Eardrum

EARDRUM (membrana tympani), represents a membrane that separates the outer ear canal from the middle ear. The eardrum is attached by its thickened edge to the bone (sulcus tympanicus) with the help of a fibrous ring (annulus tympanicus). In the area of the incisura Rivini, this ring is absent and the eardrum comes into direct contact with the skin of the ear canal here. The eardrum has an elliptical or oval shape. The long diameter of the membrane is 9-10 mm, the transverse diameter is 8-9 mm. In relation to the bone of the ear canal, the eardrum is inclined from back to front and from top to bottom. The angle formed by the eardrum with the posterosuperior wall of the ear canal is usually about 140°; with the anteroinferior wall of the ear canal, the eardrum forms an acute angle of about 27° (see figure - Middle Ear). It should also be noted that the central part of the eardrum is depressed inward and that the inner segment of the bony ear gradually descends downward, so that a bay-like depression is formed at the lower edge of the membrane. In the embryo, the eardrum is positioned more horizontally than in adults: in newborns, the position of the eardrum differs little from its position in adults, but the inclination is somewhat greater. Embryology. The embryonic rudiment of the eardrum is located in the area of the dorsal end of the first oral fissure; this end lies under the epidermis of the lateral surface of the face until the end of the 7th week. At first, only the anterior half of the eardrum is formed as a membrane; the posterior half develops in connection with the expansion of the tympanic cavity in the dorsal direction. At the beginning of the 4th month, the eardrum has a continuous layer of mesodermal tissue. According to Krause, the embryonic eardrum already has an inclined position. It is covered on the outside by a two-layer epidermis, on the inside by the flat epithelium of the tympanic cavity, and between these two layers there is mesodermal tissue. From this mesodermal tissue, the membrana propria subsequently develops. After birth, the desquamation of the superficial layer of the eardrum occurs, which can continue for up to two months and ends with the formation of a shiny epidermis. Comparative anatomy. Among amphibians, the eardrum is found in frogs; in snakes (reptiles) there is no eardrum. It is present in turtles, in some species of lizards, in crocodiles, in birds, and in mammals. History. Hippocrates was the first to mention the eardrum and compared it to a thin spider web. In Aristotle, the eardrum in animals is apparently mentioned. In the subsequent period of anatomical history, the anatomy of the ear made little progress: Copho junior (end of the 11th century) and Mondino (1275-1326) mention the eardrum very vaguely. In the writings of Alessandro Achillini of Bologna (1463-1512) under the title "Annotations anatomicae in Mundinum" there are mentions of the eardrum, the malleus, and the incus. A number of 16th-century anatomists (Vesalius, Falloppio, Ingrasio, Eustachio) already give more detailed anatomical descriptions. Morphology. The eardrum is a membrane with an average thickness of 0.1 mm. From the inside, the malleus is connected to the eardrum, the handle of which is pulled inward by the tensor tympani muscle, which is why, mainly, the funnel-shaped depression of the eardrum in the center is created; at the same time, the short process of the malleus moves outward, forming in front of and behind it the anterior and posterior horizontal folds of the membrane. The eardrum is divided according to its structure into two parts: the lower part, located below the short process and the folds of the membrane, and the upper part, above them. The lower segment, being larger, is called pars tensa, and the upper one-pars flaccida or membrana Shrapnelli (see figure on p. 786). Pars tensa consists of three layers: on the outside there is the epidermis (stratum cutaneum), in the middle the fibrous layer (stratum fibrosum), and on the inside the mucous membrane (stratum mucosum). The epidermis consists of several layers of flat epithelial cells; the upper layer is keratinized. Up to the second year of life, and in pathological hyperplastic changes associated with otitis and at a later age, a series of cubic cells adjoin the thickened subepidermal layer, then layers of flattening cells, and finally, on top, a thick keratinized layer (Wittmaack). The middle fibrous layer of the eardrum consists of external radial fibers and internal circular ones. Radial fibers are present in the eardrum everywhere, except in the membranae Shrapnelli, and diverge from the depressed center-umbo to the periphery, forming a denser and thicker network of fibers around the handle of the malleus. Inside the radial fibers are the circular ones, which intersect the former at right angles. In contrast to the radial fibers, they are arranged in a denser network at the periphery and are almost completely absent in the area of the