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PubMedDate not supplied

Mucopolysaccharidosis I-H (Hurler's syndrome) and human temporal bone histopathology.

Six temporal bones from three patients with mucopolysaccharidosis I-H are described. All three patients were diagnosed as having mucopolysaccharidosis I-H by enzyme analysis, and all fit the phenotypic criteria of this disease. Family histories of the three cases described were negative for mucopolysaccharide-storage diseases. All three of the patients suffered chronic recurrent otitis media from infancy through death. Common histopathologic findings include otitis media, residual mesenchyme in the round window niche, partial occlusion of the middle ear cavity, and basophilic concretions within the stria vascularis. The common severe histopathologic changes observed in this study and similar findings in the temporal bones described in other studies lead the authors to believe that ear involvement in this disease may be more common than was previously suspected.

Child↗
PubMed1987

Glycerol-induced changes in the cochlear responses of the guinea pig hydropic ear.

Pigmented guinea pigs were chronically implanted with bilateral round-window electrodes. Endolymphatic hydrops was induced by obstruction of the endolymphatic duct on one side. At 1-5 months post-surgery, glycerol was orally administered to each animal and the acute effect on cochlear and eighth nerve responses was investigated. Doses from half to four times the clinical dose of glycerol failed to improve the CAP audiogram in operated ears and were often found to raise the thresholds. Glycerol was found to diminish the amplitude of the summating potential as well as that of the compound action potential. Similar effects were observed for the higher doses in the control ears, although no effect was seen when doses used were equal to or less than the clinical dose. Our data suggest that the cochlear conditions in the guinea pig model of hydrops differ notably from those seen in patients with Ménière's disease.

Animals↗
PubMed1992

Influence of middle ear immune response on the immunological state and function of the inner ear.

According to clinical experience, a causative correlation between otitis media and sensorineural hearing loss is likely. During an otitis media, inflammatory mediators should be released and diffuse through the round window membrane to cause an immune response of the inner ear. Using 20 guinea pigs, an immunologically caused otitis media was induced. Auditory evoked potentials were registered by means of electrocochleography and electric response audiometry from day 0 to day 7. Each time, before and after starting the immune response serum, middle ear effusion and perilymph were sampled and the concentration of interleukin-2 (IL-2) analyzed. Decalcified temporal bones were examined immunohistochemically. In this study, IL-2 was found in the middle ear effusion and perilymph, and there was evidence of an immune response of the inner ear during an otitis media. Histological results were in close correlation with this event. Electrophysiological data showed conduction deafness and signs of sensorineural hearing loss with a maximum at day 3.

Animals↗
PubMed1999

Combined rupture of Reissner's membrane and round window: an experimental study in guinea pigs: experimental double-membrane rupture.

OBJECTIVE: Hearing loss caused by combined rupture of Reissner's membrane and the round window (RW) membrane (the double-membrane rupture) may differ depending on the site of the lesion on Reissner's membrane. The purpose of this experimental study was to reveal the relationship between the hearing impairment and the site of the lesion on Reissner's membrane. BACKGROUND: According to experimental studies on perilymphatic fistula (PLF), profound hearing loss is not induced by rupture of RW alone, but by the double-membrane rupture. However, the mechanism responsible for hearing loss in the double-membrane rupture remains unclear. METHODS: Compound action potentials (CAPs) of the cochlear nerve in response to tone pip stimuli (1, 2, 4, and 8 kHz) were recorded before the lesion, 90 minutes after the Reissner's membrane rupture, and 90 minutes after subsequent laceration of the RW. Reissner's membrane was ruptured at one of the four turns for comparison. RESULTS: The double-membrane rupture caused a more severe increase in CAP thresholds than seen with separate ruptures, when the Reissner's membrane was ruptured at the second turn. Such pronounced increase in threshold was not seen in ears with the rupture at other turns. CONCLUSIONS: The double-membrane rupture causes varying degrees of hearing loss depending on the site of the lesion of Reissner's membrane. When the Reissner's membrane was ruptured at the second turn, the most severe hearing loss was detected.

