The Intratemporal Course Variations of Facial Nerve in Wet Cadaveric Temporal Bones.

Abstract

The facial nerve is highly tortuous and has the longest course through a bony canal among all body nerves. Its course shares similarities and variations with other middle ear structures, making it susceptible to iatrogenic injuries during ear surgeries. This study aims to analyse the facial nerve's course and variations through the temporal bone, observing average morphometric values in relation to surrounding structures. Conducted at KLES Dr. Prabhakar Kore Hospital, Belagavi, this study utilized 25 wet cadaveric temporal bones obtained from fresh cadavers at J. N. Medical College. Dissections were performed to study the facial nerve's course and its variations, along with morphometric comparisons to other intratemporal structures. The greatest variation was found in the depth of the second genu, measured by adding the short process of incus to the spine of Henle and short process of incus to the second genu, ranging from 12.6 mm to 19.2 mm. The lengths of the mastoid (9.80 mm) and tympanic segments (5.71 mm) were relatively consistent. The processus cochleariformis was a reliable landmark for the tympanic segment. Isolated facial nerve anomalies are rare and typically occur with other middle ear developmental anomalies. Minute morphometric variations, however, can lead to iatrogenic injuries. While advanced imaging aids in identifying these variations, temporal bone dissection remains crucial for otologists to avoid injuries and address nerve pathologies effectively.