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At least 361 records · Page 20Linked to original sources
PubMed1998

Kinetics of gentamicin uptake in the inner ear of Chinchilla langier after middle-ear administration in a sustained-release vehicle.

The search for a safe, effective treatment for the vertigo associated with Meniere's disease has long been an important topic in otolaryngology. In recent years many groups have begun using intratympanic gentamicin to treat this vertigo. Although reported cure rates are as high as 90%, many questions remain regarding this type of treatment. Current limitations are the necessity for repeated treatments and a lack of clear dosing guidelines. In addition, the gentamicin must be delivered in a manner that allows maximal vestibulotoxic effect without injury to hearing. Until investigators can control the exact amount of medicine that is placed in the ear and have an understanding of the kinetics of gentamicin absorption, adequate dosing guidelines will be difficult to establish, and therapy will continue to rely on empiric data. We describe the use of a fibrin-based sustained-release vehicle, impregnated with gentamicin, injected into the middle ear of chinchillas. This allows for a prolonged effect without repeated dosing. Using this model, we studied the absorption kinetics of gentamicin at time points ranging from 8 hours to 1 week after injection. We used our findings to create a kinetics curve of gentamicin absorption. We discuss the shape and characteristics of this kinetics curve and examine the effects of the fibrin-based sustained-release vehicle and gentamicin on the middle ear. We noted no absorption in the contralateral (untreated ear) or blood. Through better understanding of the actions of gentamicin in this animal model, we hope to facilitate safer use of intratympanic medicines in our patient population and initiate programs for the use of this sustained-release vehicle in human beings.

Animals↗
PubMed1985

Experimental investigation of temperature gradients in the inner ear following argon laser exposure.

In microsurgery of the middle ear using argon laser, heat is produced on the sensorineural structures adjacent to the irradiated bones. Thermal gradients following laser applications have been measured by means of special thermocouples. The footplate was perforated by a 50 msec. ray applied both at 380 mWatt and at 460 mWatt. The maximum temperature increase registered in the labyrinthine spaces was respectively 2 degrees C. and 3.5 degrees C. Coagulation of the promontory mucosa was performed using 100 msec. impulses at 200 mWatt. At the end of a series of 12 applications the temperature increase at the level of the basal coil was 1.4 degrees C. From the above results the authors conclude that no damage is induced during laser microsurgery and that, considering the power and time values relative to impulses, the use of laser in routine clinical practice should be relatively safe.

Ear, Inner↗
PubMedDate not supplied

Bilateral deafness in a maltese terrier and a great pyrenean puppy: inner ear morphology.

Two puppies, a 4-month-old female Maltese terrier and a 6-week-old male Great Pyrenean, were presented for confirmation of bilateral deafness by electrophysiological testing. In both puppies, brainstem auditory potentials were not evoked by 90 dB NHL click stimulation of each ear. Examination of the inner ear revealed a bilateral cochleo-saccular degeneration in both animals. The lesions were characterized by generalized atrophy of the stria vascularis, collapse of the cochlear duct, degeneration of the organ of Corti, an abnormal tectorial membrane, and saccular collapse, with a normal spiral ganglion. The cochlear duct was entirely obliterated throughout the cochleae in the Maltese terrier puppy, but was locally and asymmetrically affected in the Great Pyrenean. The abnormalities observed in the Maltese terrier puppy were identical with those previously described in deaf Dalmatian puppies; the lesions observed in the Great Pyrenean, however, were less typical. This is the first histopathological description of cochleo-saccular degeneration in the Maltese terrier and Great Pyrenean breeds. In both puppies the defect was probably congenital.

Animals↗
PubMed2002

The roles of the external, middle, and inner ears in determining the bandwidth of hearing.

The view seems to prevail that the frequency range of hearing is determined by the properties of the outer and middle ears. We argue that this view is an oversimplification, in part because the reactive component of cochlear input impedance, which affects the low-frequency sensitivity of the cochlea, is neglected. Further, we use comparisons of audiograms and transfer functions for stapes (or columella) velocity or pressure in scala vestibuli near the stapes footplate to show that the middle ear by itself is not responsible for limiting high-frequency hearing in the few species for which such comparisons are possible. Finally, we propose that the tonotopic organization of the cochlea plays a crucial role in setting the frequency limits of cochlear sensitivity and hence in determining the bandwidth of hearing.

