Study of intratemporal course of facial nerve and its variations — 25 temporal bones dissection

Abstract

Facial nerve is the longest nerve in a bony canal. Three dimensional anatomical knowledge provides the foundation for safe and skillful dissection of the very complex temporal bone and tortuous facial nerve. A small surgical area and a fair incidence of anatomical variations makes the facial nerve prone to injury. Inspite of the problems presented, the nerve serves as an excellent landmark and guide to the competent otological surgeon who studies it deligently, the neophyte on the other hand lives in constant fear of finding the nerve inadvertently. The present study was undertaken to explore the microanatomy of tympano-mastoid segment of facial nerve. The current study was conducted at Dept of E.N.T, temporal bone lab, J.N.M.C Sawangi, Wardha. 25 temporal bones were dissected to study the various parameters of the tympano-mastoid segments of the facial nerve, its relations with the important middle ear structures and their anomalies. Mean length of tympanic segment was 9.28mm and that of the mastoid segment was 13.7mm. Mean depth of second genu from the cortex was 19.72mm. Amongst the variations noted commonest were the variations in the tympanic segment of about 12 %. An overhang in the region of oval window and a hump at the second genu was noted in one specimen each. The variations in the tympanomastoid segment occur with sufficient frequency showing not much racial and geographical variance.