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At least 127 records · Page 7Linked to original sources
PubMed1982

A note on progression of the otosclerotic focus.

One thousand and thirteen consecutive patients in South Australia with stapedial fixation from otosclerosis were classified by duration of deafness, age at onset and degree of footplate pathology to determine whether there is an orderly progression in severity of the oval window lesion with duration of symptoms. The conclusions drawn were as follows. (1) An early age of onset of clinical otosclerosis, during the period of skeletal growth, dramatically increases the chance of contracting a fulminating lesion with severe and diffuse involvement of the stapedial footplate or obliteration of the oval window niche. (2) A late age of onset of clinical otosclerosis tends to be associated with lesions of the stapes footplate that are limited to the anterior pole, and there is good evidence that the lesion tends to remain stable or to progress only very slowly. (3) The case for a regular and orderly pathological progression of the otosclerotic lesion through various patterns of severity from minor to major degrees of footplate pathology is not established by the data; nor is it convincingly refuted. It is clear that if a pathological progression of the lesion does take place it must be at vastly different rates for different individuals.

Adolescent↗
PubMed2004

Fluid volume displacement at the oval and round windows with air and bone conduction stimulation.

The fluids in the cochlea are normally considered incompressible, and the fluid volume displacement of the oval window (OW) and the round window (RW) should be equal and of opposite phase. However, other channels, such as the cochlear and vestibular aqueducts, may affect the fluid flow. To test if the OW and RW fluid flows are equal and of opposite phase, the volume displacement was assessed by multiple point measurement at the windows with a laser Doppler vibrometer. This was done during air conduction (AC) stimulation in seven fresh human temporal bones, and with bone conduction (BC) stimulation in eight temporal bones and one human cadaver head. With AC stimulation, the average volume displacement of the two windows is within 3 dB, and the phase difference is close to 180 degrees for the frequency range 0.1 to 10 kHz. With BC stimulation, the average volume displacement difference between the two windows is greater: below 2 kHz, the volume displacement at the RW is 5 to 15 dB greater than at the OW and above 2 kHz more fluid is displaced at the OW. With BC stimulation, lesions at the OW caused only minor changes of the fluid flow at the RW.

Acoustic Stimulation↗
PubMed1978

Some observations on cochlear mechanics.

A set of experiments was conducted using the Mössbauer effect to determine the vibratory characteristics of the basilar membrane, Reissner's membrane, the malleus, incus, and oval window in squirrel monkey. A few measurements were also made in guinea pig in the basal cochlear region. The nonlinear vibration properties of the basilar membrane are described in detail for the midfrequency region in the squirrel monkey. Only in this region have nonlinear effects been observed. A comparison of mechanical and neural data indicates good qualitative agreement.

Animals↗
PubMed1984

High-frequency rolloff in a cochlear model without critical-layer resonance.

Zwislocki's original cochlear model, incorporating axial fluid inertia and shunt basilar-membrane stiffness and viscous resistance, possesses an operating regime not previously emphasized in the literature. Even in the absence of basilar-membrane mass and the consequent critical-layer resonance, this regime provides extraordinarily steep high-frequency rolloff. That rolloff is not associated with a critical frequency at which energy flow velocity goes to zero, but is attributable instead to a combination of two effects; (1) frequency-dependent energy coupling to the basilar-membrane viscous resistance, leading to local attenuation of the traveling wave at a rate (Np/cycle) that is directly proportional to frequency, and (2) wavelength that decreases with increasing frequency, thus increasing the number of cycles per unit length of basilar membrane. This combination leads to local attenuation of the traveling-wave amplitude (hence energy absorption from the traveling wave) that is strongly dependent on frequency, the rate (Np/cm) being proportional to the square of frequency in the long-wave mode. In Ranke's (two-dimensional, short-wave mode) version of the model, the same operating regime leads to attenuation that is even more intensely dependent on frequency, the rate being proportional to the cube of frequency.

Basilar Membrane↗
PubMed1986

"Otoacoustic" emissions in a nonlinear cochlear hardware model with feedback.

Spontaneous, simultaneous evoked as well as delayed evoked emissions are studied in a hardware model of peripheral preprocessing with nonlinear feedback. The results suggest many very close parallels to the data found for otoacoustic emissions in man. From these parallels and the additional data measurable only in the model, it can be concluded that: the cochlea acts in a similar way as established in the model; the three kinds of emissions stem from the same source; the phase response of the cochlea's hydromechanics is responsible for the frequency distance between neighboring emissions as well as for the additional tips in suppression tuning curves; the long delay of the delayed evoked emissions is due to the many decaying contributions from the places along the basilar membrane which cancel each other in the early part but sum up to the delayed emission in the later part; and the double-peaked shape of the suppression-period patterns produced by high-level, low-frequency tones reflects the symmetrically shaped saturating nonlinearity of the feedback loops in the model which correspond to the function of the outer hair cells.

