Morphometric analysis of internal acoustic meatus and its surgically relevant relations in human temporal bones

Internal acoustic meatus (IAM) is a chief landmark in various neuro-otological surgeries like removal of acoustic neuroma, temporal bone fractures and certain congenital anomalies. Understanding the anatomy of IAM is relevant during these surgeries to avoid injury to vital structures in its proximity like jugular bulb and saccus endolymphaticus. The aim of present study is to describe the morphometry of internal acoustic meatus with respect to the landmarks on postero-inferior surface of temporal bone and clivus. Twenty seven disarticulated temporal bones and thirty five dry skulls were used for the study. The shape of internal acoustic meatus was noted by direct inspection, whereas the dimensions such as vertical and horizontal diameter of internal acoustic meatus and its relation to important anatomical landmarks were measured in millimeters using digital vernier caliper. Internal acoustic meatus was either elliptical or round in shape. The average length and width of internal acoustic meatus was 7.51mm and 4.52 mm. The average distance from internal acoustic meatus to superior petrosal sulcus, jugular foramen, sigmoid sulcus, and clivus was 7.15mm, 7.77mm, 20.60mm, and 24.68mm respectively. The data obtained from the present study are anticipated to provide an insight for better surgical exposure of IAM and might prove to be beneficial minimizing the damage to vital structures in its proximity during any surgical procedures in this region.