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Results for “Cochlear Aqueduct”

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At least 145 records · Page 8Linked to original sources

PubMed2000

Temporal bone findings in multiple endocrine neoplasia type 2B.

To our knowledge, present case is the first published report of temporal bone findings in multiple endocrine neoplasia type 2B (MEN-2B). We describe a 43-year-old Japanese man with medullary thyroid carcinoma (MTC), pheochromocytoma, mucosal neuroma and a Marfanoid body habitus. The collateral adrenal tumors and MTC were removed surgically. However, 14 years after surgery, the MTC and pheochromocytoma recurred and the patient died of intracranial hemorrhage due to hypertension. During the autopsy, metastatic MTC was detected in the liver, lungs, kidneys, pancreas and cervical lymph nodes. Recurrent pheochromocytoma was present in the right kidney. Mucosal neuromas were found in the tongue, gastrointestinal tract and vesical nerve plexus. The following histopathological findings were seen in both temporal bones: metastatic MTC was found as well as neuromas and the cochlear aqueduct was widely patent.

Adult↗

PubMed1989

Scanning electron microscopic studies of the capillaries crossing the scala tympani.

Scanning electron microscopic examinations were carried out on the perilymphatic space bordering the round window in guinea pigs. A number of small vessels were found crossing free through the lumen of the scala tympani in this area. The larger number (5-10) of these capillaries are suspended between the bony cochlear wall and the terminal net of fibrocytes which covers the cochlear opening of the cochlear aqueduct and spreads onto the basal third of the round window membrane. Other capillaries (3-5) cross the lumen of the scala tympani from the outer cochlear wall to the modiolus. All of these capillaries have a thin endothelium and a very thin pericytic covering. These findings suggest that the capillaries crossing the perilymphatic space may give rise to a different chemical composition of the perilymph bordering the round window in comparison with the more upper parts of the scala tympani.

Animals↗

PubMed2002

Change of guinea pig inner ear pressure by square wave middle ear cavity pressure variation.

The inner ear fluid pressure of guinea pigs was measured during square wave middle ear cavity pressure variation. Time constants were derived for the slopes of the inner ear pressure recovery curves after middle ear pressure change. A "single exponential" function did not fit well and therefore more complicated functions were used for this purpose. For middle ear pressure increasing from zero to a few centimetres of water, returning to zero again, decreasing from zero to minus a few centimetres of water and then returning to zero again, time constants for the inner ear pressure recovery curves were on average 15.0, 8.6, 2.5 and 2.5 s, respectively. The results could not be described using a linear model with constant window membrane compliance and cochlear aqueduct flow resistance. A possible explanation for the large difference in time constants for positive or negative middle ear pressure changes is a dependence on aqueduct flow resistance or round window membrane position.

Animals↗

PubMedDate not supplied

Perilymph production and cochlear blood flow.

In rodents at least, the main sources of the perilymph fluid are (1) influx of CSF through the cochlear aqueduct, and (2) blood flow dependent local production within the cochlea. Experimental data are presented that give a ratio of 22:78 percent for those sources. The perilymph production thus derives mainly from the cochlear blood flow. It is concluded that measurements of the perilymph production can be used as indirect measurements of the inner ear blood flow under various experimental conditions. Two experimental examples are referred to.

Acidosis, Respiratory↗

PubMedDate not supplied

Three-dimensional reconstruction of the cochlea from two-dimensional images of optical sections.

This paper describes a methodology for three-dimensional (3D) computer-aided reconstruction of the guinea pig cochlea using orthogonal-plane fluorescence optical sectioning. Specimens are sectioned optically, allowing them to remain intact during observation. Equations to correct the data for specimen translation and rotation are developed and 3D reconstructions of the scala tympani, round window membrane, and cochlear aqueduct are presented. The error associated with the reconstruction is estimated to be < 19 microns.

Animals↗

PubMed1999

Persistent bilateral hearing loss after shunt placement for hydrocephalus. Case report.

Transient hearing decrease following loss of cerebrospinal fluid (CSF) has been reported in patients undergoing lumbar puncture, spinal anesthesia, myelography, and/or different neurosurgical interventions. The authors present the first well-documented case of a patient with persistent bilateral low-frequency sensorineural hearing loss after shunt placement for hydrocephalus and discuss the possible pathophysiological mechanisms including the role of the cochlear aqueduct. These findings challenge the opinion that hearing decreases after loss of CSF are always transient. The authors provide a suggestion for treatment.

Audiometry, Pure-Tone↗

PubMedDate not supplied

Perilymphatic communication routes in the auditory and vestibular system.