umbo. The tension of the circular fibers plays a role, together with the above-mentioned cause of the handle of the malleus being pulled by the tensor tympani muscle, in the funnel-shaped depression of the eardrum in the center. In all layers of the eardrum there are elastic fibers: the annulus fibrosus represents a significant thickening, mainly of radial fibers, among which there are bundles of circular ones. The connection of the eardrum with the periosteum of the handle of the malleus is also carried out, mainly, by radial fibers. The layer of mucous membrane located on the inside of the eardrum consists of flat endothelium-like cells; the latter, in a completely normal mucous membrane of the middle ear, are located without a clear submucosa on the stratum fibrosum. Blood vessels and nerves. The blood vessels of the eardrum come from both the outer and middle ear. The outer network is formed by a branch of the art. auricularis profunda, which runs along the handle of the malleus. The inner network comes from the vessels of the middle ear, namely, the art. stylomastoideae and art. tympanicae. The arterial branches pass into the venous plexuses. The inner and outer venous networks are connected to each other with the help of perforating veins at the handle of the malleus, at the edge of the eardrum, and in the intermediate zone. The lymph vessels of the membrane form an inner network under the epithelium and an outer one under the epidermis, which anastomose with each other. The nerves of the eardrum, which according to Arnold originate from the n. temporalis superficialis, pass from the posterosuperior wall of the ear canal, behind the handle of the malleus, onto the eardrum, where they run along it with several small branches and form nerve plexuses in the epidermis and mucous membrane. Biophysical and biochemical properties. The peculiarities of the morphology of the eardrum are of great importance in its physiology. On the basis of experimental data, Helmholtz came to the conclusion that the shape of the eardrum contributes to its strong resonance (flat membranes give incomparably less resonance). On the other hand, the shape of the eardrum plays the following role: strong air vibrations cause significant movements of the membrane, similar to the action on the long end of a lever. At the same time, relatively very small excursions of the end of the handle of the malleus occur, similar to the action on the short end of a lever. According to Helmholtz, the amplitude of vibrations of the central part of the eardrum is approximately 4 times greater than the excursions of the end of the handle of the malleus. Thus, the amplitude of vibrations is sharply reduced when transmitted to the chain of auditory ossicles and at the same time increases in strength. The richness of the eardrum in elastic fibers allows it, in case of a change in position under the influence of air pressure fluctuations, to quickly return to its original position. The eardrum has greater resistance in childhood. When studying the effect of increased air pressure, one should distinguish between a sudden increase and a gradual one, with respect to which the eardrum is more resistant. With a gradual increase in atmospheric pressure, a normal eardrum withstands pressure in 77% of cases--up to two atmospheres, in 66%-up to 1-2 atmospheres, in 11% - less than 1 atmosphere. The eardrum is under the influence of a certain tension of its elastic fibers, as well as the mechanism of the ossicles, in a state of certain tone. Under normal conditions of the latter, the respiratory fluctuations of the eardrum occur within very small limits--according to M. F. Tsitovich, from ¹/₃ to 1 mm of a manometer and occur either outward or inward. V. I. Voyachek established the size of these fluctuations on photomanometric photographs at about V/₂ mm of an alcohol manometer. M. F. Tsitovich pointed out that the absence of respiratory fluctuations of the eardrum is usually associated with a violation of the auditory function. The movement of the eardrum outward is associated with an increase in pressure in the middle ear, which occurs when the Eustachian tube is closed during inhalation; when the air in the middle ear is rarefied due to the opening of the Eustachian tube during exhalation, the eardrum is drawn inward. With the help of a manometer, pulsating fluctuations of the eardrum were also established. When transmitting sound waves, the eardrum, as a membrane with a small mass in relation to its surface, not only resonates to tones similar to the natural tones of the membrane, but also to tones that differ significantly in height. The connection of the eardrum with the chain of ossicles and (through the latter) with the fluid of the labyrinth ensures a certain uniformity in the perception of tones of different heights. (Seebek, cited by Schaffer, Giesswein). Movements of the eardrum have been observed by various authors. Berthold studied the movement of the membrane optically.

