Tympanic cavity

We know very little about the pathology of the ear. And yet, hearing loss is a major component of cretinism. Old data summarized by Koenig (21) indicated that neurological endemic cretins present middle ear abnormalities characterized by hypertrophic bone changes of the promontorium, deformation of the ossicles, distorsion of the oval and round windows and thickening of the mucous membrane of the tympanic cavity. No data are available for the inner ear. 

Virtual Endoscopy (Clinical Applications) The Study of the Tympanic Cavity 141... 

As well as other anatomical districts, to generate three-dimensional (3D) reconstructions of the middle ear structures, a volumetric acquisition is required. In the case of the tympanic cavity, high-resolution computed tomography is the imaging... 

One interesting feature of SR or VR is to provide a global visualization of the aerated cavities of the middle ear. The reconstruction of the air content permits to estimate the grade of pneumatization of the tympanic cavity and mastoid cells that could change in the case of malformation and inflammation. 

The history of real endoscopy of the middle ear was started in 1967 by Zini when he tried to visualize the middle ear using a system of micromirrors, which allowed the exploration of the retrotympanum. This method, called indirect microtympanoscopy, is still used in clinical practice. Mer et al. (1967) introduced the fiberoptic endoscope into the tympanic cavity through a perforation of the tympanic membrane. Marquet and Boedts D (1975) described an endoscopic technique based on the use of a 1.7-mm... 

Transtympanic endoscopy can be used as a diagnostic tool or as guidance for otosurgical interventions. In the first case the easy access of the external auditory canal allows the visualization of the tympanic membrane, a barrier between the endoscope and the middle ear only the presence of a pathologic or surgical (miringotomy) perforation permits a limited exploration of the tympanic cavity. 

Creating an endoscopic perspective from the external auditory canal to look toward the middle ear, the tympanic cavity can be divided into four regions on the basis of endoscopic and surgical studies retrotympanum (posterior), epitympanum (superior), protympanum (anterior) and ipotympa-num (inferior). 

The retrotympanum represents more than one half of the posterior part of the tympanic cavity and includes the oval and round windows (Parlier-Cuau et al. 1998). VE allows displaying all the components of the retrotympanum (Fig. 10.2b) showing eminence and depressions, represented by pyramidal and styloid eminence, pyramidal ridge, ponticulus, subicu-lum, and eminence of the mastoid portion of the facial nerve (Pickett et al. 1995 Espinoza 1989). 

The promontory appears at VE as an eminence with a smooth surface that covers the round window. This opens from the tympanic cavity into the scala tympani of the cochlea. 

The protympanum represents the anterior part of the tympanic cavity that includes the pharyngo-tympanic tube. The superior border of the tube divides the protympanum from the sinus epitympani. The inferior border separates the tube from the internal carotid artery. The protympanum is easy to explore with either transtympanic endoscopy or VE (Fig. 10.2c). 

The ipotympanum represents the floor of the tympanic cavity, separated from the mesotympanum by a horizontal plane crossing through the inferior border of the external meatus. VEs display the floor, characterized by many osseous crests whose development is related with the dimensions of the sub-labyrinthic cells. 

Middle ear. Spaces of the tympanic cavity epitym-panum, mesotympanum, hypotympanum, Prussak s space, sinus tympani mastoid antrum. Promontory. Ossicles malleus (caput, collum, manubrium), incus (corpus, short and long crus, lenticular process-often only partly visible), stapes-best visible on paraxial images (anterior and posterior crus, caput-... 

Fig. 11.2a,b. Inflammation. Coronal MPR. Secondary cholesteatoma of the middle ear (a) with completely opacified tympanic cavity, destructed ossicles, small erosions along the walls of the tympanic cavity, and at the canal tympanic facial nerve segment (arrow), protrusion of the drum, soft tissue masses in the external auditory canal, reduced mastoid pnemiiatisation. 

The diagnosis was known at the time of CT. CT was performed to show the extent of the cholesteatoma. Otitis media chronica mesotympanalis (b). The tympanic cavity is opacified, too. The often reduced mastoid pneumatisation is not so pronounced in this case, there are no signs of bony destructions or erosions, and the drmii is retracted... 

CT is the method of choice in clinically suspected fractures of the temporal bone. Fracture lines, fragment dislocation, and potential complications (inclusion of the facial nerve canal, carotid canal, and roof of the tympanic cavity) can be unequivocally detected. In routine work, the traditional differentiation into longitudinal, transverse (Fig. 11.3), and mixed fractures is used despite newer classifications. As a result, the damage to the... 

Fig. 11.3a,b. Trauma. Axial MPR. Typical course of fracture lines (arrows) in a longitudinal (a) and transverse fracture (b). Opacities in the tympanic cavity and mastoid cells (a) are... 

Fig. ll.5a,b. Malformation. Axial (a) and coronal (b) MPR. Atresia auris congenita of middle degree-membranous atresia (star) and stenosis of the external auditory canal (EAC), hypoplasia of the tympanic cavity, reduced mastoid pneumati-... 

The inferior tympanic branch has certain distinctive features. This artery accompanies the tympanic branch of the 9th cranial nerve in the inferior part of the tympanic cavity, where it usually divides into three branches. The ascending branch anastomoses with the petrosal branch of the middle meningeal artery, accompanying the major deep petrosal nerve. An anterior branch joins the caroticotympanic artery, following the neural anastomosis between the tympanic branch to the ninth cranial nerve and the pericarotid nervous plexus. The posterior branch that courses towards the facial canal, where it anastomoses with the stylomastoid artery. 

Ear the entire human hearing apparatus, consisting of three parts middle ear or tympanic cavity, membrane and eustachian tube, and the inner ear or labyrinth. 

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