Cartilage interposition in ossiculoplasty with hydroxylapatite prostheses: a histopathologic study in the guinea pig

In this experimental animal study, a cartilage disk was interposed between a synthetic middle ear prosthesis and the tympanic membrane in guinea pigs to investigate its effect on the extrusion process of the implant. Two groups of guinea pigs were studied. One group consisted of animals in which the prosthesis was directly in contact with the tympanic membrane, and the other group consisted of animals in which a cartilage disk had been inserted between the head of the prosthesis and the tympanic membrane. Before histologic processing, in situ inspection was performed with an operating microscope. After fixation and embedding, light microscopic and transmission electron microscopic examination were performed. We studied the histopathologic aspects of the tympanic membrane with regard to the protrusion and extrusion processes of the middle ear implant. In this experimental model, protrusion and extrusion of a hydroxylapatite middle ear prosthesis was greatly reduced by interposition of a cartilage disk. Further clinical evaluation of these experimental results is needed in the human middle ear.     

Standardisierte Messungen der Schallübertragung verschiedener Mittelohrprothesen

The sound transmission properties of three different commercially available middle ear implants and the prototype of a complete middle ear prosthesis (CoMEP) were evaluated with a special measurement system that permits standardized conditions. This system uses a mechanical middle ear model (MMM) which approximates the impedances of the tympanic membrane and inner ear. The implants were fitted under defined conditions into the MMM. Displacement of the artificial stapes footplate of the MMM was measured with an optical probe. The measurements of different middle ear prostheses showed that the mass of the implant was the most important factor for optimum high frequency transmission. The lightest implant (4 mg, titanium) showed the best results. The CoMEP revealed the highest sensitivity because of a slight enlargement of the diameter of the artificial tympanic membrane. These findings show that the CoMEP is able to restore sound transmission to a normal range. In a second experiment one of the implants was fitted into the MMM with different forces. The increase of stiffness produced a slightly better high frequency transmission at the expense of low frequency sensitivity. Hence, the fitting of the implant may not be too stiff because of its loss of mobility within a significant frequency range.     

中耳机械模型的建立及听骨赝复物传音特性的研究

目的探讨对人工听骨赝复物传音功能进行评价的客观方法，以及钛金属人工听骨赝复物不同质量和不同顶盘面积在中耳机械模型中对传音功能的影响。方法用两块圆形的弹性膜分别代替鼓膜和前庭窗，两膜之间放置人工听骨，在人工外耳道侧给予纯音刺激，同时记录其声强，在前庭窗膜处用激光测振仪测量前庭窗膜的振动速度，通过比较振动速度的大小来比较人工听骨的传音特性；将质量不同和面积不同的2组钛人工听骨分别安放于中耳机械模型中测量其传音特性。结果模型感觉阈曲线和正常人听阈曲线对比，两者走势基本相同。钛听骨顶盘面积较小的听骨在1500-4000Hz其传音特性优于顶盘面积较大的听骨；质量小的听骨在高频区传音好，质量大的听骨在低频区传音比较好，但总体上质量小的听骨传音特性较好。结论中耳机械模型是检验人工听骨传音特性并进行人工听骨赝复物客观评价的理想工具之一；钛人工听骨的质量和顶盘的面积对其传音特性均有影响，在设计人工听骨时或手术要同时考虑到质量和顶盘面积对传音的影响。     

Pathogenesis of experimental aural cholesteatoma in the chinchilla

Histopathological observation of celloidin serial sections of the chinchilla middle ear after treatment with propylene glycol disclosed the development of severe inflammation of the middle ear mucosa and tympanic membrane, papillary proliferation of the epidermis of the tympanic membrane and external auditory meatus, and retraction and adhesion of the tympanic membrane. The findings for the tympanic membrane, impedance testing and histopathological examination suggested that there were two types of acquired cholesteatoma formation, probably with a difference in the pathogenesis. In one type, the proliferated epidermal layer of the tympanic membrane penetrated into the middle ear cavity making tympanic perforations. In the other type, there was progressive retraction of the tympanic membrane forming a retraction pocket. We discuss the two different patterns of cholesteatoma development.     

Middle ear sound transmission: a field of early interest to Merle Lawrence

Merle Lawrence, together with his teacher, E.G. Wever, made early contributions to the problem of middle ear sound transmission. Experiments were mostly done in cats and studied the effects of stepwise destruction of the middle ear on cochlear input and the effects of changes in middle ear air pressure on sound transmission. Their experiments provided the first physiologic evidence that the origin of auditory distortion lies in the inner ear, not in the middle ear. Lawrence also demonstrated a dual innervation of the tensor tympani muscle. With the aid of newer instrumentation, the authors studied the effects of alterations of the middle ear cavity configuration, stepwise removal of the middle ear structures, restriction of ossicular mobility, and ossicular mass loading. Our experiments caused partial decoupling of the tympanic membrane and distortion of the axis ligaments, the apparent weak elements of the middle ear system in cats. The placement of the prosthesis along the mallear handle did not affect sound transmission, as long as the connection between malleus and prosthesis was made inflexible.     

