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Objectives: An anatomical study was performed to describe the endoscopic anatomy and variations of the protympanum, including classification of the protiniculum and subtensor recess., Methods: A retrospective review was conducted of video recordings of cadaveric dissections and surgical procedures, which included visualisation of the protympanum, across 4 tertiary university referral centres over a 16-month period. A total of 97 ears were used in the analysis., Results: A quadrangular conformation of the protympanum was seen in 60 per cent of ears and a triangular conformation in 40 per cent. The protiniculum was type A (ridge) in 58 per cent, type B (bridge) in 23 per cent and type C (absent) in 19 per cent. The subtensor recess was type A (absent) in 30 per cent, type B (shallow) in 48 per cent and type C (deep) in 22 per cent., Conclusion: The protympanum is an area that has been ignored for many years because of difficulties in visualising it with an operating microscope. However, modern endoscopic equipment has changed this, providing detailed anatomical knowledge fundamental to ensuring the safety of endoscopic surgical procedures in the region.

In order to improve realism in middle ear (ME) finite-element modeling (FEM), comprehensive and precise morphological data are needed. To date, micro-scale X-ray computed tomography (μCT) recordings have been used as geometric input data for FEM models of the ME ossicles. Previously, attempts were made to obtain these data on ME soft tissue structures as well. However, due to low X-ray absorption of soft tissue, quality of these images is limited. Another popular approach is using histological sections as data for 3D models, delivering high in-plane resolution for the sections, but the technique is destructive in nature and registration of the sections is difficult. We combine data from high-resolution μCT recordings with data from high-resolution orthogonal-plane fluorescence optical-sectioning microscopy (OPFOS), both obtained on the same gerbil specimen. State-of-the-art μCT delivers high-resolution data on the 3D shape of ossicles and other ME bony structures, while the OPFOS setup generates data of unprecedented quality both on bone and soft tissue ME structures. Each of these techniques is tomographic and non-destructive and delivers sets of automatically aligned virtual sections. The datasets coming from different techniques need to be registered with respect to each other. By combining both datasets, we obtain a complete high-resolution morphological model of all functional components in the gerbil ME. The resulting 3D model can be readily imported in FEM software and is made freely available to the research community. In this paper, we discuss the methods used, present the resulting merged model, and discuss the morphological properties of the soft tissue structures, such as muscles and ligaments.

In students' dissection practice, it is very difficult to teach students the structures and functions of the middle ear ossicles. The middle ear ossicles are too small to explain their structures and functions. Models are useful in explaining these points, but there have been no models that accurately explain the movements of the middle ear ossicles and the functions of the muscles in the middle ear. This time, we have made a model of middle ear ossicles. Our ear ossicles are made of paper-mache with metal in it. The incudomalleolar and incudostapedial articulations are made of rubber. The tensor tympani and the stapedius muscles are made of wire and the two wires can be fixed by cord stoppers. Our model explains clearly the following mechanisms of the middle ear ossicles. 1. The mechanism of sound conduction system. When the sound vibrates the tympanic membrane, malleus and incus rotate together. The long process of the incus pushes the head of the stapes. The sound is amplified by leverage. 2. Attenuation of sound by contractions of tensor tympani and stapedius muscles. When a loud sound is transmitted through the ossicular system, the tensor tympani muscle pulls the malleus inward while the stapedius muscle pulls the stapes outward. These two forces oppose each other and increase rigidity of the ossicular system, thus reducing the ossicular conduction. 3. The mechanism of how paralysis of stapedius muscle, caused by an injury to the facial nerve, results in hyperacusis. 4. This model also suggests a possible reason why the pars lucida of the tympanic membrane exists.

This study was designed to aid experimental otologic studies of the rat middle ear. The topographic anatomy of the albino rat middle ear is described. A set of microphotographs with matching illustrations presents the structural details at several surgical exposures. Anatomic differences between the rat, guinea pig, and cat are noted.

The epitympanic compartments and the anatomy of the atticotympanic diaphragm were examined in a pair of serially sectioned temporal bones with secretory otitis media and chronic otitis media, respectively. Findings confirmed reports of 19th century scientists in that Prussak's space has a wide connection to the mesotympanum through the posterior pouch of Tröltsch and may have an additional narrow passage in its roof to the lateral malleal space. The lateral incudomalleal fold regularly separates the upper lateral attic from the lower lateral attic and the mesotympanum. The medial incudal fold as a rule is atrophic already at birth. The anterior tympanic isthmus thus extends from the tensor tympani tendon to the posterior incudal ligament and is the main passage for epitympanic and mastoid aeration. Opening(s) in the tensor fold, when present, are also important. In some ears, the posterior tympanic isthmus may form an auxiliary narrow route for aeration via the incudal fossa. The isthmi may be blocked by middle ear infection, which can lead to chronic mastoid and attic disease. Pathways for cholesteatoma spread in the epitympanum are discussed.

