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PubMed1982

Exploratory tympanotomy revisited.

The history of exploratory tympanotomy is somewhat obscure. Methods and findings of exploratory tympanotomy were described and assessed for unexplained conductive and occasional sensorineural hearing losses. Of 316 recent cases positive findings leading to diagnosis and therapy occurred in all 250 cases of conductive hearing losses and in 43 of 63 cases of sensorineural hearing losses. In decreasing order of occurrence findings were sequelae of otitis media, otosclerosis, oval and round window changes including perilymph leakage, congenital and traumatic fixation and disarticulation of ossicles. These observations and indications are discussed.

Ear Diseases↗
PubMed1990

[Effects of endotoxin on the cochlear electrophysiology and Na(+)-K(+)-ATPase activity].

Hemophilus influenzae (type B) endotoxin 10 micrograms was put in the niche of the round window in guinea pigs. The CAP thresholds and N1 latencies were measured before and 12, 24 and 72 hours after experiments. The 10 kHz and 8 kHz CAP thresholds after experiments were significantly higher (P less than 0.01), the N1 latencies were prolonged (P less than 0.05). There were minute changes in 4kHz CAP thresholds and N1 latencies (P greater than 0.05). In all time groups, the Na(+)-K(+)-ATPase activity was outstandingly weakened. It suggested that: (1) endotoxin put in the niche of the round window is responsible for the cochlear function disturbances in high frequencies, and (2) the decrease of the Na(+)-K(+)-ATPase activity is an important factor for the electrophysiological disturbances in the inner ear.

Animals↗
PubMed1988

The effects of cetrimide and potassium bromate on the potassium ion concentration in the inner ear fluid of the guinea-pig.

The mammalian inner ear is located deep within the temporal bone. The organ of Corti, the delicate sensory system for sound, is surrounded by two fluid systems; the potassium-rich endolymph and the sodium-rich perilymph. The pathogenesis of inner ear deafness is thought to be largely due to an imbalance of potassium and sodium ions in the inner ear fluids. Dynamic changes in K+ in the endolymph and perilymph were studied in the guinea-pig following cetrimide (cetrimonium bromide, a powerful cationic detergent which shows ototoxicity) applications on the round window membrane, intramuscular injection of potassium bromate (bread whitener, known to cause renal damage and permanent deafness in animals and man). Maximum fall in K+ concentration in the endolymoh (mM/min) and maximum K+ conductance (mM/min/mV) were 3.54 +/- 1.65 and 0.036 +/- 0.02 in cetrimide, and 1.85 +/- 0.35 and 0.021 +/- 0.009 in potassium bromate, respectively. In view of these findings, the influence of the active transport mechanism to K+ concentrations are discussed in comparison with dynamic changes in endolymph K+ induced by asphyxia and ethacrynic acid.

Animals↗
PubMed1976

[Surgery of inner ear diseases (author's transl)].

In the treatment of Menière's disease, surgical procedures are available when conservative measures have failed. The most distressing symptom of vertigo can frequently be arrested, tinnitus reduced and hearing improved. Sudden deafness due to round window rupture is treatable. The most important disorder with labyrinthe symptoms is the acoustic neuroma, the smaller ones of which can be operated on by otologists in collaboration with neurosurgeons using the transtemporal or translabyrinthine approach with preservation of the facial nerve.

Humans↗
PubMed2003

Evidence for surviving outer hair cell function in congenitally deaf ears.

OBJECTIVES/HYPOTHESIS: The hypotheses of the study were that congenital hearing impairment in infants can result from the isolated loss of inner hair cells of the cochlea and that this is shown by the presence of abnormal positive summating potentials on round window electrocochleography. The objectives were to establish the proportion of infants with hearing loss affected, the nature of the cochlear lesion, and its etiology. And to highlight the important implications for otoacoustic emissions testing and universal neonatal screening. STUDY DESIGN: A prospectively conducted consecutive cohort study with supplemental review of notes was performed. METHODS: Four hundred sixty-four children underwent round window electrocochleography and auditory brainstem response testing under general anesthesia to assess suspected hearing loss. The presence of abnormal positive potentials was recorded. Otoacoustic emissions data were collected separately and retrospectively. RESULTS: Three hundred forty-two children had significant bilateral congenital hearing loss. All results were from hearing-impaired children. Abnormal positive potentials were recorded in 73 of 342 children (21%). Eighty-three percent of children with otoacoustic emissions also had abnormal positive potentials, but only 14% of children without otoacoustic emissions had abnormal positive potentials (P <.001). In the neonatal intensive care unit setting, 43% of infants were found to have abnormal positive potentials, whereas only 10% had abnormal positive potentials if not in the neonatal intensive care unit setting (P <.001). Abnormal positive potentials were present in 63% of infants born before 30 weeks gestation and in 14% of infants born at term (P <.001). Abnormal positive potentials were identified in 57% of infants with documented hypoxia and 11% of children with no episodes (P <.001). Otoacoustic emissions were present in 48% of infants from the neonatal intensive care unit, despite their hearing loss. CONCLUSION: Both otoacoustic emissions and abnormal positive potentials may originate from outer hair cell activity following inner hair cell loss. This may occur in more than 40% of hearing-impaired children in the neonatal intensive care unit setting. Chronic hypoxia is the most likely cause. Otoacoustic emissions testing may not be a suitable screening tool for such infants.

