PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Cochlear Aqueduct”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1984

Radiographic classification of the vestibular and cochlear aqueducts: the paired correlation between normal and abnormal vestibular aqueduct and cochlear aqueduct anatomy.

Multidirectional tomography (MDT) can be useful in determining the caliber, shape, and course of the vestibular aqueduct (VA) and cochlear aqueduct (CA). Clinical decisions have been based on the findings from MDT. Unfortunately, the clinical utility of these observations has been confusing and controversial because similar MDT techniques were not used. This study will address some of the difficult questions and clinical controversies derived from MDT observations. This new perspective has evolved with the use of high resolution computed tomography (HRCT). An analysis of 750 petrous bones for the occurrence of the various types of VAs and CAs using Gado's classification, further vestibular aqueduct and a variation of Gado's classification for the cochlear classification is reported. The distribution of the possible paired types of VA and CA are evaluated. MDT results indicate that the paired analysis in patients with inner ear dysfunction is not useful, cost effective, diagnostic, or of prognostic value. MDT can provide clinically valid observations of periaqueductal and perilabyrinthine pneumatization which is helpful in anticipating the size and position of the endolymphatic sac at the time of surgery for those few patients who may benefit from endolymphatic system surgery. However, when a comparison is made between MDT and CT of 60 ears in those same patients, the clinical limitations of MDT for inner ear diagnosis and prognosis became apparent. The future for HRCT scanning with reformatting holds potential for clinically meaningful visualization of inner and middle ear structures previously expected from MDT imaging.

Cochlea↗
PubMedDate not supplied

Patency of the cochlear aqueduct.

The patency of the cochlear aqueduct is discussed against the background of radioanatomic studies of 225 plastic casts of temporal bone specimens and additional experimental and clinical observations. The occasional presence of a wide venous channel running parallel with the cochlear aqueduct, as well as the existence of up to three accompanying venous channels can simulate a pathologically wide cochlear aqueduct radiographically. This could constitute a diagnostic pitfall in the absence of other clinical and radiographic signs of malformation.

Adolescent↗
PubMed1989

[Cochlear aqueduct].

The morphology and structure within the cochlear aqueduct have been investigated on the basis of a histological analysis of 234 temporal bones ranging from 12-week old to adult. Barrier membrane was found in 28.6% of the temporal bones examined, and fibrous reticular tissues of the inner opening of the cochlear aqueduct in 38.1% of the temporal bones. No any tissue in the inner opening of the cochlear aqueduct was seen in 33.3%. Periotic duct was filled with loose reticular tissue. The clinical significance of contents in the cochlear aqueduct was discussed.

Adult↗
PubMedDate not supplied

Anatomic variations of the human cochlear aqueduct. A radioanatomic investigation.

The cochlear aqueduct follows a course through the petrous pyramid that varies from straight and steeply vertical to a curvilinear and horizontal. Its course and length are correlated to the pneumatization of the pyramid and also to the volume of the jugular fossa. These two factors influence the radiographic reproduction of the cochlear aqueduct, especially in computed tomography in the axial transverse projection but to a far lesser degree in multidirectional tomography.

Cochlea↗
PubMedDate not supplied

Effects of hypobaric pressure on the labyrinth. Cochlear aqueduct patent.

Cats with the cochlear aqueduct patent were placed in a pressure chamber and exposed for 10 min to hypobaric pressures of 5.1 and 6.8 kPa relative to atmospheric pressure. The experiments were designed according to a program used for treatment of Meniere's disease. The perilymph, middle ear, cerebrospinal fluid (CSF), venous, arterial and chamber pressures were recorded. The results demonstrated that hypobaric effects on the labyrinth were mediated via pressure changes in the middle ear and not via a systemic vascular or CSF influence. A reduction in chamber pressure induced a relative increase in middle ear pressure. It was the rate of the hypobaric change as well as the patency of the cochlear aqueduct and the Eustachian tube function that determined the magnitude of the initial perilymph peak pressure and the duration of this pressure increase. A rapid versus a slow rate induced an initial perilymph increase of 3.4 and 2.2 kPa, respectively. This relative pressure increase was eliminated within 1 min via the patent aqueduct. Thus, neither did a longstanding perilymph pressure increase occur during the hypobaric exposure, nor did a prolonged significant reduction in perilymph pressure occur after atmospheric pressure was restored.

Animals↗
PubMedDate not supplied

Obliteration of vestibular and cochlear aqueducts in animals.