The effect of chronic middle ear inflammation on the pneumatization of the tympanic bulla in pigs

The effect of chronic middle ear inflammation on the pneumatization of the tympanic bulla was investigated in piglets. The pig tympanic bulla has an air cell system which is divided by trabeculae and closely resembles the human mastoid air cell system. The tympanic bulla and its air cell system in normal ears were well developed because of the bone formation and the bone resorption inside the cortex, whereas the tympanic bulla affected by chronic otitis media in the early stages of life exhibited retardation of pneumatization arising from the disturbed bone resorption by inflammatory stimulus. It was concluded that affliction with chronic middle ear inflammation in the early stages of life causes inhibition of pneumatization by hindering the development of the air cell system.     

Tympanometry

The basic principles essential for interpreting two-component, multiple frequency tympanograms first are reviewed. These principles then are applied to an analysis of tympanometric shape (conductance, susceptance, and admittance tympanograms) as a function of probe frequency in subjects with normal middle ear transmission systems. The final section presents tympanometric data from patients with confirmed middle ear pathologies that produce an increase in resonant frequency (e.g., middle ear effusion, otosclerosis, ossicular adhesions, and tympanic membrane retraction) or a decrease in resonant frequency (e.g., otitis externa, serous otitis media, tympanic membrane pathology, and ossicular discontinuity). The advantages and disadvantages of a particular probe frequency and/or admittance component are illustrated with individual cases. The cases further demonstrate that the same tympanometric pattern can be recorded from ears with different pathologies (e.g., tympanic membrane perforation with cholesteatoma, tympanic membrane retraction, ossicular adhesions, and middle ear effusion), and conversely, that the same pathology can result in different tympanometric shapes (e.g., tympanic membrane perforation, middle ear effusion, and otosclerosis). Caution, therefore, must be exercised in ascribing a tympanometric abnormality to a specific middle ear lesion.     

Etiologic factors in non-suppurative otitis media

Two observations in non-suppurative otitis media, namely the serous fluid and the tympanic membrane retraction, may have separate explanations as to the etiologic factors. The first is the obstruction of the collecting lymphatic tubules of the middle ear and eustachian tube as they drain to the retropharyngeal lymphatics. This leads to a transudation of fluid in the middle ear or serous fluid. The second observation, retraction of the tympanic membrane, may be due to an absence or significant reduction of the surface tension lowering substance (Surface Active Membrane) of the eustachian tube, preventing the transmission of air to the middle ear from the nasopharynx.     

Tympanic membrane/middle ear pathologic correlates in chronic otitis media.

OBJECTIVE: To correlate pathologic findings of the tympanic membrane with pathologic changes in the middle ear cleft in chronic otitis media. STUDY DESIGN: Retrospective. MATERIAL AND METHODS: One hundred-fifty temporal bones from 97 subjects with chronic otitis media (defined as middle ear pathologic changes including granulation tissue, fluid, cholesteatoma, cholesterol granuloma, tympanosclerosis, and ossicular changes) were selected to correlate the presence of these middle ear pathologies with histopathologic changes of the tympanic membrane. The tympanic membrane pathologies included perforation, myringosclerosis, retraction, hemorrhage, fluid-filled cystic spaces, or dilated vessels. Temporal bones were also assessed for atelectasis. Fifty-six normal temporal bones were taken as controls for measurements. RESULTS: Significant correlations between tympanic membrane and middle ear pathology included myringosclerosis and granulation tissue, myringosclerosis and ossicular pathology, retraction and cholesterol granuloma, retraction and cholesteatoma, retraction and ossicular pathology, perforation and ossicular pathology, and hemorrhage and granulation tissue. Additive effects of some pathologies were also observed. Almost half the bones with middle ear pathology had no associated tympanic membrane pathology, whereas multiple pathologic changes in the tympanic membrane generally showed underlying multiple pathologic changes in the middle ear. CONCLUSION: When tympanic membrane pathology is detected otoscopically, its presence, alone or in combination, can be a strong indicator of underlying middle ear pathology. However, a normal-appearing tympanic membrane does not exclude the possibility of middle ear pathology. These findings suggest the need for other diagnostic tools such as multifrequency tympanometry and otoacoustic emissions to complement otoscopy for diagnosis of middle ear pathology, especially in a tympanic membrane that appears "normal."     