Horseradish peroxidase was injected into the foramen magnum and oval window of guinea pigs to determine perilymphatic communication routes and boundaries. The primary route to the auditory system appeared to be through the cochlear aqueduct. Perineural spaces of the eighth nerve contributed to this communication and provided the principal perilymphatic communication routes to the vestibular system. Light and electron microscopic examination were used to identify membrane permeability and define boundaries in the epithelial lining of the auditory and vestibular endorgans.

Animals↗

PubMedDate not supplied

Congenital cerebrospinal otorrhea.

Four locations for congenital cerebrospinal fluid fistula in the region of a normal labyrinth are reviewed. A congenital leak may occur through the petromastoid canal, a wide cochlear aqueduct, Hyrtl's fissure, or the facial canal. A fistula through the initial segment of the fallopian canal was successfully repaired in a two-year-old boy who had three episodes of meningitis following otitis media. Knowledge of these four sites of congenital defects provides a guideline for the surgeon in the identification and repair of cerebrospinal fluid leaks in the region of the labyrinth.

Cerebrospinal Fluid Otorrhea↗

PubMed2000

Transduction of the contralateral ear after adenovirus-mediated cochlear gene transfer.

Cochlear gene transfer is a promising new approach for inner ear therapy. Previous studies have demonstrated hair cell protection with cochlear gene transfer not only in the inoculated, but also in the uninoculated ear. To characterize the kinetics of viral spread, we investigated the extent of transgene expression in the contralateral (uninoculated) cochlea after unilateral adenoviral cochlear gene transfer. We used a lacZ reporter gene vector, and demonstrated spread of the adenovirus into the cerebrospinal fluid (CSF) after cochlear inoculation of 25 microl viral vector. Direct virus application into the CSF resulted in transduction of both cochleae, whereas virus inoculation into the bloodstream did not. The cochlear aqueduct was identified as the most likely route of virus spread to the contralateral cochlea. These data enhance our understanding of the kinetics of virus-mediated transgene expression in the inner ear, and assist in the development of clinical applications for inner ear gene therapy. Our results showed a functional communication between the CSF and the perilymphatic space of the inner ear, that is not only of importance for otological gene transfer, but also for CNS gene transfer. Gene Therapy (2000) 7, 377-383.

Adenoviridae↗

PubMed1983

Relationships of labyrinthine fluid pressures and blood flow.

Control of labyrinthine blood flow analogous to the autoregulation of cerebral blood flow has been suggested but not experimentally demonstrated. This study concerns the influence of systemic arterial pressure changes on the perilymph and CSF pressures in cats with the cochlear aqueduct (CA) blocked. No direct correlation was found between changes in arterial and CSF pressure. This seemed to be due to the efficient autoregulation of the global cerebral blood flow--a main factor for CSF pressure regulation. The CSF and central venous pressures induced little and much delayed influence on the perilymph pressure when the CA was blocked. However, there was a direct correlation between changes in systemic arterial pressure and the perilymph pressure. This relationship seemed to be mediated via changes in local labyrinthine blood flow. The study indicated a lack of autoregulation of labyrinthine blood flow and a direct correlation between labyrinthine fluid pressure and blood flow when the CA was obstructed.

Animals↗

PubMed1996

[Noninvasive determination of pressure relations of intracranial and intracochlear fluid spaces during the glycerol test in normal probands and patients with Menière's disease].

BACKGROUND: The cochlear aqueduct is a route for direct pressure transfer between intracranial and intracochlear fluids. In patients with Menière's disease, intracochlear pressure is presumably disturbed. The "Tympanic Membrane Displacement Analyser (TDA)" is a new system which provides a useful noninvasive method of detecting intracranial and intracochlear pressure changes. PATIENTS: In this study TDA measurements in combination with a glycerol test were performed in nine patients with Menière's disease and in seven normal persons. RESULTS: Before ingestion of glycerol, no significant difference in pressure was found between the two groups. After ingestion of glycerol a temporary decrease in intracochlear pressure was detected in both groups without any significant difference between the two groups. CONCLUSION: These results show that the combination of glycerol testing and TDA measurements does not seem to be helpful for the differential diagnosis of Menière's disease.

Adult↗

PubMed1992

Pressure transfer between the perilymph and the cerebrospinal fluid compartments in cats.

This is a review of our studies of the labyrinthine fluid pressure in cats subjected to pressure changes in the middle ear (implosive routes) and the cerebrospinal fluid compartment (explosive routes) as well as to changes in vascular and ambient pressures. The perilymph, cerebrospinal fluid (CSF), middle ear, venous and arterial pressures were measured with the cochlear aqueduct (CA) patent as well as surgically blocked. Experiments on explosive pressure changes revealed that the perilymph pressure was regulated by the CSF in case of CA patency. The CSF influence was dominant enough to obscure any direct effect on the labyrinth from other sources. With the CA obstructed the CSF influence on the labyrinth was apparently mainly via the endolymphatic sac and duct although limited and much delayed. Systemic arterial pressure changes had a pronounced influence on the perilymph pressure, but this effect was revealed only when the CSF influence was reduced by CA obstruction. Experiments on implosive and ambient pressure changes suggested that there was no fundamental difference in the perilymph response to equivalent levels of implosive versus hypobaric pressure. Three factors determined the effect of implosive and hypobaric pressure: the patency of the CA, the rate of the pressure change, and the eustachian tube function.