The membrane was set into vibration by means of tuning forks (see.), mounted on bone, and with the help of a rotating König mirror, the vibration of the flame was studied, with the auditory canal being used for gas. Low tones produced wavy lines, the elevations of which were farther apart than with high tones. The height of elevation and depth of depression with high tones were more pronounced than with low tones; Nagel and Samoylov conducted similar research. Mach and Kessel (cit. Politzer) studied the movements of the membrane in a dead ear with the help of a special stroboscope. Wada (cit. Schaffer) when studying on various animals investigated the vibrations of the eardrum at various tones, with the greatest vibrations being caused by the tones a^s-a*. In experiments on pigeons, it was found that different parts of the eardrum vibrate differently at the same tone. After the death of the animals, as well as after deep anesthesia and destruction of the musculus, tensor tympani, vibrations of the eardrum were no longer observed for all tones, but only up to a certain limit, which the author explains by the loss of the membrane's normal tone. Of other physiological moments, the sensitivity of the eardrum is of interest. According to the research of Manasse, tests for thermal irritation on a normal membrane gave the following results: heat was not felt, but cold was perceived, and in some individuals, cold thermal irritations were felt as warm. With mechanical irritation by hairs, touching was perceived as a tone or crackle, and with increased pressure, pain appeared. As for the biochemical properties of the eardrum, according to Urbantschitsch, H₂S penetrated through the eardrum in 8-5 minutes, and carmine (Schonemann and Steinschneider) in the course of several hours completely saturated the eardrum and was found in the middle ear. Methods for studying the eardrum: otoscopy (see.), Hegener's method of photographing the eardrum and the method of observing it in Luscher's ear microscope. When studying the otoscopic picture, first of all, attention is paid to the color of the eardrum (see table, fig. 1), which is usually pearly-gray or gray and consists of the color of the beam of rays directed by the researcher onto the eardrum, the membrane's own color, and the color of the surface visible through the eardrum. In places where light cannot penetrate through the eardrum due to the thickness and density of the fibers in that place, a white tint of the eardrum is visible. This color is found around the umbo. The thicker the eardrum, the clearer its own ashen color; with age it becomes whitish. The anterior segments of the eardrum appear darker, since the distance from them to the eye is greater than from the posterior part. The more transparent the eardrum, the more light passes through it inward, and the darker it appears. Under the influence of various pathological processes in the middle ear, the color of the eardrum can change. During otoscopy, first of all, an orienting point on the eardrum is found, namely the short process of the malleus, processus brevis. It appears as a whitish-yellow point the size of a pinhead, rising on the surface of the eardrum, not far from its upper edge, closer to the front. Downward from the short process goes the handle of the malleus, visible through the eardrum as a whitish stripe of varying thickness, ending in an expansion near the middle of the eardrum. Anteriorly and posteriorly from the short process, the so-called folds of the eardrum (anterior and posterior) extend. With good transparency of the membrane, posterior to the handle of the malleus, parallel to it, the light contour of the long process of the incus is visible; at the lower end of the long process there is a joint between the incus and the stapes. At the lower end of the incus, a light strip extending posteriorly and upward—the tendon of the stapedius muscle—is sometimes visible. In the upper-posterior part of the eardrum, a grayish-white strip running from front to back and upward—the chorda tympani—is sometimes visible. In this same segment of the eardrum, a more densely outlined triangular area is visible, because here there is a doubling of the mucous membrane on the posterior side, the so-called Troeltsch's pocket. Sometimes the entrance to the niche of the round window is projected onto the eardrum as a dark shadow in its lower-anterior part. With a high position of the bulbus of the jugular vein and dehiscences of the bony wall surrounding the vein, a bluish translucence (venous blood) is visible in the lower part of the eardrum. The latter, due to the epidermis having a fatty surface, has a shine. Provided the light ray falls perpendicularly to the surface of the eardrum, a reflection of the rays is obtained, the so-called light reflex, going from the umbo obliquely downward and having a triangular shape. Small