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PubMedDate not supplied

Cochlear hair cell loss in ears with cholesteatomas. Scanning electron microscopy study.

Cochleas from 16 Mongolian gerbils with spontaneous aural cholesteatomas, and four of similar age without cholesteatomas, were examined by scanning electron microscopy to quantify cochlear hair cell loss. Loss of hair cell stereocilia was found in all ears with cholesteatomas and was significantly increased when compared with uninvolved ears from animals of similar age. The hair cell loss associated with gerbilline cholesteatomas appeared to be most marked in the middle turn of the cochlea and increased in severity with increasing size of the cholesteatomas. Outer hair cells were affected more than inner hair cells. Inner and outer hair cell loss was not significantly different in infected cholesteatomas versus sterile cholesteatomas. The greater damage to hair cells at the middle turn compared to the basal turn suggests that these losses may be the result of some agent acting through the cochlear wall rather than through the round window.

Animals↗
PubMed1989

Implantation of the Melbourne/Cochlear multiple-electrode extracochlear prosthesis.

The Melbourne/Cochlear multiple-electrode extracochlear implant is designed for deaf patients who are unsuited to multiple-electrode intracochlear implantation. The implant consists of a receiver-stimulator package connected via a lead wire assembly to six individual stimulating electrodes. There is a choice of two alternative surgical procedures, both of which are via a combined middle ear approach using anterior and posterior tympanotomies. Four active electrodes shaped into compressible platinum-iridium soft-balls are fed through the mastoid cavity and across the facial recess, and placed into cavities that are made over the cochlear turns that project to the medial wall of the middle ear. One hard-ball active electrode is placed into the round window niche. One hard-ball reference electrode is placed into the hypotympanum. An additional electrode wrapped around the lead wire assembly can be used as an alternative reference electrode. A specially designed insertion needle facilitates the placement and the fixation of the soft-ball electrodes.

Cochlear Implants↗
PubMed1995

Correlation of beta-2 transferrin and middle ear abnormalities in congenital perilymphatic fistula.

Congenital perilymphatic fistula (PLF) as a diagnosis for progressive, fluctuating, or sudden sensorineural hearing loss with or without vertigo is still controversial. Beta-2 transferrin is a protein that is unique to cerebrospinal fluid, aqueous humor, and perilymph. A recent pilot study demonstrated that beta-2 transferrin may be an objective test to determine the existence of a congenital PLF. The authors prospectively evaluated and recommended surgery for 43 children with suspected PLF over the past 3 years. A prospective, blinded study was performed by having the attending otolaryngologist evaluate the middle ear at the time of surgery for a PLF and any middle ear abnormalities. Samples of fluid were collected from the oval and round windows and were tested for beta-2 transferrin. Of 16 patients undergoing tympanoplasty or tympanomastoidectomy who served as controls, none were positive for beta-2 transferrin. Of the 43 patients undergoing exploratory tympanoplasty for PLF, 20 (46.5%) were considered to be negative for PLF on microscopic visualization; 23 (53.5%) were found to be positive. Of the 20 patients thought to be negative for PLF, 18 (90%) tested negative for beta-2, but 2 of these patients were positive for beta-2, and both had a congenital middle ear abnormality. Of the 23 patients found to have a PLF at surgery, 6 (26.1%) tested positive for beta-2, and all of these 6 had middle ear abnormalities. Of the 17 patients negative for beta-2, 9 had normal anatomy; 6 had middle ear abnormalities, and 2 had erosive changes. The authors conclude that beta-2 transferrin, an objective test, confirms the existence of congenital PLF in children, which is associated with middle ear abnormalities.

Adolescent↗
PubMedDate not supplied

Surgical treatment of Meniere's disease.

Results are reported of the effect ov various surgical methods on vertigo in Meniere's disease. Minor preocedures like sacculotomy or application of NaCl crystals in the round window may effect a cure, but often results in deaf ears. Vestibular nerve section seems to offer the best of vertigo, while generally still preserving residual hearing.