Tympanometry and laser Doppler interferometry measurements on otitis media with effusion model in human temporal bones.

HYPOTHESIS: The aim of this study is to investigate the effect of middle ear fluid and pressure on tympanic membrane mobility by using laser Doppler interferometry and to compare these results with tympanometry. BACKGROUND: Tympanometry has been commonly used for evaluation of otitis media with effusion, a middle ear disease with fluid in the cavity. However, this test lacks specific interpretations of middle ear disorders based on tympanometric data. Laser interferometry, as an advanced research tool to measure middle ear function, may provide knowledge of how tympanic membrane mobility is affected by middle ear fluid and pressure. METHODS: An otitis media with effusion model was created in seven human temporal bones for conducting experiments with tympanometry and laser interferometry. Middle ear pressure varied from -20 to +20 cm water, and the amount of fluid in the middle ear was gradually increased to fill the cavity. RESULTS: The displacement of the tympanic membrane measured by laser interferometry at selected frequencies decreased significantly corresponding to the middle ear air pressure changes. Tympanometry detected middle ear pressure by the change of tympanometric peak location, but the tympanogram shape was not affected by the middle ear pressure. The middle ear fluid was detected by tympanometry with as little as 0.3 mL, and laser interferometry was able to measure the displacement change of the tympanic membrane with 0.2 or 0.3 mL fluid at different frequencies. CONCLUSION: Laser interferometry can detect the effect of middle ear pressure and fluid on tympanic membrane movement as well as tympanometry does.     

Cholinergic innervation of the guinea pig tympanic membrane.

While cholinergic nerve fibers of the parasympathetic system have been demonstrated in the middle ear mucosa, such innervation of the tympanic membrane has never been shown. Such fibers may prove important since the tympanic membrane may be one of the initial sites of effusion production, and since parasympathetic innervation is thought to be involved with middle ear effusion. To demonstrate cholinergic innervation, we have used modified direct thiocholine histochemical staining. Anesthetized Hartley guinea pigs were killed, and the tympanic bullae were removed intact, fixed in 4% paraformaldehyde, and then stained whole. Following staining, the tympanic membrane was dissected from each bulla and whole-mounted for light microscopy. Numerous acetylcholinesterase-positive fibers were observed on the tympanic membrane. Some fibers appeared to be vessel associated, although the majority did not. This suggests that these fibers may act on the mucosa or vasculature of the tympanic membrane and contribute to the pathogenesis of middle ear effusion.     

Combined effect of fluid and pressure on middle ear function

In our previous studies, the effects of effusion and pressure on sound transmission were investigated separately. The aim of this study is to investigate the combined effect of fluid and pressure on middle ear function. An otitis media with effusion model was created by injecting saline solution and air pressure simultaneously into the middle ear of human temporal bones. Tympanic membrane displacement in response to 90 dB SPL sound input was measured by a laser vibrometer and the compliance of the middle ear was measured by a tympanometer. The movement of the tympanic membrane at the umbo was reduced up to 17 dB by the combination of fluid and pressure in the middle ear over the auditory frequency range. The fluid and pressure effects on the umbo movement in the fluid-pressure combination are not additive. The combined effect of fluid and pressure on the umbo movement is different compared with that of only fluid or pressure change in the middle ear. Negative pressure in fluid-pressure combination had more effect on middle ear function than positive pressure. Tympanometry can detect the middle ear pressure of the fluid-pressure combination. This study provides quantitative information for analysis of the combined effect of fluid and pressure on tympanic membrane movement.     

Congenital Cholesteatomas in the Tympanic Membrane

The etiology of congenital middle ear (ME) cholesteatomas is unclear. One etiologic possibility of ME cholesteatoma may be progression of a congenital tympanic membrane (TM) cholesteatoma. We recently have encountered three cases of congenital tympanic membrane cholesteatoma. Each child, ages 1, 3, and 14 years, presented with cholesteatoma of the tympanic membrane extending into the middle ear. These children have not had previous otologic surgery including myringotomy, nor had they had repeated middle ear infections, perforation, or trauma. Neither the 3-year-old nor 14-year-old child complained of hearing loss. Audiograms demonstrated only a mild conductive loss. Each child underwent excision with tympanoplasty. Although the middle ear component of the cholesteatoma was always more extensive than the pearl seen, the point of attachment was the TM and not the middle ear. This demonstrates one possible source for congenital cholesteatomas.     

Temporal bone histopathology in chronically infected ears with intact and perforated tympanic membranes.