reflexes are also obtained: 1) on the short process, 2) in the middle of Shrapnell's membrane, and 3) at the very edge of the lower-anterior segment of the eardrum, at the border with the lower wall of the auditory canal. Since the light reflex is not organically connected with the eardrum, as its position changes under the influence of various pathological factors, the light reflex also changes its shape or may disappear altogether. For localization purposes, the eardrum is conventionally divided into four segments (quadrants): one diameter is drawn through the handle of the malleus mentally further down to the edge of the membrane, the second diameter perpendicularly to the first—through the umbo (see figure on p. 786). Four quadrants of the eardrum are obtained: upper-anterior, lower-anterior, upper-posterior, lower-posterior. Pathological changes of the eardrum. The normal position of the eardrum is determined by the equality of atmospheric pressure on the outer side of the membrane with the pressure that exists in the middle ear. The normal pressure in the middle ear depends on the proper ventilation of the Eustachian tube. If this ventilation is disrupted under the influence of various pathological causes, then due to the absorption of air, the pressure in the middle ear decreases and an excess of external pressure over internal pressure occurs. As a result of this, the eardrum is retracted inward. The objective picture of a retracted eardrum (see table, fig. 2): the handle of the malleus lies more horizontally and is perspectively shortened; the short process, on the contrary, is retracted into the membrane and protrudes outward; at the same time, the anterior and posterior folds of the membrane, especially the latter, protrude more clearly than in the norm. Membrana Shrapnelli is retracted inward, so that here the neck of the malleus is often visible; as for the triangular light reflex, with retraction of the membrane, depending on the degree of retraction, it either decreases, losing its correct shape, or disappears altogether. If the disruption of ventilation in the middle ear lasts for a long time, then hydrops ex vacuo occurs in the tympanic cavity; the transudate fluid of the middle ear can give a yellowish-green tint to the color of the membrane; in some cases, it is possible to see the line of transudate, i.e., the level of fluid in the middle ear, in the form of a dark line, concavely running across the eardrum. With head movements, the transudate line changes, and sometimes air bubbles are also visible. In otosclerosis, the hyperemic inner wall of the middle ear can give the eardrum a reddish tint in the area of the upper-posterior quadrant. Inflammatory changes of the membrane can develop from the side of the external auditory canal as well as from the side of the middle ear. From the otoscopic picture, it is not always possible to determine whether we are dealing with a disease of only the eardrum or if the lesion of the latter is a consequence of a process in the middle ear. Acute inflammatory changes of the eardrum are manifested in the injection of vessels running along the handle of the malleus (see table, fig. 6). Soon it is joined by the injection of the peripheral vascular network; further, the redness captures the entire eardrum, starting from the upper-posterior quadrant and Shrapnell's membrane (see table, fig. 7). The short process is visible for a long time, but, in the end, it also disappears. After the hyperemia comes the serous impregnation of the eardrum and its round-cell infiltration. During otoscopy, it is difficult to demarcate the eardrum from the external canal, due to the transition of inflammation to the latter (see table, fig. 8). In some forms of otitis (influenza), bubbles of various sizes can form on the eardrum, filled with blood or serous fluid. These bubbles can burst and then a gray deposit of detached epithelium appears on the eardrum or in the depth of the auditory canal. If one has to deal not only with a disease of the eardrum but also with inflammation of the middle ear, as is often the case, then exudate accumulates in the middle ear, which gradually produces pressure on the eardrum, and the latter bulges outward. If the exudate has accumulated in the middle ear quickly, and the middle and outer layers of the membrane have undergone little inflammation, a translucence of the exudate through the healthy layers is obtained, and the membrane has a shiny metallic tint. The bulging most often occurs in the area of the upper-posterior quadrant of the eardrum, which can sometimes overhang the lower part of the membrane like a papilla. If the process has reached a noticeable bulging of the eardrum, then usually the exudate ruptures through the latter and 1. л I'Л 1, Л II ИЛИ II K 1-КПП II K л an opening is formed in the eardrum, the so-called perforation (see table, fig. 4 and 5).