Acoustics↗
PubMed1995

A spectral network model of pitch perception.

A model of pitch perception, called the spatial pitch network or SPINET model, is developed and analyzed. The model neurally instantiates ideas from the spectral pitch modeling literature and joins them to basic neural network signal processing designs to stimulate a broader range of perceptual pitch data than previous spectral models. The components of the model are interpreted as peripheral mechanical and neural processing stages, which are capable of being incorporated into a larger network architecture for separating multiple sound sources in the environment. The core of the new model transforms a spectral representation of an acoustic source into a spatial distribution of pitch strengths. The SPINET model uses a weighted "harmonic sieve" whereby the strength of activation of a given pitch depends upon a weighted sum of narrow regions around the harmonics of the nominal pitch value, and higher harmonics contribute less to a pitch than lower ones. Suitably chosen harmonic weighting functions enable computer simulations of pitch perception data involving mistuned components, shifted harmonics, and various types of continuous spectra including rippled noise. It is shown how the weighting functions produce the dominance region, how they lead to octave shifts of pitch in response to ambiguous stimuli, and how they lead to a pitch region in response to the octave-spaced Shepard tone complexes and Deutsch tritones without the use of attentional mechanisms to limit pitch choices. An on-center off-surround network in the model helps to produce noise suppression, partial masking, and edge pitch. Finally, it is shown how peripheral filtering and short-term energy measurements produce a model pitch estimate that is sensitive to certain component phase relationships.

Cochlea↗
PubMedDate not supplied

A new stapedotomy prosthesis: preliminary report.

Our study describes a newly designed stapedotomy prosthesis which consists of two components: (1) a platinum ribbon, and (2) a Teflon shaft. The first innovation is a flattened 'tab' on the posterior aspect of the platinum ribbon. The second innovation concerns the dual diameter cylinder-like shaft. Our prosthesis was implanted into 25 individuals, who underwent stapedotomy for stapes fixation, and the results are shown and discussed. Our innovations offer a proper and safe insertion of the prosthesis into the oval window associated with excellent manipulation and handling. At the same time, maximum visualization of the surgical field is achieved, while the stepped-down design of the shaft prevents the prosthesis protruding into the vestibule.

Adult↗
PubMedDate not supplied

Long-term results of a new stapedotomy prosthesis.

The long-term results of a new, home-made stapedotomy prosthesis are presented. The innovations of this prosthesis concern both portions, design for attachment to the incus and shaft. Our series include a total number of 42 individuals with stapes fixation, operated using the new prosthesis, with a medical follow-up period between eighteen months and five years. Our innovations offer a proper and safe insertion of the prosthesis into the oval window associated with excellent manipulation and handling. These advantages could be of major importance for younger surgeons and trainees. Postoperative hearing results are similar to those achieved with other commercially available pistons.

Adult↗
PubMedDate not supplied

Cochlear orientation and dimensions of the facial recess in cochlear implantation.

OBJECTIVE: To study the dimensions of the facial recess and the spatial relationship between the facial recess and the cochlea, using CT scanning in cochlear implantees. METHOD: In 29 cochlear implantees, preoperative CT scans of the temporal bone were compared with findings done at surgery. The dimensions of the facial recess and the relationship between the facial recess and the cochlea were both measured on a viewing station and classified on printed films by 3 blinded and independent reviewers. RESULTS: No significant relations could be found between either intuitive classification of facial recess width or electrode array insertion feasibility and the measurements with the viewing station. The 3 reviewers had large interobserver variability. In 5 cases, neither intuitive review of the CT scans nor viewing station measurements could predict any of the problems encountered during surgery. CONCLUSION: Our findings show that intuitive review was not reliable in classifying facial recess width. Viewing station measurements, in classifying the spatial relation between the facial recess and the cochlear basal turn, need a more detailed review in terms of the relationship with the operation direction and the orientation of the basal turn of the cochlea. Advanced imaging techniques, specifically multislice CT, might improve the diagnostic capabilities.

Chorda Tympani Nerve↗
PubMedDate not supplied

Morphometric and ultrastructural findings on human vestibular ganglion cells.

Eight human temporal bones (4 patients) were fixed within 2 h after death by perilymphatic perfusion through the oval and round windows. After preparation, 30-micron-thick sections were cut for light microscopy and ultrathin sections for ultrastructural evaluation. Under the light microscope, the diameter, the circumference and the area of the vestibular ganglion cells were measured. The data were statistically analyzed. The histograms of cell measurements showed two maxima. When observing the diameter of cells, one was at 40 microns and the other at 28 microns. Under the light microscope, we could distinguish two cell types, which mainly differed in size and content of granules in the cytoplasm. Ultrastructurally we identified also two cell types: larger cells with many mitochondria, dark clusters of endoplasmic reticulum and a varying amount of dark-stained lysosomes in the cytoplasm and smaller cells with only few mitochondria, no lysosomes and an extended rough endoplasmic reticulum. None of the ultrastructurally analyzed ganglion cells were myelinated.

