Tympanic mucosa after tubal obstruction

Immunologic aspects of otitis media

The middle ear cleft is a modified gas pocket which functions normally when the gas contents are regulated by a normal eustachian tube, resulting in equalization of middle ear pressure to that of the environment. The most important regulator of this middle ear pressure is the eustachian tube, a critical passageway from the nasopharynx into the middle ear. Any alteration of eustachian tube mucociliary function caused by virus, allergy, pollutants, or alteration of the normal homeostasis of the nasopharynx will result in eustachian tube obstruction. This, in turn, leads to underventilation of the middle ear, and transudation of fluid. If bacteria or virus or viral-bacterial interaction leads to infectious disease of the middle ear, an immune response is produced as a result of the inflammatory response, allowing lymphocytes and antigen-presenting cells to enter into the middle-ear mucosa. This article summarizes the immunologic reactivity in the middle ear following a viral-bacterial inflammatory reaction in the middle-ear mucosa. Although secretory IgA is critical for protection of the nasopharynx, its function in the middle ear has still not been resolved. The evidence strongly suggests that IgG1 and IgG3 subclasses are responsible for eradication of middle ear pathogens. Finally, a review of alternative approaches to the prevention of otitis media is briefly discussed in this critical period of emergence of resistant bacteria to available antibiotics.

Displacement of the gerbil tympanic membrane under static pressure variations measured with a real-time differential moire interferometer

It is thought that chronic middle ear disease ultimately causes changes in the stiffness and elasticity of the tympanic membrane, but it is unknown whether such changes occur early in the course of the disease. In order to analyze mechanical changes in different parts of the tympanic membrane, a full field moire interferometry technique was utilized to measure the shape and real-time displacement in response to positive and negative pressure gradients applied across the tympanic membrane. The measurements were performed on fresh isolated temporal bones from the Mongolian gerbil. In order to gain sufficient visual access to the pars tensa for the moire measurements, the tympanic bulla was opened, the tensor tympani muscle and the incudo-stapedial joint were cut, and part of the medial wall of the tympanic cavity was removed. The malleus and incus and their ligaments were kept intact. The specimens were kept continuously humidified with an evaporator or in a humid chamber, since otherwise the tympanic membrane dries out in a few minutes when its medial surface is exposed. This desiccation reduces the elasticity and cause shrinkage which results in a reduction of the height of the cone constituted by the pars tensa. Profiles of the tympanic membrane at rest and under different pressure conditions were extracted from the moire interferograms. The tympanic membrane and ossicular complex exhibit a hysteresis effect as differences in the displacement patterns under identical pressure gradients during the loading and the unloading phase; a residual displacement of the pars tensa was for instance seen after the pressure gradient across the tympanic membrane was eliminated.

Distribution of mast cells in the tubotympanum of guinea pigs

The distribution pattern of mast cells in the middle ear mucosa and eustachian tube was examined histologically in adult and developing guinea pigs. The aim was to better understand the role of mast cells in the middle ear defense mechanism. The density of mast cells was highest in the pharyngeal orifice of the eustachian tube, and decreased in the direction of the tympanic orifice. The density was higher in adults than in developing animals. Mast cells were also found in the tubotympanic membrane of the fetal guinea pig. Mast cells in the middle ear mucosa appeared in areas covered by ciliated epithelia or areas richly vascularized. Almost all mast cells found in the middle ear and eustachian tube mucosa were the connective tissue type. The results of this investigation suggest that mast cells distribute in the tubotympanum in response to continuous stimuli to the tubotympanic cavity.

Changes of middle ear mucosa in secretory otitis media treated with ventilation tubes

The present study was designed to obtain the precise ultrastructural status of the middle ear mucosa of patients to whom ventilation tubes were applied for the treatment of secretory otitis media (SOM). This study comprised 14 children with SOM aged 5-11. Normal epithelium obtained from otosclerotic patients as controls was composed of three main cell types; basal, ciliated, and secretory. Electron microscopic observations revealed that ciliated cells were almost completely absent in the epithelium of patients with SOM. Secretory cells, on the other hand, were noted to be increased in number with cytoplasmic features indicating active secretory phase; abundant secretory granules in these cells featured both serous and mucoid characteristics. Following the application of ventilation tubes, the micrographs exhibited a vast number of ciliated cells. Furthermore, the secretory cells were less conspicuous and the secretory granules were mostly serous in type. The ultrastructural findings of this investigation strongly suggest that the application of ventilation tubes in cases of SOM stimulates ciliated cell regeneration, inhibits secretion of mucoid material, and activates serous secretion; all of which eventually shorten the recovery period.

