fundus was 3.8mm and 4.60mm respectively. The superior length & inferior length was 8.60 & 8.70mm respectively. Conclusion: This study provides a ready reference for dimensions of IAM of adult dry skull in South Indian population. The present study confirms that there is difference in the dimensions of IAM among different races and regions and thus emphasizes the need to have normal data for our population.

Keywords

• internal acoustic meatus
• temporal bone
• inner ear
• morphology