Chronic suppurative otitis media has been clinically defined as a chronic discharge from the middle ear in the presence of a perforation of the tympanic membrane. However, irreversible tissue pathology in the middle ear or mastoid can occur behind an intact tympanic membrane. One hundred forty-four human temporal bones with chronic otitis media were divided into two groups: those with perforated (28) and those with nonperforated (116) tympanic membranes. The histopathological findings of their middle ears were compared. Granulation tissue in various degrees was the most prominent pathological feature. It was observed in 96% of temporal bones with perforation of the tympanic membrane, and in 97% of those without perforation. Also found were ossicular bony changes (96% with perforation; 90.5% without), middle ear effusion (93% with perforation; 89% without), cholesterol granuloma (21% with perforation; 12% without), cholesteatoma (36% with perforation; 4% without), and tympanosclerosis (43% with perforation; 20% without). This study shows that the histopathological changes of the middle ear are similar in temporal bones with and without perforation of the tympanic membrane. The clinician should, therefore, be aware that an intact tympanic membrane does not necessarily preclude the presence of gross pathological changes of the middle ear cleft.     

Pulsion hernias of the tympanic membrane

A pulsion hernia of the tympanic membrane is an outwardly bulging, thin, atrophic area of the tympanic membrane. Those patients who develop pulsion hernias repeatedly autoinflate the middle ear and consequently maintain a positive middle ear pressure, which pushes the thin atrophic portion of the tympanic membrane laterally beyond the normal plane of the tympanic membrane. The thinness of the tympanic membrane over the pulsion hernia suggests that the herniation has developed through a pre-existing area of weakness where the fibrous middle layer has disappeared.     

Transient evoked otoacoustic emissions in patients with middle ear disorders

The aim of this study is to investigate the middle ear dynamic characteristics and their influence on TEOAEs in patients with middle ear disorders. The middle ear dynamic characteristics and TEOAE findings were investigated in 89 patients with middle ear disorders using the sweep frequency impedance (SFI) meter and the ILO88 system, respectively. These patients were divided into six subcategories: tympanic membrane aberrations, otitis media with effusion, chronic otitis media, tympanic membrane perforation, otosclerosis, and ossicular chain dislocation. Details of the TEOAE frequency characteristics were compared with the individual's middle ear dynamic characteristics. TEOAE status as a function of hearing threshold and middle ear dynamic characteristics was also examined. The results showed that the middle ear dynamic characteristics in patients with middle ear disorders correlated with the TEOAE frequency characteristics and amplitudes. The hearing level and middle ear mobility were the controlling factors affecting TEOAE status. Using both non-linear and linear stimulus modes, larger TEOAE responses were obtained when the hearing level was better than 20 dB HL, and there was moderately good middle ear mobility. Moreover, TEOAEs were absent using the non-linear mode when the hearing level was worse than 30 dB HL, whereas with the linear mode. TEOAEs were recordable even with hearing losses of up to 40 dB HL in patients with middle ear disorders. A higher incidence of recordable TEOAEs was found in the subgroups with tympanic membrane abnormalities and secretory otitis media when compared with the other subgroups. No TEOAEs were recordable in patients with chronic otitis media.     

Comparison of tympanometry and otomicroscopy during healing of otitis media

One hundred ears in 50 children with acute otitis media during healing were examined with tympanometry and the objective measures were compared with the subjective evaluation of otomicroscopy by four otolaryngologists independently. Tympanometric findings could more often correctly suggest reduced tympanic membrane mobility than did otomicroscopy, but both methods gave an equally good indication of middle ear effusion. However, otomicroscopy was necessary when evaluating the colour and the appearance of the tympanic membrane and revealed middle ear effusion in a few cases with 'normal' tympanometry. As a rule: normal tympanometry (Jerger type A) was closely correlated with a normal tympanic membrane and a normal middle ear without effusion; pathological tympanometry (Jerger type B) was accompanied by middle ear effusion and needed follow-up; ears with tympanometric pressure more negative than -150 mmH2O but more positive than a flat curve needed otomicroscopy to identify middle ear effusion.     

YAG-Nd laser: effects of radiation on acoustic analyser function in experimental animals]

Effects of laser radiation on the function of the internal ear receptors were studied using short-latent acoustic evoked potentials (SLAEP) of rabbit truncus cerebri. Contact laser impact in the area of the medial wall of the tympanic cavity in one of the ear was made after registration of baseline SLAEP. The other ear served control. It was found that YAG-Nd laser radiation had the receptor damage threshold within 7-8 W. Assessment of laser energy reaching receptors of the animals' labyrinth was carried out by the thickness of the bone of tympanic medial wall in the rabbit middle ear. Differences in the above thickness in humans and rabbits and calculated transmission factors for laser radiation of the bone tissues indicate that radiation power 14-16 W may appear critical in manipulations on human middle ear.     

Volumetric analysis of the tympanic isthmus in human temporal bones

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.