Air Pressure↗

PubMed1997

Tympanic membrane displacement analysis after glycerol intake: effects on intracranial and intracochlear fluid pressure.

BACKGROUND: Intracranial pressure is transmitted to the perilymph of the cochlea via the cochlear aqueduct and to the endolymph via Reissner's membrane. The tympanic membrane displacement analyzer (TDA) is a new system that may provide a useful, noninvasive, indirect method to identify intracranial and intracochlear pressure changes. METHODS: We performed measurements in 20 persons with normal hearing and in 29 patients with various unilateral diseases of the inner ear such as sudden hearing loss or Meniere's disease. Another series of measurements were done in 15 normal-hearing persons and in 15 patients with Meniere's disease before and after oral ingestion of glycerol. RESULTS: In the first series of measurements, no significant differences in the tympanic membrane displacement were found between normal-hearing individuals and patients with unilateral diseases of the inner ear. In the second series, in all individuals a temporary, relative decrease in intracochlear pressure was found after oral ingestion of glycerol but without any significant difference between the two groups. CONCLUSIONS: These results revealed that the TDA is apparently not useful in the evaluation of patients having Meniere's disease.

Acoustic Impedance Tests↗

PubMed1996

High-resolution T2-weighted MR imaging of the inner ear using a long echo-train-length 3D fast spin-echo sequence.

The purpose of this study was to assess the value of a long echo-train-length 3D fast spin-echo (3D-FSE) sequence in visualizing the inner ear structures. Ten normal ears and 50 patient ears were imaged on a 1.5T MR unit using a head coil. Axial high-resolution T2-weighted images of the inner ear and the internal auditory canal (IAC) were obtained in 15 min. In normal ears the reliability of the visualization for the inner ear structures was evaluated on original images and the targeted maximum intensity projection (MIP) images of the labyrinth. In ten normal ears, 3D surface display (3D) images were also created and compared with MIP images. On the original images the cochlear aqueduct, the vessels in the vicinity of the IAC, and more than three branches of the cranial nerves were visualized in the IAC in all the ears. The visibility of the endolympathic duct was 80%. On the MIP images the visibility of the three semicircular canals, anterior and posterior ampulla, and of more than two turns of the cochlea was 100%. The MIP images and 3D images were almost comparable. The visibility of the endolymphatic duct was 80% in normal ears and 0% in the affected ears of the patients with Meniere's disease (p < 0.01). In one patient ear a small intracanalicular tumor was depicted clearly. In conclusion, the long echo train length T2-weighted 3D-FSE sequence enables the detailed visualization of the tiny structures of the inner ear and the IAC within a clinically acceptable scan time. Furthermore, obtaining a high contrast between the soft/bony tissue and the cerebrospinal/endolymph/ perilymph fluid would be of significant value in the diagnosis of the pathologic conditions around the labyrinth and the IAC.

Adult↗

PubMed2001

Dynamics of inner ear pressure change caused by intracranial pressure manipulation in the guinea pig.

Previous studies have shown that pressure changes in the cerebrospinal fluid compartment are transmitted to the inner ear. The main route for pressure transfer is the cochlear aqueduct. about which little is known with regard to its dynamic properties. In the present study, sudden intracranial pressure changes (square waves and short pulses) were created in guinea pigs by means of an electronically controlled infusion system. Simultaneously with pressure manipulation, hydrostatic pressure was monitored in both the peridural space and the perilymphatic compartment of the inner ear. The onset of an inner ear pressure change following manipulation of intracranial pressure was immediate. Inner ear pressure increased or decreased without a measurable time lag, and equalized within a few seconds. During square wave intracranial pressure manipulation, inner ear pressure equalized somewhat more slowly after pressure increase than after pressure decrease. To a first approximation, the pressure equalization curves for the inner ear could be fitted with a single exponential function, rising or falling with a time constant in the range 1-3 s, and the system can be described as a low-pass filter composed of a constant compliance and a constant flow resistance. Detailed analysis, however, showed small deviations from a purely exponential recovery process. With a more complicated (non-linear) model, almost perfect fits to the inner ear pressure equalization curves could be obtained. This non-linearity may be a consequence of the dependence of the compliance and, or flow resistance on pressure.