Animals↗
PubMed1994

The cochlear blood flow: a comparison between the laser Doppler and the microsphere surface methods.

Since the introduction in the early 1980s, of the laser Doppler (LD) method for measuring cochlear blood flow (CBF) it has been debated whether the measured changes reflect the total or regional blood flow and whether the method per se influences the CBF. In order to answer those questions, the effect of one vasodilating drug, sodium nitroprusside, was investigated after topical application on the round window membrane (RWM) with respect to its influence on CBF. Two different techniques, the microspheres surface method and the LD method, were used. Untreated animals and animals which received saline or nicotine acid on the RWM were used as controls. The effects on CBF and blood pressure (BP) were continuously registered with LD. When a maximal flow had stabilized, 6 x 10(6) microspheres were injected into the left side of the heart. After the microspheres had been distributed within the body, the animals were killed. Both cochleae were microdissected and the microspheres counted turn by turn in the lateral wall. The number of spheres in the two ears was compared and the difference was recorded as the increase caused by the drug. The percentage change in CBF measured using the LD was compared with that obtained by using the microsphere surface method (MSM). No change in CBF measured by the two techniques was registered in the untreated animals, or after saline or nicotinic acid, while sodium nitroprusside induced a substantial increase in CBF. The mean percentage change of CBF measured with the LD method was compared with the calculated mean percentage change of microspheres for all turns in the cochlea, and in the first turn. Student's t-test and the linear correlation coefficient were calculated.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Topical↗
PubMed1990

Impulse patterns of auditory nerve fibres to extra- and intracochlear electrical stimulation.

The impulse patterns of single auditory nerve fibres in cats with normal hearing and in deafened cats were studied during electrical stimulation of the cochlea at different locations. In the case of extracochlear round-window membrane stimulation, cats with normal hearing showed lowest thresholds (32 dB re 1 microA rms) for sinusoidal stimulation in the frequency range 50-300 Hz. These thresholds were independent of the acoustically determined characteristic frequencies of the fibres. The fibres of acutely deafened cats (by Neomycin) showed no spontaneous activity and could be activated only electrically with similar current values as in normal hearing cats. The action potentials were highly synchronized with the electrical signal up to 12.8 kHz. Intracochlear electrical stimulation was performed using a human multichannel cochlear implant electrode array. The excitation thresholds of the fibres for current stimulation showed poor place dependency when using different electrodes (monopolar) in the first turn of the cochlea with a remote indifferent electrode inside the middle ear. Better localization could be obtained when using bipolar stimulation with electrode pairs (electrode distance 0.75 mm) in the scala tympani. With parallel bipolar stimulation at two different locations (distance 1.5 mm) using two independent current sources a clear interaction could be observed in the firing pattern of single fibres. The measured gain and phase relations between current signal and neuronal response allowed the calculation of a model describing the summation of current density vectors acting on an excitable nerve membrane model. On the basis of these measurements, input networks were calculated to improve the channel separation of multichannel cochlear implants.

Action Potentials↗
PubMedDate not supplied

The preparation of acetic acid for use in otic drops and its effect on endocochlear potential and pH in inner ear fluid.

The ototoxicity of an otic drop preparation containing 2% acetic acid and 3% propylene glycol (VoSol, Denver Chemical Co., Humacao, PR) was investigated according to measurements of endocochlear potential (EP) and inner ear fluid pH. The application of this preparation to the round window membrane for 30 minutes caused a depression in EP from 80.5 +/- 2.5 mV (mean +/- SD; n = 6) to 11.7 +/- 7.7 mV, and lowered inner ear fluid pH from 7.55 +/- 0.09 to 5.06 +/- 0.19 (n = 6) in perilymph and from 7.52 +/- 0.07 to 5.88 +/- 0.63 (n = 6) in endolymph. Two percent acetic acid produced similar changes after 30 minutes: EP was reduced from 83.0 +/- 2.2 mV to 34.0 +/- 2.9 mV and endolymphatic pH from 7.49 +/- 0.04 to 6.83 +/- 0.21 (n = 4). However, the application of artificial perilymph of pH 4 titrated with HCl induced no significant changes in either EP or endolymphatic pH. We suggest that the mechanisms of ototoxicity in the otic drop preparation are Na+ and K+-ATPase inhibition, and that such inhibition is due to the intracellular acidification of strial cells resulting from the penetration of acetic acid across the cell membrane, and to the direct and synergistic actions of propylene glycol.