If the process in the middle ear has not gone too far, the disease can be eliminated without perforation. - As the inflammation subsides, the redness of the eardrum gradually disappears. When the inflammatory phenomena pass, the eardrum appears gray and somewhat opaque. The injection of blood vessels in the eardrum along the handle of the malleus persists for a long time. With complete elimination of the process, the eardrum may either completely regain the appearance it had before the disease, or if new connective tissue has formed in the stratum cutaneum or mucosum, then the eardrum either remains grayish cloudy or, due to the deposition of lime crystals, clearly demarcated white spots appear (see table, fig. 3).-Perforations that occur during acute inflammations may either heal or become chronic. Only the outer and inner layers of the eardrum participate in the formation of the scar, as a result of which the scar is thinner and more transparent than the rest of the eardrum. Atrophies of the eardrum, which are also more transparent and appear darker compared to the rest of the eardrum, resemble scars. The atrophic part of the eardrum cannot resist air pressure to the same extent as the unchanged part and is usually retracted inward. Atrophies can be distinguished from scars by their larger size and better demarcation. Both scars and atrophies show greater mobility compared to the healthy part of the eardrum during the Siegle's pneumatic funnel test (see below). According to the theory of Wittmaack, hidden infantile otitis of early childhood also affects the appearance of the eardrum (atrophies, retractions, opacities), and also influences the character of the development of the pneumatization of the mastoid process. Thus, according to Wittmaack, the appearance of the eardrum often allows one to draw conclusions about the nature of the pneumatization of the mastoid process. Talpis and Lieberman studied the relationship between the appearance of the eardrum and the structure of the mastoid process and established a certain correlation between them. In chronic perforations of the eardrum, they should be distinguished by location: 1) central, 2) marginal, and 3) perforations of Shrapnell's membrane. The location of the perforation plays a significant role in the diagnosis of chronic purulent lesions of the middle ear and their prognosis (see Middle ear). Large perforations are easily noticeable by their clear edges, which demarcate the defect from healthy tissue. The edges of small perforations are indistinct, and their diagnosis is more difficult; sometimes even large perforations present difficulties when the mucous membrane of the middle ear is inflamed, reddened, thickened, and merges with the reddened eardrum. In such cases, one should look for any remnants of the eardrum or ossicles, or resort to probing. In unclear cases, one sometimes has to wait for the weakening of inflammatory phenomena. Small pieces of wax, dried secretion, or blood on the eardrum can in doubtful cases be confused with small perforations by an inexperienced eye. Sometimes with inflammatory changes in the middle ear, the inflammatory secretory fluid pulsates, exiting through a small perforation. The reflection of light on the pulsating droplet of discharge gives the so-called pulsating reflex. In a completed or subsiding process in the middle ear, one can also see the so-called dry perforations. In difficult diagnostic cases, it is necessary to resort to the following methods: 1. Application of a magnifying glass, which is held in front of the ear canal. For this purpose, an ordinary magnifying glass of about 13 diopters or a specially constructed Brunings magnifying glass can be used. 2. Probing. For this, a thin probe, preferably silver or nickel silver, with a button on the end, is used with caution. 3. Application of Siegle's pneumatic funnel. The latter is closed with glass on the outside and on the side wall has a small branching tube for connecting with a rubber tube and a small balloon. With its help, one can alternately compress and rarefy the air in the auditory canal. A normal eardrum during the funnel test shows mobility: the greatest movement occurs in the area of the upper-posterior quadrant of the eardrum and membranae Shrapnellii. The light reflex on the right eardrum shortens and the eardrum from the outside: 1-long process of the incus; 2-plica malleolaris posterior; 3-short process of the malleus (processus lateralis); 4-pars flaccida membranae tympani (strengthened at the edge of the incisurae Rivinii); 5-handle of the malleus; 6-umbo membranae tympani. The mobility of the atrophic areas of the eardrum is significantly reduced

corning'). or completely destroyed in the presence of the so-called adhesive process in the middle ear, when scars form between the eardrum and the walls of the middle ear. In the presence of perforation, the test with a pneumatic funnel gives no results. The diagnosis of perforation is established by the following method: insufflation is performed through the Eustachian tube using Politzer's balloon with or without a nasal catheter, and at the same time the patient's ear is connected to the examiner's ear with a rubber tube (otoscope); in the presence of perforation, a clear whistling sound of air passing through the perforation opening is heard. For the diagnosis of perforation, the so-called Valsalva maneuver is also used. If the patient is made to puff out his cheeks with the mouth closed and nose pinched, then even with a small perforation, a whistling sound of air passing through the opening will be clearly heard. However, this maneuver gives no results when the Eustachian tube is blocked. Primary