Adult↗
PubMed2004

[Combined middle and inner ear abnormality: report of a case].

Congenital anomalies of the middle ear associated to anomalies of the inner ear are rarely described. Our case displays a malformation due to an association of congenital absence of the round window and aplasia of the semi-circular canals, causing conductive hearing loss. First diagnosis was a congenital atresia isolated of the round window, related to a previous surgical exploration. We tried a novel technique designed to restore the function of the round window. Labyrinthine anomalies prevented a good outcome. This kind of malformative association could be due to the complexity of early genetic control of ear development. Attentive analysis of imaging should be performed before middle ear surgery to determine the presence of inner ear anomalies which are quite frequent and which would limit its usefulness.

Abnormalities, Multiple↗
PubMed1975

Experimental aural barotrauma. Electrophysiological and morphological findings.

The electrophysiological findings show a time and pressure related decrease in function of the CM and the N1 potentials. Sudden changes were correlated with tympanic membrane perforations. Some of the decreased function is accounted for by middle ear effusion and hemorrhages, reducing mechanically the transmission of sound energy through the middle ear. This was evidenced by an improvement of function when the fluids were removed. Remaining decreases in function were interpreted as a result of influences on the inner ear function or of undisclosed middle ear changes. No differences were noted in cochlear function between animals subjected to sustained or intermittent middle ear pressures. Neither were any morphological differences noted between these two groups in the middle or inner ear. The morphological middle ear findings correlated well with previous clinically and experimentally induced changes with increased/decreased middle ear pressure. The cochlear findings include the interesting observation of an intact round window membrane, a clear endolymph, and a normal Organ of Corti in all cases. Positive findings were a high frequency of hemorrhage, most commonly demonstrated in the scala tympani of the basal turn close to the round window. The origin of the hemorrhages could not be demonstrated with the present investigation. The hemorrhages often appeared to be related to the cochlear aqueduct. The occurrence of hemorrhage was clearly related to increased negative pressure, and the non-existence of hemorrhage was always related to either tympanic membrane perforations or low applied pressure. Further frequent findings were distention, collapse, and rupture of the inner ear membranes which must be interpreted with great circumspection due to the method used. Likewise, some of the pathological cochlear findings may be due to pathological conditions which are not necessarily related to induced middle ear pressure.

Acoustic Stimulation↗
PubMed1982

Electrically induced potentiation of eighth nerve responses.

Whole-nerve potentials were recorded from a total of 42 anesthetized cats using a 25-micron electrode in the 8th nerve as it exits from the internal auditory meatus, in response to acoustic clicks across an 80-db range. Biphasic electric pulses, 0.5 msec in duration, 100/sec for 5-10 min, at 100 microamps, were delivered by the 8th nerve electrode. Potentiation of responses to acoustic clicks was observed in amplitude, latency, and duration when comparing sets of pre- vs post-stimulation output. High consistency was achieved. These data were corroborated by recording output also from the round window, and by auditorily evoked brainstem far field potentials with a subcutaneous electrode. Control experiments such as ablation of AI, AII, EP, and IT, resection of the inferior colliculus, the crossed olivocochlear bundle, and middle-ear muscles, determined that electric potentiation was a local effect. Furthermore, the usual electric pulses applied to an electrode on the round window had no potentiating effect. Electric stimulation had a significant effect at the .001 level in increasing amplitude of response. Latency of N1 was shortened by 0.2 msec. Potentiation persisted for up to 3 hrs. An unexpected result was potentiation of 8th nerve and brainstem nuclei responses after acoustic stimulation of the contralateral ear; electric stimulation may induce a more active involvement of efferent activity originating in the superior olive or more rostrally. The interpretation of how such changes might affect perception after, for example, long term stimulation of neurons by a prosthesis is difficult to make without behavioral corroboration. The amplitude change of the whole-nerve action potentials are rough indicators of relative loudness. Thus an accentuated loudness may be experienced over time as equivalent intensities tend, as in these cats, to elicit greater response. The long time constancy of the decay, on the other hand, could tend to maintain a consistency of such potentiated responses and thus create no real variability in perception over time. The shortened latency could mean an involvement of higher frequency perception, but how this might be translated into a change in, for example, intelligibility of speech it is not possible to infer at this time.