Cell Nucleus↗
PubMed2003

Otosclerosis and chronic tinnitus.

Chronic subjective tinnitus is a common feature of clinical otosclerosis. Analysis of the records of 1,014 consecutive cases of clinical otosclerosis, all confirmed by stapes surgery in South Australia between 1960 and 1972, gives a preoperative prevalence of this symptom of 65%. The association of tinnitus with various predictors is considered, and a statistical analysis is presented. Tinnitus has an association with gender (p < .0001), mean preoperative bone conduction (BC) level (p = .0012), mean air conduction (AC) level (p = .0192), and mean air-bone gap (p = .0075). The associations between tinnitus and the age of the patient, the duration of deafness, the presence of Schwartze's sign, and the severity of footplate pathological involvement were all nonsignificant. The association of tinnitus with the AC and BC thresholds is unexpectedly paradoxical. An economic predictive model for tinnitus in otosclerosis has been constructed from the 2 strongly significant variables, gender and mean BC hearing level, by logistic regression. In this large series of cases, the log odds in favor of finding tinnitus are about 0.810 for male subjects and 1.394 for female subjects when the BC level is zero. The log odds fall by 0.014 for each decibel of mean BC rise.

Adolescent↗
PubMedDate not supplied

Microfissure in the oval window area.

Examination of 331 human temporal bones revealed the presence of microfissure in the oval window area in 25%. The youngest temporal bone in which the microfissure was observed was from a child eight years old and the oldest temporal bone was from an individual 102 years old. It appears that hte microfissure in this area occurs extremely rarely before 10 years of age, that it begins to be observed after the age of 10, and that the incidence of this fissure increases sharply at about age 40. In 61% of the bones in which the microfissure was observed, it was present both superior and inferior to the oval window in almost the same vertical plane. In none of the bones, however, did it extend beyond the annular ligament to the footplate. The histological appearance of the microfissure in this area was quite similar to that of the microfissure between the posterior canal ampulla and round window niche, although the latter appeared to be wider in general. The histogenesis of the microfissure is still unknown, but upon careful analysis of the results of this study and literature review, the authors consider nontraumatic spontaneous fracture by mechanical stress to be the most probable explanation for its occurrence. Possible clinical significance of the microfissure is also discussed.

Adolescent↗
PubMedDate not supplied

Perilymph fistula: the Stanford experience.

Seventy-eight tympanotomies were performed to determine the presence of perilymph fistulas (PLFs); of these, 51% were found. The oval and round windows of all patients were grafted, whether PLFs were present or not. Of those patients with PLFs, 64% had resolution of their major symptom; when no PLF was found, 44% had a similar outcome. We concluded that 1) PLFs often behave as if they are epiphenomena in relation to hearing and balance, 2) PLFs can be intermittent, 3) PLF surgery is disappointing for restoration of hearing in sudden hearing loss when compared to the rate of spontaneous recovery, 4) stabilizing a fluctuating or progressive loss is a more realistic goal, and 5) establishing preoperative criteria for exploration is still a problem.

Adolescent↗
PubMedDate not supplied

The case for small fenestra stapedectomy.

Eight hundred stapedectomies were analyzed to evaluate the long-term results with four prostheses. It was concluded that limitation of fenestra size played a most important part in the outcome of stapedectomy, especially in regard to the preservation of high-frequency bone conduction response over prolonged periods. Other advantages deriving from small fenestra stapedectomy included significantly fewer fistulae and severe sensorineural losses.

Fistula↗
PubMedDate not supplied

Microfibrillar collagen in the oval window.

Compressed microfibrillar collagen was used to seal openings in cat oval windows. Histologic examination showed the material was well tolerated and produced a good oval window seal. Because of its hemostatic properties, this material should prove to be useful when bleeding is encountered during a stapedectomy.

Animals↗
PubMed1984

Stapedectomy revision following sensorineural hearing loss.

This study analyzes 71 stapedectomies that resulted in a sensorineural hearing loss, followed by a revision stapedectomy on the suspicion of an oval window fistula. The cases were divided between two primary stapedectomy techniques: a stainless steel Robinson prosthesis on a vein graft and a wire prosthesis with Gelfoam. The major differences between the surgical findings of the two groups were the fistula rate with the wire prosthesis was 10 times that with the Robinson prosthesis; the wire prosthesis was longer than necessary in 21% of the cases in which it was used; there was no finding of excess length with the Robinson prosthesis; and after revision stapedectomy, dizziness was lessened in 20% of the patients in the Robinson prosthesis group, in 60% of those in the wire prosthesis group, and in 75% of those with fistula. Surgical directions are given for revision stapedectomy following a sensorineural hearing loss.

Cochlear Implants↗