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Results for “Round Window, Ear”

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PubMed1995

Anomaly of the facial nerve and cochlear implantation.

The incidence of preoperative damage to the facial nerve in cochlear implantation is very low. The course of the facial nerve is not routinely evaluated preoperatively, but variations in its course can restrict access to the round window and impede implantation. In 5 of 42 operations, direct visualization of the round window was not possible. In 1 patient there was an obvious congenital bifurcation. Successful implantation was made possible by mobilizing the nerve.

Adult↗
PubMed1994

[Effect of hypoxia at 5% oxygen on global electrophysiological responses from normal awake guinea pigs].

All experiments were conducted on awake guinea pigs warranting a normal physiological function of the circulatory system. Global electrophysiological responses from the round window of cochlea were monitored: cochlear microphonic (CM), summating potential (SP) and auditory compound action potential (AP). The results showed that hypoxia induced a threshold elevation at all frequencies thus affecting the whole cochlea, and also very large diminutions of AP at high intensity level exclusively in response to a high frequency, and very large increases of SP at 2 kHz and 8 kHz. After hypoxia, which lasted thirty minutes, a considerable recovery occurred, and at the end of the session recovery reached around eighty percent. Alterations of cochlea action potential in response to high intensity stimuli were dissociated from threshold changes. We speculate that threshold elevation could be associated with over-all energetic (ATP) decrease leading to diminution of endolymphatic resting potential. Action potential changes at high intensity and at cochlear base could reflect neurotransmission (afferent, efferent or sympathetic) disturbance.

Action Potentials↗
PubMed1994

[Rupture of the round window. Differential diagnosis in sudden deafness and acute vestibular symptoms].

Rupture of the round window has to be considered in the differential diagnosis of sudden hearing loss with or without vertigo. The symptoms of this pathology vary a lot. No clinical examination with a sufficiently high selectivity and sensibility exists. The low therapeutical risk is stressed: exploratory and therapeutic tympanoscopy with grafting of the round and/or oval window.

Evoked Potentials, Auditory, Brain Stem↗
PubMed1994

[Test of electrical stimulation of the round window. Diagnostic and prognostic value of the rehabilitation of total deafness by cochlear implant].

The round window electrical stimulation (RWES) test has been performed in 708 cases of total deafness. Among them 244 have successfully benefited with a cochlear implant. Electrical Brain Stem Evoked (EBSE) potential elicited by this stimulation have been registrated in 283 cases, 113 of them during general anesthesia necessary in children. This test supplies the patient with a subjective sound sensation and/or EBSE in 93% of cases. The correlation between electrical data of this RWES test and clinical results of the cochlear implant is described. This test is discussed regarding the simple transtympanique promonotory stimulation test.

Adolescent↗
PubMed1995

CT of postmeningitic deafness: observations and predictive value for cochlear implants in children.

PURPOSE: To demonstrate CT abnormalities encountered in children with postmeningitic deafness and to assess the value of CT in the prediction of cochlear implantation difficulties. METHODS: Thirteen children with postmeningitic deafness were evaluated with high-resolution, thin-section CT. CT findings were correlated with surgical anatomy at the time of cochlear implantation, with particular regard to the prediction of implant success. RESULTS: CT findings included normal scans (3 of 13, 23.1%), cochlear stenosis (5 of 13, 37.7%), cochlear fibroossific change (1 of 13, 7.7%), cochlear ossification (4 of 13, 30.8%), and osseous hypertrophy at the round window niche (4 of 13, 30.8%). Nine of 10 patients with abnormal findings had incomplete or difficult implantations (90%); 7 (88.8%) of these 9 received limited electrode insertions. CONCLUSION: Attention to subtle otological abnormalities on thin-section CT is helpful in the prediction of early success or failure of implantation in children with postmeningitic deafness. Those with CT abnormalities had a 90% risk of incomplete or difficult insertions with a 70% chance of limited electrode insertion.

Adolescent↗
PubMed1994

Prognostic value of round-window psychophysical testing with cochlear-implant candidates.

The preimplant, psychophysical-test results obtained with a single-ball, round-window electrode for 32 peri- or postlingually deafened, adult, Nucleus 22-channel cochlear-implant users were analyzed and correlated with their postimplant, open-set, speech recognition performance. The results revealed that some preimplant measures do have value as predictors of speech recognition abilities in this group of subjects. All subjects used the MPEAK speech-coding strategy and had been using their device for at least 6 months. The psychophysical measures that were found to correlate most highly with postimplant performance included the detection threshold at 400 Hz and the threshold slope function from 50 to 400 Hz, with lower values associated with higher speech recognition. To a lesser extent, detection thresholds at 100 and 200 Hz, the dynamic range at 200 and 400 Hz, and the gap detection threshold at 100 Hz correlated with speech performance. As well, duration-of-deafness variables were found to correlate significantly with postimplant performance.

