Anatomical Features of Intratemporal Course of Facial Nerve and its Variations

Introduction Facial nerve has the longest and complex course in its bony canal. The anatomical variations make the nerve prone to injury during mastoid surgeries. Having a thorough anatomical knowledge and its variations is must for the surgeons to avoid injury to this vital structure and for the safe surgery. The objective of the study was to describe the anatomical variations of intratemporal portion of facial nerve. Materials and methods The study was conducted in the department of otorhinolaryngology in the temporal bone dissection laboratory of a tertiary health care centre. Fifty wet temporal bones were dissected by the same team of surgeons for the duration of one year to study the various anomalies of the intratemporal course of the facial nerve and its relations with the other important middle car structures. Results The mean length of the labyrinth, tympanic and mastoid segment of the facial nerve was 4.1 mm (+/- 0.6 mm), 9.34 mm (+/- 1.12 mm) and 12.8 mm (+/- 1.8 mm), respectively. The mean distance between the horizontal segment and posterior edge of the oval window was 3.1 mm (+/- 1.03 mm). Dehiscence in the tympanic segment was observed in three temporal bones (6%). Two (4%) specimens had bifurcation of the mastoid segment of the facial nerve. In all dissected temporal bones, the chorda tympani travelled in an ascending path. Conclusion The most common site for facial nerve anomaly is the tympanic portion. Anomalous conditions that can place the nerve at risk of being injured by the surgeons are highlighted here.