Audiometry, Evoked Response↗
PubMed2005

Cochlear implantation in rats: a new surgical approach.

The laboratory rat has been used extensively in auditory research but has had limited use in cochlear implant related research due mainly to the surgically restricted access to the scala tympani. We have developed a new surgical method for cochlear implantation in rats. The key to this protocol was cauterizing the stapedial artery (SA) and making a small cochleostomy near the round window in order to enlarge the surgical access to the scala tympani. Five normal hearing Hooded Wistar rats were used to investigate the effect of cauterizing the SA on hearing and auditory nerve survival. Results showed that cauterizing the SA was surgically feasible, afforded excellent exposure of the round window niche for cochleostomy, and did not adversely affect acoustic thresholds measured electrophysiologically. Moreover, there was no difference in spiral ganglion cell densities for any cochlear turn when compared with the contralateral control ears. Three deafened rats were subsequently implanted with a scala tympani electrode array using this new surgical approach. Electrically evoked auditory brainstem responses using bipolar stimulation, and subsequent cochlear histopathology demonstrated that cochlear implantation using a custom-made rat electrode array was safe and effective. The surgical approach presented in this paper presents a safe and effective procedure for acute or chronic cochlear implantation in the rat model.

Animals↗
PubMed2003

Electrical suppression of tinnitus with high-rate pulse trains.

HYPOTHESIS: Application of high-rate pulse trains (e.g., 4800 pps) to the cochlea may represent an effective treatment of tinnitus. BACKGROUND: Tinnitus is a widespread clinical problem with multiple treatments but no cure. A cure for tinnitus would restore the perception of silence. One plausible hypothesis for the origin of tinnitus associated with sensorineural hearing loss is that it is due to loss or alteration of the normal spontaneous activity in the deafferented regions of the cochlea. Electrical stimulation of the cochlea with 5000-pps pulse trains can produce spontaneous-like patterns of spike activity in the auditory nerve. METHODS: Eleven volunteer human subjects with bothersome tinnitus and high-frequency sensorineural hearing loss underwent myringotomy and temporary placement of a round window electrode. High-rate pulse train stimuli were presented at various stimulus intensities and tinnitus, and stimulus perception were scaled by the subject. Three cochlear implant recipients with tinnitus in the implanted ear underwent similar stimulation. RESULTS: Five of 11 (45%) of transtympanic subjects showed substantial or complete tinnitus suppression with either no perception or only a transient perception of the stimulus. Three showed tinnitus suppression only in association with the perception of the stimulus. Three showed no effects on tinnitus. A similar pattern of responses was seen in the cochlear implant subjects. CONCLUSIONS: Although the study lacked an ideal placebo control, the results are promising and support further research to develop a clinically useful intervention for this troubling disorder.

Adult↗
PubMedDate not supplied

Effect of increased perilymphatic pressure on endocochlear potential.

A study was done to determine how increased fluid pressure in the inner ear influences cochlear blood flow. Hydrostatic pressure was applied to the scala vestibuli or scala tympani in guinea pigs. Endocochlear potential, which is sensitive to the lack of oxygen, was measured through the round window membrane or through the stria vascularis. Cochlear blood flow was confirmed by intravenous injection of India ink. When the perilymphatic pressure was raised to a relatively high level, endocochlear potential decreased, ina similar way as in response to anoxia, because of the cessation of the cochlear blood flow. This change was completely reversible upon applications of pressure for brief periods of time. We consider that the cochlear blood flow ceases when the fluid pressure reaches the level of intracochlear arterial pressure.

Animals↗
PubMed1991

Medical imaging in cochlear implant candidates.