The right vestibular aqueduct was obliterated in guinea pigs, chinchillas, and monkeys, and the right cochlear aqueduct and both the right vestibular and right cochlear aqueducts were obliterated in guinea pigs and chinchilas. Changes in auditory acuity were monitored by determining averaged temporal-response thresholds, and temporal-bone histologic studies were performed. Obliteration of the vestibular aqueduct or both the vestibular and cochlear aqueducts consistently produced endolymphatic hydrops in guinea pigs. In these animals, the auditory acuity gradually deteriorated. The low tones consistently were depressed more than the high tones. The auditory changes corresponded to the severity of endolymphatic hydrops. On the other hand, no significant histologic or audiometric changes were demonstrated in monkeys after obliteration of the vestibular aqueduct or in chinchillas after obliteration of the vestibular aqueduct or of both the vestibular and cochlear aqueducts. No significant histologic or audiometric changes were demonstrated in guinea pigs and chinchillas after obliteration of the cochlear aqueduct.

Animals↗
PubMedDate not supplied

The surgical approach to the endolymphatic sac and the cochlear aqueduct in the guinea pig.

The endolymphatic sac and cochlear aqueduct are primary passages of the endolymphatic and perilymphatic fluid compartments in the labyrinth. Closure of the endolymphatic sac and duct in the guinea pig will result in the development of endolymphatic hydrops. Although obstruction of the cochlear aqueduct in this species does not seem to result in any dysfunction, this structure may serve in the dynamics of inner ear fluid physiology. The anatomy of the guinea pig temporal bone is described with special emphasis on the endolymphatic sac and cochlear aqueduct. Surgical techniques to gain access to these structures through both a middle and posterior cranial fossa approach are described.

Animals↗
PubMedDate not supplied

High-resolution computed tomographic appearance of normal cochlear aqueduct.

Computed tomographic (CT) scans of 37 patients with normal adult cochlear aqueducts were selected for retrospective analysis. Usually, only the inferomedial part of the cochlear aqueduct could be seen on axial CT. The sizes of the external cochlear aqueduct opening were tabulated, and they did not vary significantly with age or gender. The average width was 2.9 mm. Of the configurations found, the most common was the funnel (22 cases).

Adolescent↗
PubMedDate not supplied

Studies on cochlear aqueduct patency.

Complex studies on the patency of the cochlear aqueduct were made on 250 human cadavers and the temporal bones isolated from these, using a chemical method (staining reaction) as well as filling the aqueduct with fluid plastics and exposing the whole of its course under an operating microscope. The disappearance of patency in the cochlear aqueduct is a progressive phenomenon reflecting the biological process of aging in the organism. Patency of the cochlear aqueduct renders possible a two-way spread of infection from the cerebrospinal fluid (CSF) to the inner ear and vice versa, CSF otorrhea, and sudden sensorineural hearing inpairment through rises in CSF pressure, while in the absence of patency, the accumulation of harmful products of metabolism in the perilymph has a deleterious effect on the sensory elements of the inner ear.

Adolescent↗
PubMed1988

Venous communications of the cochlea after acute occlusion of the vein of the cochlear aqueduct.

The vein of the cochlear aqueduct (VCAQ) is the principal drainage vein of the cochlea in the guinea pig. Morphological observations of the VCAQ and its adjacent structures were made by studying serial sections of the cochlea. We detected the presence of two collateral vessels from the mucoperiosteal veins of the middle ear which communicated with the VCAQ. Following acute occlusion of the VCAQ, marked dilatations of these vessels were observed in corrosion cast preparations. Our findings suggest that these vessels act as collateral veins following acute venous congestion of the inner ear.

Animals↗
PubMedDate not supplied

Transmission of cerebrospinal fluid pressure via the cochlear aqueduct and endolymphatic sac.

The concept of perilymphatic and endolymphatic pressure balance is generally linked to the theory that the endolymphatic sac transmits cerebrospinal fluid (CSF) pressure changes to the endolymph to equalize CSF pressure changes transmitted to the perilymph via the cochlear aqueduct. This theory, and the significance of other mechanisms of CSF pressure influence on the labyrinth, were evaluated experimentally. Continuous measurements of perilymphatic, CSF, venous, and arterial pressures were performed on cats with the cochlear aqueduct patent or obstructed and the inferior cochlear vein intact or occluded. Intracranial pressure changes were induced by subarachnoid infusion of artificial CSF in live and dead animals. With the cochlear aqueduct patent, CSF pressure changes were transmitted to the perilymph without any significant dampening or time lag. With the cochlear aqueduct obstructed, CSF pressure changes induced significantly lower and delayed changes in perilymphatic pressure. Similar results were obtained whether the animals were alive or dead and the cochlear vein intact or blocked. This indicated a passive mechanism not induced by changes in labyrinthine fluid production or blood flow. Long-standing, stable elevation of CSF pressure with the cochlear aqueduct blocked induced a slowly increasing perilymphatic pressure, always stabilizing at a pressure rise significantly less than that of CSF. The results do not suggest any major pressure transfer via perineural or perivascular routes. The endolymphatic sac is postulated to mediate a reduced and delayed transfer of increased intracranial pressure to the labyrinth.