Acetates↗
PubMed1999

Intratympanic therapy for Ménière's disease. High-concentration gentamicin with round-window protection.

Many therapeutic options exist for the management of patients with Ménière's disease. In the last few years, the use of intratympanic gentamicin has been investigated as an alternative treatment to vestibular nerve section or labyrinthectomy. In humans, the concentration of gentamicin used for intratympanic treatment of vertigo ranges from 10 mg/mL to 40 mg/mL, and the number of doses from 2 to 14, with a total administered amount between 6 and 2.400 mg. Here lower doses of gentamicin were used, usually had the lowest incidence of hearing loss, but more injections were needed to ablate vestibular function. The purpose of this study was to evaluate the acute and chronic ototoxic effects of intratympanic high-concentration gentamicin after having obliterated the round-window niche with connective tissue in 11 subjects' ears with Ménière's disease. Intratympanic gentamicin was administered according to a predetermined and fixed schedule consisting of two doses of 0.5 mL gentamicin solution, injected once a week with a drug concentration of 80 mg/mL. The total dose of gentamicin was < or = 80 mg. The charts of the patients were surveyed in accordance with the 1995 AAO-HNS guidelines. Three patients had recurrence of vertigo between 3 and 6 months after the second injection and went on to one additional dose of gentamicin. At 2 years follow-up, 10 patients (91%) had complete and 1 (9%) substantial control of vertigo; 3 subjects (27%) had hearing decreased. Tinnitus disappeared or decreased in 3 patients (27%); eight subjects (73%) reported their aural pressure abolished or decreased. The present study demonstrates that in patients with Ménière's disease, 0.5 mL gentamicin solution, with a concentration of 80 mg/mL (total dose < or = 80 mg), injected intratympanically once a week after having obliterated the round-window niche, permits complete or substantial control of vertigo in two-thirds of cases after two doses and in all subjects after three doses. This vertigo control rate is compared to that observed after vestibular nerve section. Hearing results are not different from those with natural control, with endolymphatic sac surgery, and with vestibular nerve section.

Adult↗
PubMed2004

Novel slow- and fast-type drug release round-window microimplants for local drug application to the cochlea: an experimental study in guinea pigs.

Novel drug release microimplants (0.8 x 1.14 mm; custom-made by Leiras, now Schering OY, Finland) of slow- and fast-release types containing either 0.9 mg beclomethasone or no drug at all were placed unilaterally onto the round-window membrane (RWM) of 45 guinea pigs for a maximum duration of 28 days. The following parameters were tested on days 1, 14 and 28 after implantation: threshold levels of beclomethasone in the perilymph of the scala tympani, auditory brain stem responses (ABR thresholds and ABR threshold shifts), RWM morphology and hair cell loss (cytocochleograms). None of the animals in the non-implanted control group (n = 5) or placebo implant group (n = 15), but all animals in the slow-release-type implant group (n = 15) and fast-release-type implant group (n = 15) revealed the presence of beclomethasone on day 1 (34.9 and 64.3 pg/microl, respectively), day 14 (43.8 and 46.9 pg/microl, respectively) and day 28 after implantation (4.7 and 60.5 pg/microl, respectively). Histology of the RWMs appeared normal, and cytocochleograms revealed no inner hair cell loss and outer hair cell loss within normal ranges (from 0.5 +/- 0.4 to 0.8 +/- 0.2% per cochlea) in both ears in all experimental groups at any time during examination (days 1, 14 and 28). Initial values of ABR thresholds at 3, 6, 9 and 12 kHz did not differ significantly in any of the experimental groups. In non-implanted controls, no significant differences of ABR thresholds were observed in all frequencies tested in either ear on days 1, 14 and 28 compared to initial values, and ABR threshold shifts ranged from -3 +/- 5 dB (min.) to +5 +/- 7 dB (max.). On day 28 after implantation, there were no significant differences of ABR threshold shifts between this and the implant groups, except for 6 kHz of the slow-release device. Therefore, the placebo implants, the slow-release and the fast-release beclomethasone implants appear suitable for further experiments.