Experimental otitis media with effusion induced by intratympanic lipid A instillation

Otitis media with effusion was induced in guinea pigs by intratympanic instillation of lipid A, the lipid moiety of gram-negative bacterial lipopolysaccharide from Salmonella minnesota Re595. Lipid A was chosen as an inducer because of its similar composition among various bacterial species. Animals were killed from the first to 14th day after instillation of various concentrations (0.2, 2, 20, 200 micrograms/ml) of lipid A in 0.5% triethylamine. By 3 days after instillation, all experimental animals developed serous middle ear effusion. The histologic findings included hemorrhage, mucosal edema, capillary engorgement, and migration of infiltrative cells including macrophages, polymorphonuclear neutrophils, and lymphocytes. These findings were most prominent 3 days after instillation, and the recovery of the middle ear epithelium was observed within 14 days. Repeated instillation of lipid A (2 micrograms/ml) at an interval of 14 days reinforced the local response accompanied by serous middle ear effusion. These findings indicate that lipid A can induce the inflammatory changes with middle ear effusion and that lipid A plays an important role in the pathogenesis of otitis media with effusion.

The structure of the middle ear epithelium of the rat and the effect of Eustachian tube obstruction

The middle ear cavity of the rat is lined with ciliated and squamous epithelium. The arrangement of the ciliated cells, interspersed with secretory cells, in distinct tracts and their continuity with the ciliated epithelium of the Eustachian tube, suggests the existence of a mucociliary transport system for cleaning the middle ear cleft. The secretory cells produce either neutral or sulphated glycoproteins, dependent on their location. In addition to these secretions, the epithelium of the lower part of the Eustachian tube is bathed with secretory products of seromucous glands. Also in the areas with squamous epithelium, numerous small secretory cells, the character of which is only identifiable with the electronmicroscope, are present. It is concluded that the middle ear lining can be considered as a locally modified respiratory epithelium. Blockade of the mucociliary transport system, supposedly a crucial aetiological factor in secretory otitis media, by obstruction of the Eustachian tube, induces pathogenic behaviour of microorganisms normally present in the middle ear. This results in either a transient or a longstanding infective middle ear disease, associated with a large variety of changes of the mucosa, especially with respect to the secretory activity. The data obtained indicate that the increased secretory activity encountered in secretory otitis media cannot be attributed to the isolated effect of tubal occlusion, but rather to an infective process.

Experimental long-term tubal occlusion in cats. A quantitative histopathological study

Unilateral tubal occlusion was performed in 10 cats, which were sacrificed 26-44 months later. During the observation period repeated bilateral tympanometry and auditory nerve response were recorded. Paracentesis with evacuation of effusion was performed up to eight times and the effusion was examined by viscometry. After sacrifice, quantitative histopathology of the bulla with determination of goblet cell density was carried out. In three ears having glue at the last paracentesis, the histopathologic changes were more pronounced than in the four ears having thin effusion. Three ears were dry at sacrifice with normal tympanometry, the histopathological changes evidently demonstrate the the normalization of the middle ear mucosa. The experiments demonstrate the great importance of tubal patency or function in prognosis of the disease. In ears with anatomically occluded tubes, no recovery occurred, whereas in ears with normalized tubal function, the middle ear mucosa and goblet cell density also normalized. Pathogenic and etiological aspects of secretory otitis are discussed.

The mucoperiosteum of the middle ear in experimentally induced sterile otitis media

The effect of Eustachian tube obstruction has been studied in germ-free rats. This model proved to be a reliable approach by which to study the isolated effect of tubal occlusion without the interference of infection. The effects on the middle ear structures are characterized mainly by stratification and hyperplasia of the epithelium, a transient increase in the periosteal activity, tympanosclerotic-like changes and accumulation of cholesterol in the middle ear fluid. No increase in the number of secretory elements could be registered during an observation period of 2 years.