A retrospective study of preoperative radiographic surveys obtained in 85 cochlear implant patients was performed. A total of 90 cochlear implant patients were seen at our institution during the last 10 years. In three, the implant was placed at another institution. In two otosclerosis patients, no preimplant radiographic examination was obtained. Meningitis was the cause of deafness in 45 of 90 patients (50 percent); 28 of 40 pediatric age group patients (70 percent), and in 17 of 50 adult patients (34 percent). Thirty-three of 45 postmeningitis patients (73 percent) showed characteristic radiographic signs of sclerosing labyrinthitis or labyrinthitis ossificans. These signs were present in only one other patient who was deaf with unknown cause. Deformity of the inner ear sufficient to explain congenital deafness was noted in three cases; one Mondini deformity and two obliterated base of the cochlea (modiolus). Three otosclerosis patients who had preimplant radiographs, and one congenital syphilis patient showed classic radiographic signs of their respective diseases. Obliteration or stenosis of the round and/or the oval windows were observed in 26 cases drawn from all major etiologic groups. State-of-the-art high resolution, thin-section CT can demonstrate subtle changes that may be the only clue to the cause of deafness. MRI promises to be a useful technique to follow meningitis patients with membraneous labyrinth changes progressing to sclerosing labyrinthitis.

Adolescent↗
PubMed1977

[On the effect of hyperbaric oxygen (OHP) at the guinea pig's cochlea insulted by hypoxia (author's transl)].

The effect of OHP (oxygen under high pressure) by examining 17 CO-intoxicated guinea pigs. The following effects have been observed: The microphonics recovered significantly faster after hypoxia caused by CO than under air. Hyperbaric oxygen has a protecting effect on the inner ear. If OHP is applicated before CO, the microphonics decrease less than under normal breathing. The postmortal microphonics increased to a level above the known postmortal slope, suggesting a diffusion of oxygen through the round window.

Action Potentials↗
PubMed2003

Changes in CAP adaptation in experimentally induced endolymphatic hydrops.

OBJECTIVE: To determine the effect of experimentally induced endolymphatic hydrops (ELHs) on compound action potential (CAP) adaptation. METHODS: The CAP was recorded 1 month after surgical treatment to produce ELH. The CAP threshold in response to click stimuli showed no significant differences between the hydropic and control groups. The CAP was elicited from the retroauricular-exposed round window using a silver ball electrode. Click trains consisting of 10 clicks with an interclick interval (Deltat) of either 4 or 8 ms were delivered through a loudspeaker placed in front of the animals' ears. The patterns of adaptation to these click trains were evaluated as functions of Deltat and intensity level. RESULTS: An abnormal pattern of CAP adaptation was observed in hydropic ears. CONCLUSIONS: These findings suggest that early ELH influences CAP adaptation.

Acoustic Stimulation↗
PubMed1992

Spontaneous remission in experimental autoimmune labyrinthitis.

We investigated the time course of hearing impairment and cellular infiltration into the inner ear after systemic sensitization of guinea pigs with a single intradermal injection of bovine inner ear antigen (IEAg) in complete Freund's adjuvant (CFA). Lymphocytes and polymorphonucleocytes appeared mainly in the scala tympani on days 7 to 14, and in addition there was thickening and cellular infiltration of the round window membrane at day 14. These cellular infiltrations resolved after day 28. The auditory brain stem response thresholds from IEAg-sensitized animals were significantly elevated after day 7. Some sensitized animals (n = 5) had spontaneous remissions after day 28; however, the hearing thresholds did not completely recover. These results demonstrate that experimental autoimmune labyrinthitis can be induced by a single inoculation of IEAg-CFA and that remission, as evidenced by clearing of the cochlear cellular infiltration and improved hearing thresholds, can occur spontaneously.

Animals↗
PubMed1995

Acoustic stimulation of the semicircular canals.

Stimulation of the semicircular canals provides an alternative method of vibratory stimulation of the auditory system. The frequency response characteristics of stimulation of the tympanic membrane, malleus, stapes, round window, and fenestrated semicircular canal are presented in this article.

Animals↗
PubMed1993

The vascular component of sodium salicylate ototoxicity in the guinea pig.