Animals↗
PubMedDate not supplied

Middle and inner ear: improved depiction with multiplanar reconstruction of volumetric CT data.

Many anatomic structures of the middle and inner ear are not optimally depicted at computed tomography (CT) with image reconstruction in the standard axial and coronal planes. Recent advances in multidetector CT, including the development of scanners with 32 detector rows, allow the acquisition of isotropic voxels that can be reconstructed in any plane of section. This technique gives radiologists the opportunity to visualize the anatomic structures of the middle and inner ear (the ossicular chain, stapedial footplate-oval window complex, round window, cochlea, vestibular aqueduct, and bones of the superior semicircular canal and facial nerve canal) in greater detail and may help increase the accuracy of CT for the diagnosis of diseases of the middle and inner ear.

Ear Diseases↗
PubMed2001

Electrically evoked otoacoustic emissions from apical and basal perilymphatic electrode positions in the guinea pig cochlea.

Stimulation of the cochlea with sinusoidal current results in the production of an otoacoustic emission at the primary frequency of the stimulus current. In this study we test the hypothesis that the wide frequency response from round window (RW) stimulation is due to the involvement of a relatively large spatial segment of the organ of Corti. Tonotopically organized group delays would be evident from perilymphatic electrode locations that restrict the spatial extent of hair cell stimulation. Monopolar and bipolar-paired stimulus electrodes were placed in perilymphatic areas of the first or third cochlear turns and the electrically evoked otoacoustic emissions (EEOAE) produced by these electrodes were compared to that from the RW monopolar electrode in the anesthetized guinea pig. Current stimuli of 35 microA RMS were swept across the frequency range between 60 Hz and 100 kHz. The EEOAE was measured using a microphone coupled to the ear canal. It was found that the bandwidth of EEOAEs from RW stimulation extended to at least 40 kHz and was a relatively insensitive to electrode location on the RW. The group delay of the EEOAE from stimulation at the RW membrane (corrected to stapes motion) was about 53 micros. First and third turn stimulations from electrode placements in perilymph near the bony wall of cochlea yielded narrower band EEOAE magnitude spectra but which had the same short group delays as for RW stimulation. A confined current (from a bipolar electrode pair) applied close to the basilar membrane (BM) in the first turn produced the narrowest frequency-band magnitude emissions and a mean corrected group delay of 176 micros for a location approximately 3 mm from the high frequency end of the BM (corresponding to about the 18 kHz best frequency location). Bipolar electrodes in the third turn scala tympani produced low pass EEOAE magnitude functions with corrected group delays ranging between approximately 0.3 and 1 ms. The average phase slopes did not change with altered cochlear sensitivity and postmortem. These data indicate that the EEOAE from RW stimulation is the summed response from a wide-tonotopic distribution of outer hair cells. A preliminary model study indicates that short time delayed emissions are the result of a large spatial distribution of current applied to perilymphatic locations possibly giving rise to "wave-fixed" emissions.

Animals↗
PubMedDate not supplied

Morphology of the seagull's inner ear.

The morphology of the seagull ear was investigated and found to be generally similar to that of other Aves. Several specific outer middle and inner ear features were found to be sufficiently different as to be remarkable. Most notably, the dual membranes of the external auditory meatus: one, a collecting (and possibly amplifying and reflecting) parabolic membrane chamber situated immediately anterior to the slightly deeper tympanic membrane. The convex tympanic membrane attaches a cartilagenous extracolumella and a thick osseous columella, which is less thin and fragile than that observed in domestic fowl of comparable body size. The columella footplate and round window are completely covered with a second middle ear membrane which apparently serves as an H2O seal and hydrostatic pressure matcher. The short, hard seagull cochlea houses an elaborate basilar papilla which contains thousands of short and tall hair cells, each with a systematic arrangement of stereocilia bundles. In the seagull, the length of the basilar papilla and the length, width, and number of stereocilia, features which affect the transduction process and frequency resolution, are different from those reported for certain other Aves.