Deviation with increasing age in histologic appearance of submucosal glands in human eustachian tubes

74 tubal specimens from the temporal bones of 37 autopsy cases of various ages (8 fetuses, 12 children, 4 young adults, 36 middle-aged adults, and l4 elderly adults) were examined histologically to study the deviation with increasing age in the submucosal glands of Eustachian tube. The tubal glands consisted of acini (terminal secretory portions) and three duct systems (intercalated, striated and excretory ducts). Cytologically, they were of the mixed type with crescents. It was observed that the mucous acinar cells were predominant in children, as compared with the serous acinar cells. These latter increased prominently in middle age, accompanied by a decrease in the number of mucous cells. Among the elderly, both types of acinar cells decreased and tended to be atrophic. On the other hand, oncocytic changes of the ductal epithelia were discovered in the pharyngeal part of Eustachian tubes of subjects over 60 years old. These aging changes may play an important role in the pathophysiology of patency and excretory processes of the Eustachian tube.

Studies on the production of middle-ear effusion in the experimental animal

Middle-ear effusions have been produced following eustachian tube obstruction in guinea pigs. This was achieved by plugging the pharyngeal office of the tube by an atraumatic lateral transpalatal incision. General anaesthesia was used throughout the entire procedure. The presence of fluid in the middle-ear cavity was determined by observing: (a) The appearance of pallor of the drum. (b) Retraction of the tympanic membrane. (c) Cloudiness of the tympanic bullae on radiographs obtained at weekly intervals, confirmed by: (d) Subsequent myringotomy. Serial smears of the induced effusions showed an absence of chronic inflammatory cells except in the case of one animal which developed bacterial otitis media. The presence of secretory cells was demonstrated in the actual epithelial layer and lamina propria but no discrete glands were found. Squamous metaplasia of the lining of the middle-ear cleft was noted. The fluid from the tympanic cavity appeared watery, faintly turbid and non-mucoid, and resembled the serious type of effusion found in man.

Experimental tubal obstruction. Changes in middle ear mucosa elucidated by quantitative histology

Two and 4 weeks after experimental tubal occlusion in germ-free rats the goblet cell density in the middle ear was increased, compared with the normal contralateral side, indicating that transformation of epithelial cells to secretory cells can occur without infection. Other histopathological changes such as vasodilatation, oedema, round cell infiltration, fluid uptake of epithelial cells (which were thereby distended), hyperplasia of the epithelial cells, formation of intra-epithelial glands and some few subepithelial glands, are described. The finding may indicate that negative middle ear pressure and fluid uptake into the cells damage the epithelium, and the succeeding processes may be regarded as reparative processes following the epithelial damage.

Pathogenesis and pathology of chronic secretory otitis media

Secretory otitis media is divided into three stages, and the pathogenesis and pathology of each stage are described on the basis of quantitative histopathological studies. In the initial stage, ie, the period before accumulation of mucus in the middle ear, metaplasia causes a transformation of the mucosa into a secretory mucosa and mucous glands are formed. These processes are described in detail. In the secretory stage, which is the period with accumulation of mucus in the middle ear, an enormous increase was found in the density of goblet cells and the density of active mucous glands was large. In the degenerative stage, the production of secretion abates owing to degeneration of the glands. These become inactive, and the mucosa gradually normalizes. The normalization process is slow and runs through several turnover periods of the epithelium by means of a gradually decreasing rate in the division of the basal cells.

Cells involved in the middle ear defense system

Despite the high incidence and prevalence of otitis media, its pathogenesis is not thoroughly understood. In the last decade, many efforts have been made to provide a better understanding, and abundant information has become available. At the same time the field of immunology has advanced at an extremely rapid pace. We have followed the gradual cellular events in the defense reaction of the middle ear, utilizing eustachian tube obstruction to induce otitis. Seventy-five cats were divided in groups and sacrificed at intervals between one day and six months, and their temporal bones were studied. During an initial phase of inflammation, polymorphonuclears appear at three days in connective tissue; at the same time active fibroblasts synthesize tropocollagen and ground substance while epithelial cells secrete mucus and lysozymes. These cells, together with those involved in the mucociliary transport system and a patent functional eustachian tube, constitute the nonspecific system of defense. The transition cells are the macrophages which appear at one week to interact with T and B cells to produce the specific immune response. Plasma cells appear at two weeks to peak at one month with synthesis of immunoglobulins A, G and M. A secretory immune system is observed. At three and six months, lymphocytes are the predominant cells and occasional accumulations of mononuclears are observed. The reaction involves the entire middle ear, including mucoperiosteum, middle ear muscles and round window membrane. We believe that a better understanding of the middle ear defense system will lead in time to a practical clinical assessment of the immunological status during the evolution of each particular process or disease involving the middle ear, and a more rational approach to the treatment and, hopefully, prevention of chronic ear disease.

