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PubMed1998

Mesothelial cell proliferation in the scala tympani: a reaction to the rupture of the round window membrane.

The inner layer of the round window membrane is composed of mesothelial cells and this mesothelial cell layer extends to the scala tympani. This study describes the histopathologic findings of temporal bone analysis from a patient with bilateral perilymphatic fistula of the round window membrane. The left ear showed proliferation of mesothelial cells in the scala tympani of the basal turn adjoining the round window membrane. This cell proliferation is thought to be a reaction to the rupture of the round window membrane.

Cell Division↗
PubMed1984

Microscopic characteristics of round window problems in otology.

Round window membrane ruptures and perilymph leakage can present the complication or concomitant of sudden deafness and barotrauma. Pathological involvement of the round window membrane can occur in many otological diseases such as otosclerosis, otitis media, tumors, etc. Microscopic manipulations might result in an inadvertent round window membrane lesion and cochlear deafness. In recent years purposeful surgical lesions, including procedures for vertigo and cochlear implant surgery, are being made in the round window membrane. Examples of pathology involving the round window in human temporal bones are described. To understand better the clinical features of early round window rupture in humans,, controlled punctuate lesions were made in 36 chinchilla ears and studied sequentially. Round window membrane healing occurred as early as 3 days post-lesion, and was complete in all ears but 1 of the combined 7, 9 and 11-day group. Healing occurred primarily as a result of middle ear epithelial ingrowth and mesothelial cell reaction in the adjacent perilymphatic space of the scala tympani. These cellular events are described and discussed from an histological and clinical point of view.

Adult↗
PubMed1989

Ultrastructural studies of the human round window membrane.

An ultrastructural study of 14 round window membranes of seven human ears disclosed three basic layers: an outer epithelium lining the middle ear, a middle core of connective tissue, and an inner epithelium bordering the inner ear. Morphological evidence suggests that these layers participate in absorption and secretion of substances to and from the inner ear. A comparison of morphological features of round window membranes suggests that the average thickness of 70 microns does not change with advancing age. However, in the elderly, the connective tissue has a looser arrangement; there is an increase in ground substance; and elastic fibers thicken. Fibroblast nuclei become larger, rounder, and less uniform and have extensions. The ultrastructure of the "false round window membranes," with epithelial cells of the same type bounding both sides, suggests that these membranes consist of juxtaposed epithelial folds of the overlying promontory.

Aging↗
PubMed1987

Light and electron microscopic studies of a case with simultaneous Mondini and Michel deformities of the inner ears.

We performed light and electron microscopic studies on the temporal bones of a patient with genetic aplastic deafness, in which the right ear had a Mondini-type defect and the left ear a Michel-type anomaly. The round window of each ear was absent. The stapedial foot plate of the right ear was depressed at its central part and was covered by thin membrane. The course of the internal auditory meatus of the left ear was deviated ventrally. There was total aplasia of the cochlea in the left ear, while that of the right ear showed only three-quarters of a turn. In this ear, three sites of spherical bulging were found and were believed to represent outer hair cells. Other structures of the normal cochlear duct were not present. The modiolus of the left ear was round and dome-shaped, contained sparse nerve fibers and a primitive spiral ganglion. The saccule, utricle and semicircular canals of each ear were missing, so that a common cavity of the vestibular system was present. Several otoliths could be seen under the surface of the membrane covering the common cavity. No sensory cells or their related tissues could be found in either ear.

Aged↗
PubMed1989

[Influence of otitis media with effusion on perilymph and round window membrane].

To investigate the influence of middle ear effusion (MEE) on perilymph (PL) and the round window membrane (RWM), an experimental otitis media with effusion (OME) was manufactured in chinchillas by injecting the tympanic cavity with immune complexes. The presence of MEE lasted 9 days after the injection of immune complexes. Perilymph was aspirated on the fourth, tenth, 21st, and 60th days after the inoculation. The mean concentrations of albumin, IgG, histamine, and prostaglandin E2 (PGE2) were significantly greater in PL obtained from OME-induced ears than in those from normal control ears. The 3H-PGE2 placed on the RWM of pathologically affected ears passed into PL in significantly greater amounts, compared to normal control ears. The findings of the present study indicate that MEE affect the biochemical milieu of PL.

