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Published in Joseph Manjaly, Peter Kullar, Advanced ENT Training, 2019
The tympanic segment (8–11 mm) accounts for the facial nerve between the first and second genu (marked by the pyramidal eminence). It courses on the medial wall of the middle ear deep to cochleariform process and over the top of the oval window to the pyramidal eminence. It has no branches within this section.
Anatomy
Published in Stanley A. Gelfand, Hearing, 2017
The middle ear contains two muscles, the tensor tympani and the stapedius (Figures 2.7 and 2.8). The stapedius muscle is the smallest muscle in the body, with an average length of 6.3 mm and a mean cross-sectional area of 4.9 mm2 (Wever and Lawrence, 1954). This muscle is completely encased within the pyramidal eminence on the posterior wall of the tympanic cavity, and takes origin from the wall of its own canal. Its tendon exits through the apex of the pyramid and courses horizontally to insert on the posterior aspect of the neck of the stapes. Contraction of the stapedius muscle thus pulls the stapes posteriorly. The stapedius is innervated by the stapedial branch of the seventh cranial (facial) nerve.
The Facial Nerve and its Non-Neoplastic Disorders
Published in John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed, Paediatrics, The Ear, Skull Base, 2018
Christopher Skilbeck, Susan Standring, Michael Gleeson
The tympanic segment is 8–11 mm long. It runs the length of the superior edge of the medial wall of the tympanic cavity, perpendicular to the long axis of the petrous part of the temporal bone, taking a posterior path that inclines downwards and laterally from the geniculate ganglion to the second genu at the level of the pyramidal eminence.34 Proximally it passes just above and medial to the posterior edge of the cochleariform process and the tendon of tensor tympani. The cochleariform process is a consistent landmark, when other landmarks are obscured or have been destroyed by pathology. More distally the nerve lies above the oval window niche, just anterior and inferior to the prominence of the lateral (horizontal) semicircular canal before bending at the second genu to enter the bony mass of the styloid complex. The second genu hugs the inferior aspect of the lateral semicircular canal; this relationship is extremely constant. The pyramidal eminence is a useful landmark for the second genu. The retrotympanum contains several small sinuses around the facial canal: the sinus tympani lies medial and anterior to the canal and the facial and lateral tympanic sinuses lie lateral and posterior to the canal.35–37 The distal aspect of the tympanic segment can be located surgically via a facial recess approach. The chorda tympani nerve and the fossa incudis can be used to identify the nerve when performing a facial recess approach. The second genu of the facial nerve runs inferolateral to the lateral semicircular canal (a relatively constant relationship). The posterior semicircular canal lies just posterior to the second genu: it also marks the superior end of the retrofacial air cells, which are helpful in delineating the medial aspect of the facial canal (Figure 112.5).
The role of computed tomography and magnetic resonance imaging for preoperative pediatric cochlear implantation work-up in academic institutions
Published in Cochlear Implants International, 2021
Art A. Ambrosio, Natalie Loundon, Daniel Vinocur, Peter Kruk, Hubert Ducou Le Pointe, Francois Chalard, Matthew Zapala, Daniela Carvalho
Radiologic metrics collected from all preoperative temporal bone CT scans included normality or anomaly of the following structures: vestibule, semicircular canals, facial nerve course, modiolus, round window, cochlea (i.e. normal appearing interscalar septum with 2.5 turns present), and jugular bulb (considered high-riding if extending above the basal turn of the cochlea). Further, measurements were employed to calculate the following: facial nerve recess (Figure 1, perpendicular distance from facial nerve to line parallel to EAC measured on axial images at level of pyramidal eminence), sigmoid sinus impingement (Figure 2, perpendicular distance of a line parallel to the EAC to the sigmoid plate), carotid canal distance (from edge of round window membrane to posterolateral margin of carotid canal), lateral mastoid space (Figure 3, perpendicular distance from line between cochlear promontory and junction of petrous and squamosal portions of the temporal bone to the superior lateral margin of EAC, measured on coronal image at level of the oval window), and maximal diameters on axial slices of the cochlear aperture, vestibular aqueduct, and internal auditory canal (IAC) to determine if abnormally sized. Logistic regression analysis was used to compare the categorical data groups with the intraoperative findings.
Location of the stapedius muscle with reference to the facial nerve in patients with unilateral congenital aural atresia: implication for active middle ear implants surgery
Published in Acta Oto-Laryngologica, 2020
Ryoukichi Ikeda, Hiroshi Hidaka, Takaki Murata, Tetsuaki Kawase, Yukio Katori, Toshimitsu Kobayashi
The SM is innervated by a branch of the FN. The SM fibers arise from the walls of the sulcus and converge into a round tendon, which passes anteriorly to emerge from the pyramidal eminence (8). Although the development of the SM was found to arise from the second pharyngeal arch [10], only a few previous reports have addressed the development of the stapedius muscle canal. Recently, Cisnerous reported that two areas of different embryological origin from the SM canal contains both the SM and FN [11]. An extension starts to grow from its caudal part at 11 weeks, which moves outwards and near to Reichert’s cartilage, forming the footplate and internal wall. The pyramidal eminence comes from the mesenchyme that surrounds the muscle, creating a partition to separate it from the laterohyale portion of Reichert’s cartilage. The SM and FN start to separate using a bony partition at 35 weeks, but dehiscence may degrade this separation [11]. Combined with these embryological findings, our results suggested that the development of the SM could be normal whereas the spatial relationship between the SM canal and FN may be changed after 35 weeks in CAA patients. Further histological studies are needed to understand the development of the SM in CAA patients.
Two cases of congenital stapes malformation: Implications for development of the stapes footplate and the oval window
Published in Acta Oto-Laryngologica Case Reports, 2020
Hiroki Ishida, Takayuki Okano, Yasuyuki Hayashi, Koji Nishimura, Tatsunori Sakamoto, Norio Yamamoto, Koichi Omori
We have discussed two cases having a stapes anomaly with absence of the stapes footplate and a patent oval window covered with mucosal membrane. The crura were attached to the promontory and the stapedius tendon was present, connecting the stapes superstructure and the pyramidal eminence in both the cases. These findings suggest that the formation of the oval window is independent from the development of the stapes footplate.