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IP Indian Journal of Anatomy and Surgery of Head, Neck and Brain


Surface Projection of Internal Acoustic Meatus


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Author Details: Swayam Jothi. S

Volume : 2

Issue : 1

Online ISSN : 2581-5229

Print ISSN : 2581-5210

Article First Page : 1

Article End Page : 15


Abstract

Introduction: The cerebellopontine angle tumours account for 8% of all intracranial tumours in infants. Today, the availability of non-invasive imaging procedure such as CT scan and MRI, make it easy to diagnose them and some successful operations have been done by enlarged middle cranial fossa approach (Haider, 1992). When translabyrinthine and middle cranial fossa approaches are contraindicated, the posterior cranial fossa approach could be tried for cerebellopontine angle tumours.
Aim: This study aims to collect adequate gross information which may be of help in various surgical interventions of the facial nerve; for example cerebellopontine angle tumours.
Materials & Methods: 39 fetal craniums were used for measurements to locate the internal acoustic meatus from surface. Two intact fetal heads were used to confirm this method of reaching the Internal Acoustic meatus (IAM) from the entry point.
Cranial index was calculated for all the skulls: For surgical procedures to reach the IAM from surface and for biopsy with a needle, the following measurements were made.

1.       Distance between the entry point and surface point.

2.     The angle between the entry point, internal acoustic meatus, and the surface point.

3.       Depth of IAM from EP.

Observation: Percentage ratio of the entry point to cranial index, IAM to cranial index & depth of IAM to cranial index respectively, the mean value were found to be 3.11, 45.3 & 4.13 respectively. The constants derived were utilized to locate the entry point of the needle, angle of passage and the depth to which it should be passed. The validity of this method was verified in the 39 exposed craniums. Two intact fetal heads were used to confirm this method of reaching the IAM from the entry point.

Keywords: Cerebellopontine angle tumours, Facial nerve, Internal acoustic meatus (IAM)