Twenty-five years of tympanoplasty: a critical evaluation

Twenty-five years of experience with tympanoplasty have demonstrated that the operation is not as safe as it is generally thought. Serious complications do occur. Many problems of middle ear reconstruction remain unsolved and more often than not results have not withstood the test of time. This paper attempts to answer the following questions. 1) What are the hazards in tympanoplasty surgery? 2) What are the complications of tympanoplasty? 3) What can tympanoplasty do for the welfare of the patient with reasonable certainty? 4) What has tympanoplasty been unable to do in spite of continued attempts and experimentation? 5) Why is tympanoplasty successful or unsuccessful in seemingly similar cases?

Goblet cell population in the pathological middle ear and eustachian tube of children and adults

On 64 temporal bones from slightly abnormal and pathological prematures and newborn infants, children, and adults, 35,000-40,000 counts of goblet cells were done in different parts of the Eustachian tube and middle ear. The goblet cells were present in all Eustachian tubes and middle ear areas. In ears previously exposed to infection the density was slightly increased in the tubal orifice and in most parts of the middle ear. In subacute and acute pathological actions, especially tubal occlusion, and chronic diseases, such as active chronic otitis and in secretory otitis media, the goblet-cell density is appreciably increased.

Fine structures of the normal mucosa in developing rat middle ear

Forty-two fetal and 90 developing young rats were studied electron microscopically to obtain a normal cellular distribution pattern of middle ear mucosa. The results showed that while ciliated columnar or cuboidal cells interspersed with secretory cells were predominantly distributed around the tympanic orifice and transitional zone, cuboidal or squamous nonciliated cells without secretory granules were numerous in the remaining part of the bulla. Development of ciliated cells started at the 17th or 18 th fetal day,paralleling that of secretory cells. The number of ciliated and secretory cells increased rapidly after birth. Glands were not found in the osseous tube, tympanic orifice, or other portions of the middle ear cavity in fetal, newborn, or suckling rats, while they are abundant in the cartilaginous portion of the tube. The findings of this study indicate that both secretory and ciliated cells are normal components of middle ear mucosa although these cells are restricted to the tympanic orifice and transitional zone, and that the mucociliary defense system starts to develop during the fetal stage.

Secretory otitis. Histopathology and goblet-cell density in the Eustachian tube and middle ear in children

The histological changes in the middle ear of four children with incipient or mild chronic secretory otitis are described. They consist in vascular dilatation and proliferation, round-cell infiltration, epithelial metaplasia into pseudostratified, columnar, ciliated epithelium posteriorly in the middle ear, formation of abnormal mucous tubular glands, and an increase in goblet-cell density in the osseous tube and middle ear. The causes of these changes were presumably long-lasting tubal occlusion due to a permanent nasogastric tube and protracted catarrhal diseases. The density of goblet cells was determined in various parts of the Eustachian tube and middle ear. The findings were analysed statistically and compared with the density in prematures and newborns, normal children, and normal adults. In the tympanic orifice and in the osseous Eustachian tube the goblet-cell density was greatly increased, whereas the increase in the middle ear varied individually, but was in conformity with the other findings. These cases illustrate that the histopathological changes in the middle-ear mucosa in secretory otitis must be regarded not only from a qualitative, but certainly also from a quantitative point of view.

Primate model for studies of clinical problems of middle ear functions

Eustachian tube and middle ear function has been studied in the acute and chronically prepared Rhesus monkey preparation. Measures have included observations of tympanometry and input impedance of the middle ear, of transmission of energy through the middle ear, of static middle ear pressure and of threshold and suprathreshold hearing. Positive and negative long and short-term static middle ear pressures, the effects of middle ear fluids, and various aspects of Eustachian tube function in both normal and pathologic preparations have been studied. In general our observations indicate that the Old World monkey may provide a model permitting acquisition of quantitative data of a variety of middle ear functions under carefully controlled laboratory conditions, including those requiring measures simply not possible in man.