diseases of the eardrum. Diseases of the eardrum itself, in which it is primarily affected, occur comparatively rarely. - Acute myringitis (myringitis acuta) in most cases accompanies a general diffuse disease of the external auditory canal, but can also occur separately. Subjective symptoms are usually weakly expressed, but in hemorrhagic inflammation, for example, in influenza, severe boring pains in the ear and noise occur. The eardrum is hyperemic to varying degrees, covered with ecchymoses or small vesicles containing serous or purulent fluid. Unlike diseases of the middle ear, hearing is unchanged or slightly changed, which is characteristic of myringitis. In the acute inflammatory stage, compresses are applied to reduce pain. If the vesicles on the eardrum are considerable in size, they are punctured with a paracentesis needle, and then the macerated eardrum is lightly dusted with Ac. boricum pulveratum subtillissimum from a powder blower. Within a few days, the process usually resolves. -- Chronic myringitis (myringitis chronica) is usually only part of a general disease of the external auditory canal, or it can develop from a prolonged acute myringitis. The eardrum is macerated, sharply reddened in those areas where it is devoid of epithelium. Sometimes there are small granulations. In chronic myringitis, as in acute, unlike processes in the middle ear, hearing is not impaired. If granulations are present on the eardrum, it is necessary to differentiate them from a small perforation of the eardrum, the edges of which are surrounded by granulations. For diagnosis, insufflation is used. - Treatment. Individual granulations are cut off with Hartmann's ear forceps after preliminary anesthesia with a 10% cocaine solution; in the presence of maceration, the eardrum is cauterized with a 5-10% solution of Arg. nitrici, also after anesthesia, and then boron powder is insufflated. -- Changes in the eardrum associated with professional hazards. In the metal industry, metal particles can cause damage to the eardrum. In the chemical industry, burns of the eardrum are observed. Work in caissons, associated with a violation of normal air pressure, causes significant injection of the eardrum, and sometimes blood extravasates; atrophic eardrums can even rupture. -- Traumas to the eardrum can be divided into three groups: 1) those arising from direct mechanical impact; 2) associated with sharp fluctuations in air pressure; 3) associated with fractures of the middle ear. In direct trauma to the eardrum, there is usually an irregularly shaped perforation with uneven edges, depending on the size and shape of the injuring object; around the perforation there are blood clots. Bleeding in trauma is usually insignificant. Traumas to the eardrum are usually accompanied subjectively by a crackling sound, pain, dizziness, decreased hearing, and tinnitus. If the wound does not become infected and is not complicated by inflammation of the middle ear, the eardrum heals quickly. Atrophic eardrums heal slowly. Indirect traumas to the eardrum are more common than direct ones. An example of such traumas are ruptures of projectiles, a blow to the ear, too vigorous nose blowing or insufflation, especially in the presence of scars on the eardrum, etc. Subjective symptoms are the same as in direct traumas. Ruptures of the eardrum most often occur in the anterior-inferior quadrant, have uneven edges covered with hemorrhages. Special treatment, such as washing, wiping, insufflation, is contraindicated in all types of trauma; preventive insertion of cotton wool into the external auditory canal is recommended. Damage to the eardrum may be associated with fractures of the middle ear in trauma to the base of the skull (see Middle ear). If in such cases the damage does not extend to the eardrum, but there is hemorrhage in the middle ear (haematotympanum), then the eardrum takes on a reddish tint due to the transparency of the blood. Among the rare diseases of the eardrum are noted: herpes, associated with a similar disease of the face and pharynx. No special treatment is required. Naevus cutaneus has been observed as a continuation of a similar disease of the auditory canal. Kohrer observed varices in the form of a highly protruding, blood-colored vesicle with tiny vessels on the eardrum. Myringitis tuberculosa-tbc of the eardrum is usually observed in the form of an infiltrate (exclusively rarely a tubercle), which upon disintegration forms multiple perforations of the eardrum (see Middle ear). Myringitis villosa is a very rare disease; with almost complete destruction of the stratum proprium of the eardrum, there is connective tissue thickening and clouding of the eardrum and papillary growth on the outer surface. - Cholesteatoma of the eardrum occurs in the form of brilliantly white, pinhead-sized or slightly larger grains, which are located on the eardrum and histologically consist of flat epithelium arranged in the form of bulbs; contains cholesterol crystals (epithelioid cholesteatoma). Endothelioid cholesteatoma originates from the stratum cutaneum and is enclosed in a connective tissue capsule lined with cylindrical epithelium and containing hematoidin. - Artificial eardrums (see Middle ear). The use of artificial eardrums is indicated only when there is severe bilateral deafness, less than half a meter for whispered speech. They can be used for large and small defects of the pars tensa of the eardrum, especially the posterior quadrants, but only in the absence of purulent discharge. Usually, a small cotton ball soaked in boron glycerin is used as an artificial eardrum. Commercial eardrums made of different materials are less convenient.