Animals↗
PubMed1993

The enlarged vestibular aqueduct syndrome (EVA syndrome).

The presentation to the Department of Pediatric Otolaryngology at the Children's Hospital of Michigan of a series of patients with sensorineural hearing loss and enlargement of the vestibular aqueduct prompted exploratory tympanotomy in three patients (two unilateral and one bilateral), for a total of four ears. These explorations were prompted by progression and/or fluctuation of hearing levels. The discovery of abnormal round windows in all four ears with a post-traumatic fistula present in one ear suggested the presence of a new association. A previously undescribed association of an enlarged vestibular aqueduct, sensorineural hearing loss and round window abnormality with potential fistula formation was identified. A review of the anatomy and physiology, literature review, and a prospective analysis with discussion of eight patients with enlarged vestibular aqueduct syndrome evaluated and treated at Children's Hospital of Michigan, is presented. We conclude that all children with sensorineural hearing loss should undergo extensive evaluation to determine etiology, including radiographic studies of the temporal bone. Further, the presence of an enlarged vestibular aqueduct should prompt the otolaryngologist to consider the presence of a round window abnormality and the potential for predisposition to perilymph fistula.

Child, Preschool↗
PubMed2001

Use of the malleus handle as a landmark for localizing the round window membrane.

Localization of the round window membrane is desirable in order to allow a more direct application of medication to the inner ear. A new procedure has been developed to deliver direct, near-continuous inner ear perfusion to the round window with the Silverstein MicroWick. In this office procedure, the wick is inserted through a tympanostomy tube into the round window niche. Accurate localization of the round window is a necessary component of this procedure. In an effort to ascertain the precise location of the round window, we examined 25 cadaveric human temporal bones and measured the distance from the umbo to the round window in each sample. We found that the round window was an average of 3.44 mm (+/- 0.68) from the umbo and was situated at an average angle of 113.2 degrees (+/- 9.8) from the long process of the malleus. Our simple and reliable determination of the relationship between the malleus handle and the round window niche allows for the accurate placement of the Silverstein MicroWick and other devices.

Cadaver↗
PubMed1993

[Etiology and fate of true perilymphatic fistulae].

Perilymphatic fistulas of the round or oval window in a traumatic context or following middle ear surgery or pathology, are reported. Rapid surgical exploration secures the best clinical results.

Diagnosis, Differential↗
PubMed2001

How do tympanic-membrane perforations affect human middle-ear sound transmission?

Although tympanic-membrane (TM) perforations are common sequelae of middle-ear disease, the hearing losses they cause have not been accurately determined, largely because additional pathological conditions occur in these ears. Our measurements of acoustic transmission before and after making controlled perforations in cadaver ears show that perforations cause frequency-dependent loss that: (1) is largest at low frequencies; (2) increases as perforation size increases; and (3) does not depend on perforation location. The dominant loss mechanism is the reduction in sound-pressure difference across the TM. Measurements of middle-ear air-space sound pressures show that transmission via direct acoustic stimulation of the oval and round windows is generally negligible. A quantitative model predicts the influence of middle-ear air-space volume on loss; with larger volumes, loss is smaller.

Ear, Middle↗
PubMed1998

[Study on the effects of hyaluronic acid-streptomycin perfusion through the round window on the function and morphology in guinea pig inner ears].

To investigate the effects of the hyaluronic acid-streptomycin (HA-SM) perfusion through round window on the function and morphology of the inner ear in guinea pig, membrous labyrinth mapping, temporal bone section after celloidin embedding, transmission electron microscopy, electrocochlegraphy (ECochG) and electronystagmography (ENG) were examined. The nystagmus duration induced by caloric test was obviously reduced in comparison with that of the preoperation (P< 0.01), while the action potential(AP) by ECochG was not obviously changed. The sensory cells of estibular organs were severely damaged, while the morphology of corti's organs were significantly damaged after HA-SM perfusion. The results suggest that the HA-SM perfusion through the round window may selectively destroy the vestibular function, whereas the auditory function is not obviously damaged.

Animals↗
PubMedDate not supplied

Thresholds of intracranially recorded auditory field potentials in the pigeon compared with compound action potential thresholds.