Animals↗
PubMed1999

Responses of auditory nerve fibers innervating regenerated hair cells after local application of gentamicin at the round window of the cochlea in the pigeon.

Hair cells in the basilar papilla of birds have the capacity to regenerate after injury. There is also functional recovery of hearing after regeneration of the hair cells. The present study was undertaken to determine the effect of local aminoglycoside application on the physiology of auditory nerve fibers innervating regenerated hair cells. Collagen sponges loaded with gentamicin were placed at the round window of the cochlea in adult pigeons. The local application of gentamicin-loaded collagen sponges resulted in total hair cell loss over at least the basal 62% of the basilar papilla. According to the pigeon cochlear place-frequency map (Smolders, Ding-Pfennigdorff and Klinke, Hear. Res. 92 (1995) 151-169), frequencies above 0.3 kHz are represented in this area. Physiological data on single auditory nerve fibers were obtained 14 weeks after gentamicin treatment. The response properties showed the following characteristics when compared to control data: CF thresholds (CF = characteristic frequency) were elevated in units with CF above 0.15 kHz, sharpness of tuning (Q10dB) was reduced in units with CF above 0.38 kHz, low-frequency slopes of the tuning curves were reduced in units with CF above 0.25 kHz, high frequency slopes of the tuning curves were reduced in units with CF above 0.4 kHz, spontaneous firing rate was reduced in units with CF above 0.38 kHz, dynamic range of rate-intensity functions at CF was reduced in units with CF above 0.4 kHz and the slopes of these rate-intensity functions were elevated in units with CF above 0.4 kHz. Maximum discharge rate was the only parameter that remained unchanged in regenerated ears. The results show that the response properties of auditory nerve fibers which innervate areas of the papilla that were previously devoid of hair cells are poorer than the controls, but that action potential generation in the afferent fibers is unaffected. This suggests that despite structural regeneration of the basilar papilla, functional recovery of the auditory periphery is incomplete at the level of the hair cell or the hair cell-afferent synapse.

Administration, Topical↗
PubMed1980

Histopathological changes in the temporal bone in kwashiorkor.

The histopathological changes in human temporal bones are described for 2 cases of kwashiorkor--a protein/calorie malnutrition (PCM) state. There is photographic evidence of severe damge to the middle and inner ears and to the vestibulocochlear nerve. The middle ear shows evidence of chronic otitis media, a common clinical finding in kwashiorkor. Significantly, the round window membranes in both cases showed thickening and infiltration with inflammatory cells. The inner ear showed the loss of cellular elements and hair cell loss in the spiral organ. A marked decrease of spiral ganglion cells and demyelination of the vestibulocochlear nerve were also seen.

Adolescent↗
PubMed2002

Pharmacologic treatment of inner ear: from basic science to the patient.

Most of the deafness are of sensorineural origin and are characterized by a loss of hair cells and of spiral ganglion neurons. At the present time, hearing aids are the only treatment. However, in some diseases of the inner ear, pharmacological treatment have been proposed and used successfully. In this paper, we will review some basic science aspects of the biology of the neurosensory structures of the inner ear, in particular of the auditory neurons, that lead to the rationale of some treatments for the inner ear diseases. Developmental studies, neuronal cell culture experiments, and analyses of gene knockout animals reveal a number of growth factors which are important for the rescue and repair of injured auditory neurons in the inner ear. These factors rescue the injured auditory neurons in vivo. Furthermore, perfusion of antioxydant to the cochlea prevented the hearing loss induced by cisplatin. These in vitro and in vivo experiments demonstrate that it is possible to manipulate the neurosensory structures of the inner ear and provide an effective treatment to prevent the degeneration of the neurons. The molecules or drugs can be administered locally to the inner ear through a direct perilymphatic perfusion or through the round window membrane. As an example, we will discuss the treatment of patients suffering from idiopathic sensorineural hearing loss which can be treated successfully by a perfusion through the round window membrane, improving their hearing threshold and their speech discrimination.

