Our Experience of Anatomical Variations of Facial Nerve in Cadaveric Temporal Bone Dissection

Cadaveric dissections helps aspiring ear surgeon to learn anatomy of temporal bone so as to avoid injury to the many vital structures. Objectives are to study the course of facial nerve and its variation in 50 cases of temporal bone dissection. To study the various parameter of the tympanomastoid segments of facial nerve, its relation with the important middle ear structures and their variations. To study the incidence of anatomical variations such as dehiscence of bony canal of facial nerve, bony overhang in the oval window region. The Current study was conducted at Dept. of ENT Temporal bone lab. 50 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. The present study was carried out from Jan 2016 to Jan 2019. Out of 50 bones dissected, 44 (88%) bones were well pneumatised and 6(12%) bones were sclerotic. Length of the tympanic segment varied from 7.8 to 11.88 mm with a mean of 9.47 mm (± 1.06 mm). In 17 bones (34%) length of the mastoid segment was 13.1-14 mm, in 12 bones (24%) the length was 14.1-15 mm, while in 10 bones (20%) it was 12-13 mm. In 6 bones (12%) it was 15.1-16 mm and < 12 mm in 5 other bones (10%). The distance of second genu from outer cortex varied from 17.87-23.67 mm with a mean of 19.64 mm (± 1.42 mm).Distance of chorda tympani from stylomastoid foramina varied from 3.4-7.8 mm with a mean of 5.69 mm (± 1.51 mm). The study has provided knowledge of anatomy of temporal bone and its pneumatization pattern, the anatomy of the facial nerve, its variations and their incidence, relation of various middle ear landmarks with the facial nerve and proficiency in dissection.