The tympanic segment of the facial nerve: Anatomical study

Abstract

There is a conroversy in the literature about the length of the proximal tympanic segment of the facial nerve (PTSFN). The objective of the current study is to measure the length of the tympanic segment of the facial nerve (TSFN) and of its proximal (PTSFN) and distal (DTSFN) segments, in normal human temporal bones. Moreover, we will explore if these lengths are correlated. If a form of a functional relationship can be established, it could offer insights in partially predicting or estimating the length of the TSFN as well as of its proximal and distal portions. Direct measurements were obtained in 40 normal human temporal bones, which were examined by surgical dissection. Relationships between these measurements were established using Pearson's correlation method (two-tailed). The length of the TSFN was on average 10.97 mm. The length of the PTSFN was on average 5.25 mm and of the DTSFN was 5.72 mm. No significant statistical differences according to gender or side (right or left) were detected. It was determined that the length of the TSFN was in linear correlation with positive direction with its proximal (PTSFN) and distal (DTSFN) segments. Also the PTSFN length was in linear correlation with positive direction with the DTSFN length. The length of the PTSFN comprises about one-half of the TSFN length. The existence of a definite correlation between the lengths of the TSFN, PTSFN, and DTSFN implies the existence of a form of functional interrelationship. This could facilitate prediction and identification of the TSFN and PTSFN lengths from the easily identifiable DTSFN length during surgery.

Surgical Anatomy of Facial Nerve for Revision Transmastoid Surgery

“…8 By transmastoid approach, the most commonly used structure to identify the geniculate ganglion is the cochleariform process. 9 We used the cochleariform process and also the tympanic ostium of the eustachian tube as landmarks for the geniculate ganglion.…”

“…[9][10][11][12][13][14][15] In addition, we measured the distances between the round window niche, the tympanic opening of the eustachian tube, and the tympanic segment because most of these structures can be observed during revision surgery of the middle ear. The angle of the second genu, the depth of the mastoid segment, and the distances between the sigmoid sinus and the mastoid segment are compatible with the current data in the literature.…”

Neuroanatomical correlation of the House-Brackmann grading system in the microsurgical treatment of vestibular schwannoma

“…63 The tympanic portion begins at the geniculate ganglion where the nerve abruptly turns 90° to run posteriorly and inferiorly to form the external genu. 69 The length of this section of the nerve is approximately 12 mm and is above the oval window and below the prominence formed by the horizontal semicircular canal. 23 The final segment of the facial nerve in the fallopian canal is the mastoid or vertical portion, which begins with a less abrupt bend, called the pyramidal turn, in which the nerve passes below the semicircular canal to descend behind the pyramid.…”

Time‐saving and fail‐safe dissection method for vestibulocochlear organs in gross anatomy classes

“…The vestibulocochlear organs are very small and have a unique morphology. They are embedded in the petrous part of the temporal bone (Berkovitz et al, ; Rask‐Andersen et al, ) with some variations (Miller and Pensak, ; Nikolaidis et al, ; Singla et al, ). They cannot be seen from the temporal bone surface.…”