Acoustic Stimulation↗
PubMed2000

Electrocochleography in the diagnosis of Meniere's disease.

This study prospectively analyses electrocochleography (ECoG) recordings obtained from ears demonstrating symptoms highly suggestive of Meniere's disease. Comparison is made with ECoG recording from ears in which the diagnosis of Meniere's is considered unlikely (control ears). Electrocochleograph recordings were made through a transtympanic recording needle, situated in the round window niche. Analysis was made of the 1 kHz tone burst summation potential (SP) and the summation potential:action potential (SP/AP) ratio response to a 90 dB click. All patients were prospectively awarded a Meniere's score based on a 10-point scale, and comparison was made between ears awarded a score of 7 or greater (Meniere's ears; n > 500), and ears awarded a score 3 or less (control ears; n > 900). Results demonstrate a significant difference in the 1 kHz SP response, and the SP/AP ratio, between "control" and "Meniere's" ears. Furthermore, we show that SP negativity is proportional to the amplitude of the AP click response, and in patients producing an AP click amplitude exceeding 10 V, sensitivity of the tone burst test approaches 85%. This study provides further evidence suggesting the useful role of electrocochleography in determining a diagnosis of endolymphatic hydrops. and demonstrates improved sensitivity of the 1 kHz SP response, compared with SP/AP click ratio, in the diagnosis of Meniere's disease.

Action Potentials↗
PubMed1995

Persistent dizziness following head trauma and perilymphatic fistula.

A growing body of evidence supports the idea that dizziness that persists for months and even years can be caused by an unsuspected perilymphatic fistula. Perilymphatic fistulas are abnormal ruptures that allow perilymph to leak out of the inner ear into the middle ear space. Most commonly, these ruptures occur secondary to a traumatic event. The term postconcussive syndrome has been used to describe a myriad of symptoms following head trauma. Some of these symptoms, such as cognitive changes, tinnitus, neck stiffness, and dizziness, are also commonly caused by active perilymphatic fistulas. This article discusses the typical history and diagnostic tests for patients with perilymphatic fistula. Common diagnostic tests include audiograms, electronystagmograms, electrocochleograms, and subjective and platform fistula tests. Also, the surgical treatment for the perilymphatic fistula (ie, repair of the oval and round windows) is reviewed, along with the results produced by this relatively minor ear operation. Suggestions are made to help the medical professionals involved in rehabilitative care to be aware of perilymphatic fistulas and seek proper consultations from inner ear specialists if they suspect the existence of this easily cured disorder.

Adult↗
PubMed2006

In vivo imaging of mammalian cochlear blood flow using fluorescence microendoscopy.