Animals↗
PubMed1991

Ultrastructure of the guinea pig cochlear aqueduct. An electron microscopic study of decalcified temporal bones.

The ultrastructure of the guinea pig cochlear aqueduct was examined using semi-thin and thin sections. The lumen of the cochlear aqueduct was occupied by a sparse meshwork of fibroblasts and delicate connective tissue trabeculae. The periotic tissue lining the bony wall of the aqueduct was composed of multiple layers of both elongated cells and densely arranged laminae of collagen fibrils. These structures were identical to those of the dura mater and the arachnoid. The opening to the perilymphatic space of the scala tympani also contained connective tissue trabeculae, but the arrangement of fibroblasts was more compact here than in the main part of the duct. These structural features suggest that fluid can move freely through cochlear aqueduct, and that the effects of sudden pressure changes in the CSF may be protected against by the densely and perpendicularly arranged fibroblast at the opening to the perilymphatic space.

Animals↗
PubMed1988

Morphological changes in the cochlear aqueduct following herpes simplex virus inoculation into the subarachnoid space.

Type 1 herpes simplex virus (HSV-1) was inoculated into the subarachnoid space through the cisterna magna of guinea pigs to study morphological changes of the inner ear and the ability of the cochlear aqueduct to protect the inner ear. Although most of the animals developed clinical manifestations of meningoencephalitis within a few days after inoculation, Preyer's reflex remained intact. Scanning electron microscopy revealed some significant changes in the cochlear aqueduct. Lymphocytes and macrophages were predominant, with narrowing of reticular tissue spaces caused by the swelling of the periotic duct tissue. The cribriform structure of the internal orifice of the cochlear aqueduct appeared to be completely obstructed, whereas it was normal in the presence of bacterial infection as previously reported (1). The morphological changes were confined to the cochlear aqueduct.

Animals↗
PubMed1987

Fluid flow in the cochlear aqueduct and cochlea-hydrodynamic considerations in perilymph fistula, stapes gusher, and secondary endolymphatic hydrops.

There is convincing evidence that the cochlear aqueduct is normally patent in humans and is of relatively constant size. It probably plays an important role in the balance between the perilymphatic, endolymphatic, and cerebrospinal fluid pressures. The flow rate of liquids through tubes is a linear function of pressure, viscosity, and length of the tube but is a fourth degree power function of the radius of the lumen. For this reason, the radius is the most critical factor determining the flow rate. Small variations in size of the cochlear aqueduct can cause very large variations in flow rate through it.

Cochlea↗
PubMed1991

Computer-aided three-dimensional reconstruction of guinea pig cochlear aqueduct.

A computer-aided method of three-dimensional reconstruction was applied to the determination of the overall spatial configuration of the guinea pig cochlear aqueduct. The rotation function of the reconstructed images was useful in showing the individual small parts of the duct. A semi-translucent display of the segmental reconstruction of the duct demonstrated a difference in the density of the cellular components between the opening to the perilymphatic space and the duct portion. We propose that the cochlear aqueduct serves as a protective mechanism against a sudden change in CSF pressure in the subarachnoid space.

Animals↗
PubMed1984

Defense mechanism of the cochlear aqueduct against infection. A morphological study in the guinea pig.

Guinea pigs were used in this study. Physiological saline, india ink, and Staphylococcus aureus were injected into the cisterna magna, and S. aureus was also injected into the scala tympani. Changes in the microstructure of the cochlear aqueduct were observed by light microscopy and also by scanning electron microscopy, mainly by means of fracture preparations. From these experimental results, it could be confirmed that the periotic duct tissue of the cochlear aqueduct reacted especially to bacterial infection.

Animals↗
PubMedDate not supplied

Human cochlear aqueduct and its accessory canals.

The anatomy of the adult human cochlear aqueduct and its surrounding structures, and their normal variations at tomography, microdissection and plastic molding are described. The mean length of the aqueduct is 12.9 mm and the mean width of its funnel-shaped external aperture 4.2 mm. The mean width of the narrowest portion is 0.14 mm. No difference in aqueductal width was found between the youngest and oldest age groups. Complete bony obstruction was revealed at microdissection in 3 out of 82 specimens. In the remaining 79 the entire aqueduct was patent. The aqueduct usually runs parallel to the internal auditory canal when seen from above, and the AP projection is therefore most suitable for tomography. At tomography the entire aqueduct was visualized in 60% of the specimens. The isthmic portion was not visible in 40%. Major reasons for nonvisualization of the entire aqueduct are: 1) a luminal width less than 0.1 mm, 2) a high jugular fossa, 3) a posteriorly directed aqueductal convexity (10%), and 4) bony obliteration (4)%). Accessory canals close to and often wider than the aqueduct may complicate tomographic evaluation of the aqueductal patency. Nonvisualization of the aqueduct at tomography does not necessarily indicate nonpatency.

Adult↗