Animals↗
PubMedDate not supplied

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.

Animals↗
PubMed1994

Cochlear implantation in children: labyrinthitis following pneumococcal otitis media in unimplanted and implanted cat cochleas.

Pneumococcal otitis media is frequent in young children and could lead to labyrinthitis post-implantation. To assess the risk, and methods of minimizing it by a graft to the round window around the electrode entry point, we have used a cat animal model of pneumococcal otitis media. Twenty-one kittens were used in the study. Thirty-two cochleas were implanted when the kittens were 2 months of age. Fourteen cochleas were implanted without using a graft (12 were available for study); 9 had a fascial graft, and 9 a Gelfoam graft (7 were available for study). The implanted kittens had their bullae inoculated with Streptococcus pneumoniae 2 months after implantation and were sacrificed 1 week later. There were also 9 unimplanted control ears which were inoculated when the animals were 4 months of age. Labyrinthitis occurred in 44% of unimplanted control, 50% of implanted ungrafted, and 6% of implanted grafted (fascia and Gelfoam) cochleas. There was no statistically significant difference between the unimplanted control and the implanted cochleas (p < 0.05). There was, however, a difference between the implanted-ungrafted and implanted grafted cochleas, but not between the use of fascia and Gelfoam to graft the round window entry point. As a result, the data indicates that cochlear implantation does not increase the risk of labyrinthitis following pneumococcal otitis media, but it is desirable to use fascia as a graft to the round window around the electrode entry point.

Animals↗
PubMed2003

Effects of chronic furosemide treatment and age on cell division in the adult gerbil inner ear.

Atrophy of the stria vascularis and spiral ligament and an associated decrease in the endocochlear potential (EP) are significant factors in age-related hearing loss (presbyacusis). To model this EP decrease, furosemide was delivered into the round-window niche of young adult gerbils by osmotic pump for seven days, chronically reducing the EP by 30-40 mV. Compound action potential (CAP) thresholds were correspondingly reduced by 30-40 dB SPL at high frequencies. Two weeks after withdrawal of furosemide, the treated ears showed an EP recovery of up to 20-30 mV along with a similar recovery of CAP thresholds. The influence of cell division on furosemide-induced and age-related decline of the EP was examined using a mitotic tracer, bromodeoxyuridine (BrdU). Cell proliferation was examined in three groups: young control, furosemide-treated, and aged cochleas. Sections immunostained for BrdU were bleached with H2O2 to eliminate ambiguities with melanin pigment in the inner ear. Cell types positively labeled for BrdU in all three groups included Schwann cells in Rosenthal's canal; glial cells in the osseous spiral lamina; fibrocytes in the limbus, sacculus, and spiral ligament (SL); epithelial cells in Reissner's and round-window membranes; intermediate cells in the stria vascularis; and vascular endothelial cells. Quantitative analysis showed that the mean number of BrdU-positive (BrdU+) intermediate cells in the stria did not differ significantly among the three groups. In contrast, there was a significant increase of BrdU + fibrocytes in the SL of furosemide-treated animals as compared to the young control group. Moreover, there was a significant decrease in labeled fibrocytes in the aged versus the young ears, particularly among the type II and type IV subtypes. The results suggest that the increased fibrocyte turnover in the SL after furosemide treatment may be related to the recovery of EP and CAP thresholds, supporting the hypothesis that fibrocyte proliferation may be essential for maintaining the EP and cochlear function in normal and damaged cochleas. Moreover, the decreased turnover of SL fibrocytes with age may be a contributing factor underlying the lateral wall pathology and consequent EP loss that often accompanies presbyacusis.

Action Potentials↗