AIMS: We sought to develop techniques for visualizing cochlear blood flow in live mammalian subjects using fluorescence microendoscopy. BACKGROUND: Inner ear microcirculation appears to be intimately involved in cochlear function. Blood velocity measurements suggest that intense sounds can alter cochlear blood flow. Disruption of cochlear blood flow may be a significant cause of hearing impairment, including sudden sensorineural hearing loss. However, inability to image cochlear blood flow in a nondestructive manner has limited investigation of the role of inner ear microcirculation in hearing function. Present techniques for imaging cochlear microcirculation using intravital light microscopy involve extensive perturbations to cochlear structure, precluding application in human patients. The few previous endoscopy studies of the cochlea have suffered from optical resolution insufficient for visualizing cochlear microvasculature. Fluorescence microendoscopy is an emerging minimally invasive imaging modality that provides micron-scale resolution in tissues inaccessible to light microscopy. In this article, we describe the use of fluorescence microendoscopy in live guinea pigs to image capillary blood flow and movements of individual red blood cells within the basal turn of the cochlea. METHODS: We anesthetized eight adult guinea pigs and accessed the inner ear through the mastoid bulla. After intravenous injection of fluorescein dye, we made a limited cochleostomy and introduced a compound doublet gradient refractive index endoscope probe 1 mm in diameter into the inner ear. We then imaged cochlear blood flow within individual vessels in an epifluorescence configuration using one-photon fluorescence microendoscopy. RESULTS: We observed single red blood cells passing through individual capillaries in several cochlear structures, including the round window membrane, spiral ligament, osseous spiral lamina, and basilar membrane. Blood flow velocities within inner ear capillaries varied widely, with observed speeds reaching up to approximately 500 microm/s. CONCLUSION: Fluorescence microendoscopy permits visualization of cochlear microcirculation with micron-scale optical resolution and determination of blood flow velocities through analysis of video sequences.

Animals↗
PubMed2003

Imaging of congenital middle ear deafness.

INTRODUCTION: Conductive hearing loss, in the presence of a normal external ear, is usually due to an interference with the normal transmission of sound from the tympanic membrane across the ossicular chain to the oval window. If conductive hearing loss occurs in a young child, congenital middle ear pathology is the most likely cause. MATERIALS AND METHODS: High resolution computed tomography of the middle ear is the diagnostic modality of choice. Details of the imaging technique are outlined in this article. Eight cases of congenital middle ear deafness imaged in the radiological departments of Changi General Hospital and Tan Tock Seng Hospital in Singapore are illustrated. RESULTS: Congenital middle ear deafness may be classified into ossicular chain abnormalities, congenital ossicular fixation, congenital oval window atresia and congenital round window atresia. The imaging features for each category are described. CONCLUSION: With proper imaging technique and a systemic analysis of the images, the abnormalities that result in congenital middle ear deafness can usually be demonstrated on most occasions.

Deafness↗
PubMed1997

Evidence that inner hair cells are the major source of cochlear summating potentials.

The role of the inner hair cells (IHCs) in generating the cochlear summating potentials (SP) was assessed by measuring SP, cochlear nerve action potentials (CAP), cochlear microphonics (CM) and 2f1-f2 distortion product otoacoustic emissions (DPOAEs) in 15 chinchillas with either acute chemical de-afferentation, accomplished by applying kainic acid to the round window, or surgical de-afferentation and basal IHC loss, which developed within two months after sectioning the auditory nerve. In the auditory nerve sectioned ears, type I ganglion cells disappeared whereas most, if not all, type II ganglion cells were still present. Histological analysis of surface preparations and sections through the modiolus verified the de-afferentation in both models and showed a large IHC loss at the base of the cochlea in the ears with the auditory nerve sectioned while other structures of the cochlea remained intact. Unoperated (left) ears of 9 animals served as controls. CM and DPOAEs were normal in all ears whereas the CAP was substantially depressed in de-afferented ears. Comparisons among the SP input-output functions suggest that (1) the IHCs are the major generator of SP recorded from the round window in chinchilla, in particular at low to moderate stimulus levels, (2) the SP recorded from the round window largely reflects the responses from hair cells at the base of the cochlea, and (3) kainic acid results in an increase of SP amplitude to high-level stimuli whereas the SP to low- to moderate-level stimuli remains in the normal range.

Acoustic Stimulation↗
PubMed1980

Model for cochlear echoes and tinnitus based on an observed electrical correlate.