Animals↗

PubMed2000

Postural-induced changes in intracranial pressure evaluated non-invasively using the MMS-10 tympanic displacement analyser in healthy volunteers.

Inner ear pressure reflects intracranial pressure (ICP) primarily because of the direct communication of perilymph and cerebrospinal fluid (CSF) through the cochlear aqueduct (CA). The MMS-10 tympanic displacement analyser (TDA) is a relatively new device for measuring perilymphatic pressure non-invasively, and thereby also indirectly measuring intracranial pressure. The aim of the present study was to evaluate the use of the TDA in a daily clinical setting. Other aims were to investigate changes in perilymphatic pressure from sitting to lying position in healthy volunteers in two age groups (mean age: 33 years and 50 years) and to compare the patency of the CA in these groups using the MMS-10 TDA. Tympanic membrane displacement (TMD) analyses were performed in the test subjects initially twice in sitting position (test-retest) and then in sitting and supine positions. We found that the MMS-10 TDA is easy to use, and that it gives reproducible values in repeated tests, but with large inter-subject differences. The TMD test showed curves, which, in the whole test group, were more negative in supine position, in accordance with an increasing intracranial and inner ear pressure when lying down. The change from sitting to lying position was larger in the younger group than in the older group. In 11% of the younger group (males) and in 30% of the older group (females), the CA was considered to be non-patent, although the difference was not statistically significant. However, the finding is in keeping with the hypothesis of a greater proportion of patent CA in younger than in older individuals.

Adult↗

PubMed1989

Correlation of high resolution computed tomography and gross anatomic sections of the temporal bone. Part III. Cochlear and vestibular aqueducts.

Gross anatomic sections of isolated temporal bones (TB) were compared with high resolution computed tomography (CT) scans obtained utilizing contiguous 1.5-mm thick slices in the transaxial, coronal, and sagittal planes. Each TB was then sectioned at 2.0-mm intervals in planes parallel to those of the CT scans. Both the cochlear and vestibular aqueducts were best visualized in the coronal plane; the transaxial plane proved less reliable and the sagittal plane was not useful at all. The cochlear aqueduct in the coronal plane appears as a funnel-shaped configuration with its widest portion opening into the subarachnoid space. The vestibular aqueduct at its opening into the epidural space is well visualized in the coronal plane, and as it traverses the bone toward the vestibule it appears as an oval to spherical lucency, whereas in transaxial sections it is seen as a small longitudinal lucency.

Cochlea↗

PubMed2003

High-resolution T1-weighted 3D real IR imaging of the temporal bone using triple-dose contrast material.

The small structures in the temporal bone are surrounded by bone and air. The objectives of this study were (a) to compare contrast-enhanced T1-weighted images acquired by fast spin-echo-based three-dimensional real inversion recovery (3D rIR) against those acquired by gradient echo-based 3D SPGR in the visualization of the enhancement of small structures in the temporal bone, and (b) to determine whether either 3D rIR or 3D SPGR is useful for visualizing enhancement of the cochlear lymph fluid. Seven healthy men (age range 27-46 years) volunteered to participate in this study. All MR imaging was performed using a dedicated bilateral quadrature surface phased-array coil for temporal bone imaging at 1.5 T (Visart EX, Toshiba, Tokyo, Japan). The 3D rIR images (TR/TE/TI: 1800 ms/10 ms/500 ms) and flow-compensated 3D SPGR images (TR/TE/FA: 23 ms/10 ms/25 degrees) were obtained with a reconstructed voxel size of 0.6 x 0.7 x 0.8 mm3. Images were acquired before and 1, 90, 180, and 270 min after the administration of triple-dose Gd-DTPA-BMA (0.3 mmol/kg). In post-contrast MR images, the degree of enhancement of the cochlear aqueduct, endolymphatic sac, subarcuate artery, geniculate ganglion of the facial nerve, and cochlear lymph fluid space was assessed by two radiologists. The degree of enhancement was scored as follows: 0 (no enhancement); 1 (slight enhancement); 2 (intermediate between 1 and 3); and 3 (enhancement similar to that of vessels). Enhancement scores for the endolymphatic sac, subarcuate artery, and geniculate ganglion were higher in 3D rIR than in 3D SPGR. Washout of enhancement in the endolymphatic sac appeared to be delayed compared with that in the subarcuate artery, suggesting that the enhancement in the endolymphatic sac may have been due in part to non-vascular tissue enhancement. Enhancement of the cochlear lymph space was not observed in any of the subjects in 3D rIR and 3D SPGR. The 3D rIR sequence may be more sensitive than the 3D SPGR sequence in visualizing the enhancement of small structures in the temporal bone; however, enhancement of the cochlear fluid space could not be visualized even with 3D rIR, triple-dose contrast, and dedicated coils at 1.5 T.

Adult↗