On the basis of functional questions, graphic three-dimensional reconstructions of the tympanic bulla of the rat were made to gain insight into the spatial organisation of the contents of the bulla and especially of the tympanic membrane--ossicular chain--middle ear muscle complex. For this purpose drawings of microscopical sections of complete bullae were fed into the computer to make three-dimensional graphic reconstructions with hidden line removal. From these reconstructions plastic representations were made by the medical artist. The topographical anatomy of the tympanic bulla is discussed in detail and compared to the anatomy of the middle ear in man. It is postulated that, despite differences in spatial organisation of the middle ear of the rat compared to that of man, the middle ear muscles influence the ossicular chain in a comparable way. On the basis of the topographical anatomy it is feasible that the muscles in the rat act synergistically in increasing the stiffness of the ossicular chain.

Electromyographic recordings of the activity of the tensor veli palatini, tensor tympani, and stapedius muscles were obtained from several adult human subjects. Muscle responses were recorded under four stimulus conditions, ie, contralateral intense wide-band noise, air jet to the eye, swallow, and electrical stimulation of the tongue. The results indicated that the two tensor muscles responded to the same stimuli in similar patterns. The latter muscle differed from the response of the stapedius.

Middle ears (515) from 26 species of the rodent family Heteromyidae - genera Dipodomys, Microdipodops, Perognathus, and Liomys - were studied both grossly and histologically, for qualitative and quantitative comparisons. Middle ear modifications characteristic of each genus are qualitatively described. Quantitative comparisons are made among the 26 species in the study. Some correlations between middle ear size and other measurements are discussed. The middle ear is an acoustical transformer that for best efficiency must match the impedance of the cochlea to the impedance of the air in the external auditory meatus. It accomplishes this by a pressure increase and a velocity decrease through the combined effects of the lever and areal ratios; however, because the important consideration is a matching of two impedances rather than an absolute pressure increase, the pressure transformer ratio is a less informative measure of the middle ear's efficiency than is the impedance transform ratio. The impedance transformer mechanism is explained (from a morphological point of view), and equations are presented. Dipodomys, Microdipodops, and Perognathus have a theoretical transmission (at the resonant frequency) of 94-100% of the incident acoustical energy; Liomys, 78-80%. The areal ratio of stapes footplate to 2/3 tympanic membrane is remarkably constant among the species, varying only from 0.04 to 0.07: in Dipodomys and Microdipodops this small ratio is due to the very large tympanic membrane; in Perognathus and Liomys it is due to the extremely small stapes footplate. The lever ratio of incus to malleus varies from 0.28 to 0.33 in Dipodpmys and Microdipodops, from 0.37 to 0.46 in Perognathus, and from 0.55 to 0.60 in Liomys. In addition, the middle ear volumes and the morphology of tympanic membrane, ossicles, ligaments, and muscles, all combine to minimize both mass and stiffness. All these data suggest middle ear mechanisms which are very efficient over a broad frequency range. The middle ear modifications found in heteromyids are adaptive in predator avoidance, especially in areas of little natural cover; nevertheless, contrary to expectations, there is no firm relationship between habitat and the extent of these modifications in the 26 species. However, environment did apparently plan an important role in the evolution of the family, and this is discussed.

A volumetric study on the tympanic isthmus and its relationship to temporal bone pneumatization was conducted in 110 serially sectioned temporal bones with and without middle ear pathology. With a microcomputer and digitizing tablet, the area of the tympanic isthmus and the degree of pneumatization in sample sections were calculated. Nonpathologic temporal bones showed a significant correlation between the volume of the tympanic isthmus and the degree of pneumatization. The narrowest area of the tympanic isthmus and the degree of pneumatization were also highly correlated. The result indicated a definite inhibition of pneumatization due to chronic middle ear infection when compared with nonpathologic temporal bones.

A brief illustrated atlas demonstrates the progressive relationships of the anatomical structures of the cat's middle ear as one dissects these from the attic approach. There was an attempt to demonstrate the nerves of the lateral semicircular canal and the utricle but without preserving the footplate of the stapes to afford an unobstructed view of the nerves. For the first time, the anatomical features of the cat's middle are are brought together in a progressively illustrated and single source.

The relationships among the paratubal muscles were studied in human fetal and adult Eustachian tubes. That which has, in recent years, been labeled the tensor veli palatini muscle actually consists of two distinct groups of muscle fibers: a medial group, henceforth termed dilatator tubae, and a lateral group, called tensor veli palatini. The latter was found to have no Eustachian tube origin, but was continuous superiorly with the tensor tympani muscle. The dilatator tubae muscle was found to have a tubal attachment. The participation of this muscle system in the normal functioning of the Eustachian tube-middle ear system in man, and the problems inherent in the development of animal models simulating the physiology of the physiology of the human system, are discussed.