Drugs of the salicylate family (aspirin-like drugs) are reversibly ototoxic. Electrophysiologic and ultrastructural evidence suggests an impairment of the sensory hair cells of the cochlea following salicylate treatment. In addition, since these drugs can cause vasoconstriction, the ototoxicity of salicylates may also involve an impairment of the blood circulation in inner ear. However, a vascular hypothesis of salicylate toxicity has not received much attention. In the current study, we simultaneously measured cochlear blood flow (by laser Doppler flowmetry) and the sound-evoked potentials from the round window. Sodium salicylate caused a decrease in cochlear blood flow that appeared within 30 min following an intramuscular injection of a low dose of sodium salicylate (100 mg/kg). This sodium salicylate dose did not cause a change in auditory sensitivity. For higher doses (200 mg/kg and 300 mg/kg), both cochlear blood flow and auditory sensitivity were affected. The 300 mg/kg dose decreased blood flow by about 25% and elevated compound action potential thresholds by 10 to 25 dB for high frequencies (> or = 8 kHz). Further experiments showed that salicylate-induced threshold shifts were significantly reduced for the mid-frequencies when cochlear blood flow is increased by the vasodilating drug hydralazine (negating the flow reduction caused by salicylate). These data indicate that in addition to the direct effect of systemically administered salicylate on neurosecretory function a decreased blood flow contributes to the ototoxicity of salicylates.

Action Potentials↗
PubMed1990

Measurement of acoustic distortion reveals underlying similarities between human and rodent mechanical responses.

The level of 2f1-f2 acoustic distortion product (ADP) measured in the meatus during two-tone stimulation was compared with N 1 thresholds measured at the round window for the guinea pig. A significant inverse relation was found between distortion level and N 1 threshold. A similar relationship has also been reported for ADP level and subjective thresholds in half the human ears measured [S.A. Gaskill and A.M. Brown, J. Acoust. Soc. Am. 88, 821-839 (1990)]. Guinea pig and human ADP levels behave similarly in response to varying stimulus parameters. The ADP levels grow to a maximum and decline with increasing stimulus separation. The decline is steeper in the human ear. In both species, ADP growth as a function of stimulus level is approximately 1 with covaried stimuli; more gradual with the level of f2 (L 2) alone increasing and steeper when the level of f1 (L 1) alone is increased. The latter slopes are strongly influenced by the level of the stationary L 2 and are less steep in the human ear. A link has been proposed between differences in ADP behavior and differences in auditory filter bandwidth in the two species. Guinea pigs show little intersubject variability in ADP level. They do not show the fine structure in distortion level across frequency or the variation in growth rate seen in human responses. Differences in organ of Corti fine structure may underly these differences.

Animals↗
PubMed1997

Blood flow-independent accumulation of cisplatin in the guinea pig cochlea.

Considerable interindividual variability in the ototoxic effect of cisplatin has become the unpredictable dose-limiting factor in its use as curative as well as palliative therapy. The drug accumulates in highly vascular areas in the cochlea, causing dose-related hair cell loss. The purpose of this study was to assess blood flow-dependent aspects of cisplatin absorption in the cochlea in order to better understand factors that may influence cisplatin-induced ototoxicity. The effect of reduced cochlear blood flow on the ototoxic action of cisplatin was studied in guinea pigs. Before cisplatin administration the cochlear vasculature in each animal was unilaterally pre-constricted, by the application of 2% epinephrine to the round window. A 20-30% reduction in cochlear blood flow, assessed by laser Doppler flowmetry, was maintained before and after intravenous infusion of 0.1% cisplatin. Cisplatin infusion affected cochlear blood flow but not vessel conductivity. The cochlear blood flow decrease, maintained by local epinephrine application to the round window during cisplatin infusion, did not alter the cisplatin-induced hearing loss. In addition, the concentration of free cisplatin in scala tympani perilymph did not differ between epinephrine-treated and non-treated ears. Our results indicate that cisplatin transport into the cochlea is not an energy-dependent process in the lateral wall vasculature.

Animals↗
PubMed1997

[Diagnosis and management of Mondini malformation].

Owing to the development of imaging technology and audiology, some of the sensorineural hearing loss cases that were previcusly considered to be of unknown cause have been found to be inner ear malformation. Five cases of Mondini malformation are reviewed in this paper. CSF otorhinorrhea occurred in four cases, Klippel-Feil syndrome in three, and concurrent otosclerosis in one patient. In discussion, the authors point out that: 1) CT scanning is an supplement to audiologic tests for such patients; 2) perilymph fistula in Mondini malformation is often found at the oval window and its vicinity, the foot plate and the round window; 3) the fistula can be treated by plugging with fascial tissue via tympanoplastic approach with endaural incision. The mucosa around the fistula should be stripped away and the plugging tissue should be of dumb-bell shape.

Adolescent↗
PubMed1978

Round window membrane rupture.

Round Window Membrane Rupture is a surgically correctable cause of sudden hearing loss and vertigo. Reported is a 19-year-old male who had proven round window membrane rupture secondary to barotrauma. Surgical exploration revealed an abnormally large round window niche and membrane, possibly predisposing him to this injury. Diagnostic and therapeutic modalities of this entity are presented.

Adult↗