Experiments in cat have revealed evidence of temporal correspondence between round-window recorded electrical potentials and delayed acoustical responses in the sealed ear canal at low sound levels. This would be difficult to explain if the acoustic response contained an appreciable component of delay due to a reverse travelling wave. An alternative interpretation is offered in which outer hair cells are assumed to undergo periodic volumetric changes correlated with their electrochemical activity. These volume changes would act on, and be divided between, the oval window, giving acoustic reemission and the basilar membrane, giving a secondary travelling wave. Owing to the active nature of the hair cell, the output is potentially greater than the input, so that when the secondary travelling wave exceeds the initial one, the amplitude will build up and continuous oscillation occurs, giving 'tinnitus'.

Animals↗
PubMed1989

Selective damage to cochlear efferents by the choline neurotoxin ethylcholine mustard aziridinium ion (AF64A) in the chinchilla.

The cholinotoxin ethylcholine mustard aziridinium ion (AF64A) was diluted in artificial perilymph to concentrations ranging from 10-100 microM, injected unilaterally into the bulla of chinchillas, and allowed to passively diffuse across the round window membrane. Following 21-day survival, the animals were sacrificed and ears removed and embedded in epoxy for histological evaluation under both light and transmission electron microscopy. At 10 microM concentration, selective degeneration of efferent fibers was observed in the efferent terminals on outer hair cells (OHC), tunnel radial fibers, tunnel spiral bundle, and the inner spiral bundle. Serial sections of the middle turn of an animal at 10 microM concentrations showed normal efferent terminals on approximately 50% of OHCs. At the higher concentrations non-specific damage was seen in OHCs, afferents, and some supporting cells. These data suggest that low doses AF64A produces selective damage to cochlear efferent terminals and fibers in the chinchilla.

Animals↗
PubMed2007

Cochlear cytokine gene expression in murine acute otitis media.

OBJECTIVE: Recurrent acute otitis media (AOM) causes sensorineural hearing loss by unknown mechanisms. It is widely accepted that inflammatory cytokines diffuse across the round window membrane to exert cytotoxic effects. This study addresses whether inner ear cells are capable of expressing genes for inflammatory cytokines. STUDY DESIGN: The authors conducted a prospective animal study. METHODS: BALB/C mice underwent transtympanic injection of heat-killed Haemophilus influenzae to create an acute inflammatory response. These mice were compared with a control group in addition to a group of uninjected mice found to have otomicroscopic changes consistent with persistent or chronic otitis media. The cochleas of these mice were obtained, their RNA harvested, and cytokine gene expression analyzed using prefabricated cDNA arrays. RESULTS: Four groups of mice (control, 3-day postinjection, 7-day postinjection, and mice with chronic otitis media) with five mice in each group were analyzed. Numerous classes of genes were found to be upregulated or downregulated by more than twofold. Some genes differed from control mice by more than 10-fold. These genes included numerous fibroblast growth factors, interleukins, tumor necrosis factors, and colony-stimulating factors. CONCLUSION: The genes of numerous inflammatory cytokines are either up- or downregulated by murine inner ear cells in response to either acute or chronic inflammation of the middle ear. This study provides a novel site of production of cytokines that may be responsible for the damage seen in sensorineural hearing loss.

Acute Disease↗
PubMed1985

Temporal bone findings in a case of otopalatodigital syndrome.

The principal features of the otopalatodigital syndrome are hearing loss, cleft palate, and skeletal dysplasia of the hands and feet. The right temporal bone was acquired from a boy with this syndrome who died at the age of 2 1/2 years. Behavioral audiometry had indicated a conductive hearing loss, with probable near-normal sensorineural function; brainstem evoked response audiometry indicated a mild sensorineural hearing loss. Histologic studies of the temporal bone revealed dysmorphic features in both the middle ear and the bony labyrinth. The ossicles were deformed, the stapes was fixed, and no round window was present. A defect of the modiolus resulted in a wide communication between the subarachnoid space of the internal auditory canal and the scala vestibuli. These anomalies would clearly have frustrated any attempt to improve the patient's hearing through reconstructive middle ear surgery.

Abnormalities, Multiple↗