Occupation Size of Internal Acoustic Opening in Facies Posterior of Petrous Part of Temporal Bone

[LANGUAGE= "English"] Purpose: Internal acoustic meatus is about one cm length and opens near the center of posterior surface of the petrous part of temporal bone. The aim of the study was to analyze the occupation of porus acousticus internus in facies posterior of petrous part of temporal bone.Material and Methods: In this study, 100 temporal bones of 50 dry skulls (unknown sex) were examined. The areas of whole surface of the facies posterior of petrous part and porus acousticus internus were calculated with the help of the Cavalieri principle. The ratio of the porus acousticus internus to facies posterior was calculated. The posterior wall length of internal acoustic meatus vertical and sagittal diameter of the porus were also measured.Results: The ratio of area of the porus acousticus internus to facies posterior partis petrosa was 4.82% on the right and 4.54% on the left. The length of the posterior wall was 15mm on the right and 14 mm on the left. Vertical diameter was 4.51mm on the right and 4.55mm on the left and sagittal diameter was 6.85mm on the right and 6.61mm on the left.Conclusion: The measurement of the distances could be useful in guiding the degree of bony removal for safety surgery.