Animals↗
PubMed2002

Three-dimensional Fourier transformation constructive interference in steady state magnetic resonance imaging of the inner ear in patients with unilateral and bilateral Menière's disease.

OBJECTIVE: In this study, three-dimensional Fourier transformation constructive interference in steady state (3DFT-CISS) magnetic resonance imaging was used to quantify the distance between the vertical part of the posterior semicircular canal and the posterior fossa as a measure of the endolymphatic sac and duct in patients with Menière's disease. Differences in this distance between affected and unaffected ears, as well as differences between unilaterally and bilaterally affected patients, were studied and compared with a control group. Also, possible correlations between the measured distance and the duration and severity of symptoms, patient age, and average hearing loss were investigated in the group of patients with Menière's disease. STUDY DESIGN: Retrospective clinical study. SETTING: Tertiary referral center (University Hospital) as part of a large, diagnostic research project on Menière's disease. PATIENTS: Of the 111 patients with Menière's disease initially included, 90 patients underwent 3DFT-CISS MRI. Eighty-six of these patients were analyzed in this MRI study. Fifty-six patients had unilateral Menière's disease, and 30 patients had bilateral Menière's disease (116 affected and 56 unaffected ears). Sixty-two ears in patients without Menière's disease were studied as controls. INTERVENTION: The distance between the vertical part of the posterior semicircular canal and the posterior fossa was determined by 3DFT-CISS MRI. MAIN OUTCOME MEASURES: Contiguous axial 3DFT-CISS MRI slices of 0.7 to 1.0 mm were made by a radiologist according to a strict protocol. Measurements of the distance between the vertical part of the posterior semicircular canal and the posterior fossa were taken by two professionals-a radiologist and an otolaryngologist-using a ruler and the original scan. RESULTS: A significantly smaller distance (2.9 mm) between the vertical part of the posterior semicircular canal and the posterior fossa as visualized on MRI scans was found in the ears of patients with Menière's disease than in the ears of patients in the control group (3.8 mm, p < 0.001). In both uni- and bilaterally affected patients (n = 56 and n = 30, respectively), no significant difference between ears was found (p = 0.44 and p = 0.19, respectively). In bilaterally affected patients, however, this distance (3.2 mm) was significantly greater than the distance in unilaterally affected patients (2.7 mm, p = 0.004). There was no relationship between the MRI-visualized distance between the vertical part of the posterior semicircular canal and the posterior fossa and the duration of disease, average hearing loss, or severity of symptoms in uni- and bilaterally affected patients. CONCLUSION: The difference in MRI-visualized distances between the vertical part of the posterior semicircular canal and the posterior fossa of uni- and bilaterally affected patients strongly suggests that unilateral and bilateral hearing loss are two different entities in patients with Menière's disease. The size of the endolymphatic sac seems not to be the only factor in the pathogenesis of Menière's disease. That the MRI-visualized distance between the vertical part of the posterior semicircular canal and the posterior fossa does not have any relationship to the duration of the disease or to patient age indicates that this distance is a congenital feature.

Ear, Inner↗
PubMed1988

Inner ear surgery.

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Ear Diseases↗
PubMedDate not supplied

Inner ear hemorrhage and endolymphatic hydrops in a leukemic patient with sudden hearing loss.

Several significant histopathological findings were noted in a case of sudden hearing loss in a patient with chronic lymphocytic leukemia. The major pathological findings were leukemic hemorrhage into both perilymphatic and endolymphatic spaces in the cochlear and vestibular systems, endolymphatic hydrops in the cochlea and sacculus, and a relatively narrowed and straightened vestibular aqueduct and endolymphatic sac. Additional interesting findings include: loss of hair cells in the organ of Corti and vestibular end-organs; destruction of the stria vascularis (possibly the origin of the blood); fibrosis in the perilymphatic spaces in the cochlea and the vestibule, and in the endolymphatic space in the vestibule; and new bone formation in the perilymphatic spaces in the vestibule. The leukemic infiltrate observed in both the cochlea and the vestibule was not considered to be significant. Hemorrhage into the cochlea is thought to be the most reasonable cause of the sudden hearing loss in this case. Also discussed are fibrosis and osteogenesis as a late consequence of hemorrhage, and the coexistence of endolymphatic hydrops with an anomaly of the vestibular aqueduct and endolymphatic sac.

Aged↗