The compound action potential (CAP) thresholds provide a reliable indicator for cochlear functional integrity during experimentation in birds as well as in mammals. However, if experimental manipulations are necessary in the middle ear/inner ear spaces, the round window electrodes are often inconvenient. In search for an alternative for CAP recordings, intracranial recordings of acoustically evoked field potentials from the nucleus angularis/magnocellularis were made in pigeons using stereotactically placed electrodes. The responses were compared with those recorded from intracranial surface electrodes placed on the dura mater and compared with CAP responses recorded from the round window. The field potentials recorded from the nucleus angularis/magnocellularis contain a significant contribution from the auditory nerve, as large in amplitude as the CAP recorded at the round window. The recordings from the intracranial surface electrodes were noisier and the contribution from the auditory nerve was too small to be used as a fast monitor of the condition of the inner ear. Threshold curves as a function of frequency could be determined with an automated method from the nucleus angularis/magnocellularis with the same sensitivity and accuracy as from the round window CAP within a few minutes. These results demonstrate that stereotactic recordings of field potentials from the nucleus magnocellularis/angularis region are a suitable alternative to reliably monitor the condition of the inner ear when round window electrodes cannot be used.

Animals↗
PubMed1990

Electrophysiological effects of the clinically used local anesthetics lidocaine, lidocaine-prilocaine and phenol on the rat's inner ear.

Local anesthetics, even if applied to the outer ear canal, may still enter the middle ear, running the risk of penetrating the round window. To elucidate the effect of certain topical anesthetics on the inner ear, the round window niche in the laboratory rat's middle ear was exposed separately to lidocaine, lidocaine-prilocaine and phenol. Auditory brain-stem responses (ABR) were recorded at 2, 4, 6, 8, 12, 16, 20, and 31.5 kHz before the application, and 24 h, 3 weeks, 2 months and 6 months after exposure. After terminating the 6-month ABR measurements, the animal were sacrificed and the temporal bones fixed and decalcified for light microscopic analysis. All three drugs affected the ABR thresholds and the cochlear morphology with a pattern characteristic for each drug. At 24 h, all three substances caused severe impairment of ABR thresholds, followed by a period of restitution lasting up to 2 months. Even 6 months after exposure, the ABR thresholds at and above 12 kHz were impaired, as compared with the pretreatment level, for all substances tested. In the lower frequencies the original ABR threshold was reached in the order: (1) lidocaine, (2) lidocaine-prilocaine, (3) phenol. The cochlear structures were unaffected by lidocaine, whereas lidocaine-prilocaine and phenol caused morphological damage which was most pronounced after exposure to phenol. The heterogeneity of the changes in the ABR thresholds suggests differences in the mechanism of action of each type of local anesthetic investigated. The effects following lidocaine were transient. However, clinicians must be aware of the ototoxic potential of both lidocaine and phenol.

Anesthetics, Local↗
PubMed2004

The topographical anatomy of the round window and related structures for the purpose of cochlear implant surgery.

The treatment of total deafness using a cochlear implant has now become a routine medical procedure. The tendency to expand the audiological indications for cochlear stimulation and to preserve the remnants of hearing has brought new problems. The authors have studied the topographical anatomy of the internal structures of the ear in the area where cochleostomy is usually performed and an implant electrode inserted. Ten human temporal bones were obtained from cadavers and prepared in a formalin stain. After dissection of the bone in the area of round and oval windows, the following diameters were measured using a microscope with a scale: the transverse diameters of the cochlear and vestibular scalae at the level of the centre of the round window and 0.5 mm anteriorly to the round window, the distance between the windows and the distances from the end of the spiral lamina to the centre of the round window and to its anterior margin. The width of the cochlear scala at the level of the round window was 1.23 mm, and 0.5 mm anteriorly to the round window membrane it was 1.24 mm. The corresponding diameters for the vestibular scala are 1.34 and 1.27 mm. The distances from the end of the spiral lamina to the centre of the round window and to its anterior margin are 1.26 and 2.06 respectively. The authors noted that the two methods of electrode insertion show a difference of 2 mm in the length of the stimulated spiral lamina. The average total length of the unstimulated lamina is 2.06 and 4.06 in the two situations respectively.

Cochlear Implantation↗
PubMed1988

Anomaly of the round window a histopathological study using a graphic reconstruction method.