Adult↗
PubMed1993

[Cochlear histopathological changes following chronic extracochlear electrical stimulation in kittens].

Histopathological investigation of the cochlea following chronic extracochlear electrical stimulation was carried out in 5 kittens. The auditory nerves were electrically stimulated with round window or tympanic promontory electrodes for periods of 1276-1526 h using charge-balanced biphasic current pulses at charge densities of 1.27-5.73 microC/cm2. geom. phase. The histopathological changes were examined with a light microscope. The findings were as follow: 1. The fixations of round window and tympanic promontory electrodes were very firm. Six round window membranes became thicker in the area which contacted the electrode. One was pushed into the scala tympani and adhered to the spiral lamina of the hook region. 2. There was some outer hair cell loss, mild inner hair cell loss and disappearance of Corti's organ structures in a small area of lower basal turns. 3. Decrease of spiral ganglion cell density was found over a 2% basilar membrane length in 2 stimulated cochleas. 4. There was no change in normal control cochleas. These results indicate that mild histopathological changes occurred even though chronic electrical stimulation was performed with non-invasive extracochlear electrodes. The mechanism behind these changes should be further investigated.

Animals↗
PubMed1994

Effect of perilymphatic fistulas on evoked otoacoustic emissions in the guinea pig.

Round window perilymphatic fistulas were surgically created in 20 guinea pigs. Distortion product otoacoustic emissions (DPOAEs) at 2fl - f2 were recorded prior to and immediately following laceration of the round window. The stimuli were equal level sinusoids (f1 < f2) with f2 ranging from 2 to 10 kHz, a fixed f2:f1 ratio of 1.25, and stimulus levels (L2 = L1) ranging from 20 to 80 dB SPL. After an 18-day survival period, emission measurements were repeated, and fluorescein was infused into the cerebrospinal fluid to verify patency or closure of the fistula. Nine animals demonstrated patent fistulas, whereas 11 had closed fistulas. There was a statistically significant reduction in DPOAE amplitude after an acute fistula across all stimulus levels (p < .001). At 18 days the DPOAE amplitudes in animals with healed fistulas could not be differentiated from controls, whereas DPOAE amplitudes in animals with patent fistulas were statistically different from controls (p < .05). The results suggest that evoked otoacoustic emissions may be useful in detecting perilymphatic fistulas.

Acoustic Stimulation↗
PubMed1997

[Cochleoscopy].

Explore the source record for details and available documents.

Animals↗
PubMed1998

[Variability of the round window niche entry in children and adults].

The round window niche entry (fossula fenestrae cochleae, fossula fenestrae rotundae) is one of the main structures in the labyrinthine wall of the tympanic cavity. Its variability is fairly significant and very important in otosurgery. In order to learn more about the morphology of the round window niche entry, a microanatomical study on 100 temporal bones obtained from cadavers aged 0-71 y. was performed. A standard set of otosurgical equipment was used. Five morphological forms of the round window niche entry were differentiated: triangular, semicircular, ovally horizontal, ovally vertical and round ones. Triangular forms were observed only in children of over 4 years of age and round forms almost only in young children, of age below this borderline (the beginning of pneumatization of the temporal bone). The differences between these two groups were statistically significant.

Adolescent↗
PubMed2003

Adenoviral vector gene delivery via the round window membrane in guinea pigs.

We have found that damage from a local anesthetic solution containing phenol permitted beta-galactosidase (beta-gal) gene delivery to the guinea pig inner ear via the round window membrane (RWM). RWM damage was evident as degeneration of the outer epithelium. After adenovirus lacZ vector was applied to the damaged RWM, immunohistochemistry showed strong beta-gal expression in the RWM, mesothelial cells, organ of Corti, spiral limbus, spiral ligament and spiral ganglion. In the vestibular labyrinth, expression was seen in the sensory and supporting cells, transitional cells, and the dark-cell area. Thus, adenovirus can transfect a variety of inner ear cells in the guinea pig through a damaged RWM.

Adenoviridae↗
PubMed1980

Permeability of the middle ear to staphylococcal pyrogenic exotoxin in otitis media.