Role of perilymph in the early stage of serous otitis

After injection of an electron-dense tracer into the cerebrospinal fluid (CSF) the particles can be seen within the lymphatic spaces of the middle ear mucosa after a few minutes. They find their way via the well known communication routes from CSF to the perilymphatic spaces of the inner ear. From there they enter through open fluid spaces into the fibrocytic network of the round window membrane which stands in open relationship to the extracellular fluid spaces of the middle ear mucosa. They were drained to the regional lymph nodes by lymphatic vessels. When inducing a serous otitis by experimental obstruction of the Eustachian tube it could be demonstrated that the fluid within the middle ear cavity is partly coming from the CSF and perilymph. Later the healing process of the middle ear epithelium was studied after the onset of serous otitis with and without artificial ventilation of the middle ear.

Experimental middle ear effusions: an immunofluorescent study

Immunological phenomena occurring in the mucosa of the middle ear and Eustachian tube were investigated following experimental tubal obstruction which produced middle ear effusions in squirrel monkeys. Although there are many variations among specimens, in general all classes of immunoglobulin-producing plasma cells have shown an increase in number and/or an increase in intensity of fluorescence. IgG and IgA-producing plasma cells were more prominent than those producing other immunoglobulins. Presence of IgA in the secretory epithelial cells of the Eustachian tube of normal monkeys further supports the concept that the middle ear and Eustachian tube in the monkey as in human are protected by an immunodefense system.

Functional morphology of the lining membrane of the middle ear and Eustachian tube: an overview

A large part of normal middle ear cavity and Eustachian tube is provided with a mucociliary transportation system which is considered the first line of defense of the middle ear. Secretory cells of the normal mucosa of the middle ear and the tube can be classified into three main types: mucous, mixed and dark granulated (or serous). This may mean that the secreta of the mucosa is biochemically diverse and/or in a dynamic state. The presence of immunoglobulin-producing plasma cells (IgA, IgG and IgM) and macrophages in the Eustachian tube and the middle ear mucosa supports the concept that the middle ear is protected by an immunologic defense system. Normal mucosal epithelial cells of the middle ear and the tube possess the ability to transport macromolecules by intact epithelial cells toward connective tissue layer where the macromolecules are either phagocytized by histiocytes or enter into capillary system. The macrophages of regional lymph nodes also picked up the macromolecules. Demonstration of lamellar substances similar to phospholipids in the secreta of the tube and middle ear mucosa of the guinea pig suggests the presence of auditory surface-active agent(s) (surfactant). Close association between secretory cells of the mucosa and acid phosphatase is demonstrated by cytochemical method. It is suggested that secretory enzymes such as lysozyme and acid phosphatase may be either produced or transported by secretory cells of the middle ear mucosa. These enzyme secretions are considered a part of the enzymatic defense system of the middle ear.

Production of mucus in the middle ear and Eustachian tube. Embryology, anatomy, and pathology of the mucous glands and goblet cells in the Eustachian tube and middle ear

On the basis of quantitative studies of the mucus elements in 144 temporal bones and more than 5,000 biopsies the mucus producing capacity of the mucosa in the middle ear and Eustachian tube under normal conditions as well as in acute and chronic middle ear diseases is reviewed. In completely normal middle ears there was a very low goblet cell density and no mucous glands. Production of mucus does take place, but it is very slight. In acute conditions the goblet cell density in the Eustachian tube and middle ear increases, and metaplastic changes of the mucosa may occur, with formation of subepithelial and intraepithelial mucous glands. In chronic diseases, such as secretory otitis, there is a high gland and goblet cell density, which explains the increased production of mucus. In adhesive otitis the gland density is great, it is true, but most glands have become inactive and have degenerated. In chronic suppurative otitis, cholesteatoma, and sequelae to chronic otitis the goblet cell and gland density is moderately increased, but there are very marked individual variations which explain the great difference in the production of mucus. In active chronic diseases the mucus elements may increase enormously, and the mucus producing capacity of the epithelium may reach the heights of that of the respiratory mucosa.