Although literature to date has reported that anomalies of the round window occur infrequently, no study to our knowledge has investigated such anomalies quantitatively. Thus, we developed a graphic reconstruction method and used it to study histology sections of the temporal bones. By this method we studied quantitatively the morphology of the round window of individuals with Mondini dysplasia of the inner ear and compared it to that of individuals with no anomaly. Iit was found that in 3 of 19 individuals with dysplasia, the total area of the round window was more than two standard deviations below the mean, thus small enough to be called anomalous. Moreover, the area of the round window was statistically significantly smaller in the ears from individuals with Mondini dysplasia, as a group, than in normal ears. This round window anomaly seems to be due to interruption of the normal development of the round window early in fetal life, as the result of poor development of the cartilage bar between the tympanic cavity and the subarachnoid space and also of the otic capsule in the hook portion of the basal turn of the cochlea.

Adolescent↗
PubMed1994

[Experimental perilymphatic fistula].

The round window membrane of the inner ear of 15 guinea pigs was removed under ketamine anaesthesia. Perilymph was aspirated through the round window in 8 guinea pigs. The round window membrane had regenerated spontaneously after 2 weeks. Light microscopy revealed hair cell loss localized to the apical and basal turns of the cochlea. Morphological examinations showed the most severe changes in these group of aspirated animals. Abrupt pressure imbalance may be a causative factor of sensorineural hearing loss.

Animals↗
PubMed1995

Heart beat modulation of spontaneous otoacoustic emissions in guinea pig.

It has been reported that background variation in the frequency of spontaneous otoacoustic emission (SOAEs) may arise from the cardiovascular system and that the side-bands in the spectra of SOAEs may be modulated by heartbeat. For better understanding of the mechanical influence of the cardiac cycle on cochlear functions under physiological and pathophysiological conditions, this study investigated heartbeat-induced modulation of SOAEs in guinea pig. Possible mechanisms of these phenomena are also discussed. The external ear canal acoustic signal, round window electric signal, and the ECG were recorded for off-line analysis from five pigmented guinea pigs with SOAEs. Time and frequency domain averages with synchronization of the heartbeat indicate that both the external ear canal acoustic and round window electric signal contain some component contributed by ECG and phonocardiography. High resolution FFT spectra suggest that SOAEs were modulated by heartbeat and respiration. Theoretically the change in the SOAEs could be from frequency modulation or a combination of frequency and amplitude modulations. Results of a heartbeat-synchronized average of a wave analyzer output at SOAE frequency indicates that amplitude modulation of SOAE does occur. Data obtained in the current experiment support the hypothesis that the heartbeat-related modulation of SOAE in guinea pig is a combination of frequency and amplitude modulation. The proposed mechanism is that pulsatile cochlear blood flow may cause oscillations in cochlear pressure and affect cochlear performance, resulting in heartbeat modulation of SOAEs.

Animals↗
PubMed1988

[Results and therapeutic indications of the electrical stimulation of the round window in 581 cases of bilateral total deafness].

Round Window Electric Stimulation necessitates to remove the ear drum to directly place the electrode tip in the round window niche. This test supplies the patient with a sound sensation in 93% of cases presenting a total deafness. It may be realized either under local or general anesthesia owing to brain stem evoked auditory responses. This test supplies the surgeon with precious informations regarding the cochlear implant indications.

Cochlea↗
PubMed1999

Regulation of inner ear fluid in the guinea pig cochlea after the application of saturated NaCl solution to the round window membrane.

The regulation of K+ and Na+ in the inner ear fluid of the guinea pig was studied after the application of saturated NaCl solution to the round window membrane. K+ and Na+ activities in the scala tympani increased rapidly and then decreased. K+ activity in the scala media increased immediately, but Na+ activity continued to increase during the period of observation. K+ activity in the scala vestibuli continued to increase in the observation period. Na+ activity in the scala vestibuli increased and then decreased. The endocochlear potential decreased immediately to approximately 20% of its initial level. Total activities of K+ and Na+ increased immediately and then decreased in both the scala tympani and scala media. The total activity of K+ and Na+ increased slowly and showed no regulatory decrease in the scala vestibuli. Thus, changing patterns in the total activity of K+ and Na+ were similar for the scala tympani and scala media, but not for the scala media and the scala vestibuli. Different patterns of K+ and Na+ activities among the three scalae indicate that their mechanisms for regulating inner ear fluid differ.

Animals↗