Middle ear permeability after instillation of staphylococcal pyrogenic exotoxin was studied in each of 12 cats, 6 of them with otitis media induced by obstructing their eustachian tubes. This is the first report that there is passage of toxin to the perilymph, cerebrospinal fluid and blood not only in diseased ears, but also in normal controls, 25 min and 12 h after exposure of the middle ear cavity and round window membrane to toxin. The data suggest a pathophysiological explanation for the association of otitis media and sensorineural hearing loss and/or endolymphatic hydrops; potentially both entities can be caused by exotoxins. It also documents the extraordinary capabilities of movement of staphylococcal exotoxin.

Animals↗
PubMed1997

Fast, slow, and steady-state effects of contralateral acoustic activation of the medial olivocochlear efferent system in awake guinea pigs: action of gentamicin.

The function of the medial olivocochlear efferent system was observed in awake guinea pigs by recording, in the absence of ipsilateral external acoustic stimulation, the ensemble background activity (EBA) of the VIIIth nerve from an electrode chronically implanted on the round window of one ear. The EBA was measured by calculating the power value of the round window signal in the 0.5- to 2.5-kHz band after digital or analog (active) filtering. This EBA was compared with and without the addition of a low-level broadband noise to the opposite ear. The contralateral broadband noise (CLBN, 55 dB SPL) induced, via the efferent system, a decrease (suppression) of this EBA. With the use of noise bursts of different durations, two components in this suppression could be observed. After the onset of a 1-s CLBN, the power value of the EBA decreased rapidly by 38.0 +/- 4.2% (mean +/- SD, n = 3), with a latency of <10 ms and a decay time constant of 13.1 +/- 1.0 ms (fast effect). At the offset of the 1-s CLBN, EBA came back to prestimulation values with a similar latency and a time constant of 15.5 +/- 2.9 ms. During longer CLBN stimulation (>/=1 min), EBA presented, after the fast decrease, an additional, slower decrease of 15.6 +/- 3.1%, with a delay of 9.8 +/- 1.3 s and a decay time constant of 16.1 +/- 5.0 s (n = 12, slow effect), and then remained remarkably constant for as long as observed, i.e., >2 h (steady state). The average global suppression was thus up to 47.8 +/- 5.8% of the basal, pre-CLBN-stimulation EBA value. At the offset of the CLBN, EBA returned to pre-CLBN level with fast and slow phases, with, for the slow phase, no delay and a time constant of 32.1 +/- 8.1 s. Fast and slow changes in EBA power values were observed after a single injection of gentamicin (GM) at different doses (150, 200, and 250 mg/kg). At 150 and 200 mg/kg, GM progressively and reversibly blocked the rapid effect, but the slow component of the efferent medial suppression remained remarkably unchanged. However, at higher doses both the fast and slow suppressions were totally yet still reversibly blocked. These observations indicate that the medial olivocochlear efferent system exerts sustained influences on outer hair cells and that this effect develops in two different steps that may have different basic cellular mechanisms.

Acoustic Stimulation↗
PubMed1989

Hydrocortisone applied into the round window niche causes electrophysiological dysfunction of the inner ear.

A suspension of 2% hydrocortisone, micronized in sterile water, was instilled through a perforation in the tympanic membrane into the round window (RW) niche of 9 healthy rats once a day for 5 consecutive days. Three animals were used as controls, and were exposed to sterile water only instilled into the RW niche. Auditory brainstem response (ABR) thresholds were determined for eight frequencies: 2, 4, 6, 8, 12, 16, 20 and 31.5 kHz. Hydrocortisone caused impaired ABR thresholds in the frequency range of 12-31.5 kHz after 5 days of instillation. The impaired thresholds remained unchanged for 2 months, indicating irreversible electrophysiological changes in the inner ear. No morphological damage could be detected in the cochlea by means of light microscopy or transmission electron microscopy. However, hydrocortisone delayed the healing of the perforated tympanic membrane.

Animals↗
PubMed1988

Impaired hearing following instillation of hydrocortisone into the middle ear. Preliminary report from an animal study.

The effect of cortisone on the inner ear function was investigated. A suspension of 2% hydrocortisone in sterile water was instilled into the middle ear in the round window niche area of healthy rats. The hearing for eight frequencies was determined by auditory brainstem response (ABR) measurements. After 5 days of daily local application, ABR thresholds impaired in the high-frequency range 12 to 31.5 kHz. The impaired ABR thresholds remained unchanged throughout 3 weeks of observation, indicating irreversible damage to the inner ear. It is also noteworthy that hydrocortisone delayed healing of the perforated tympanic membrane.

Animals↗