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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↗
PubMed1998

Enlarged cochlear aqueduct.

Enlargement of the cochlear aqueduct is a controversial topic, with experienced investigators doubting its existence because of a lack of published cases. We describe the CT appearance of an enlarged cochlear aqueduct in a patient with advanced congenital inner ear anomalies and congenital hearing loss. The intent of this article is to present the CT appearance of a presumably enlarged cochlear aqueduct and to underscore the need to examine this structure in patients with congenital hearing loss.

Cochlear Aqueduct↗
PubMed1997

The cochlear aqueduct in pediatric temporal bones.

The cochlear aqueduct is a bony channel which contains the fibrous periotic duct and connects the perilymphatic space of the basal turn of the cochlea with the subarachnoid space of the posterior cranial cavity. Previous histological studies suggested that patency depended on age, whereas a more recent study showed no statistical correlation between age and patency. To clarify patency in pediatric cochlear aqueducts, we selected 21 temporal bones from 12 infants and children, varying in age from birth to 9 years, in which the cochlear aqueduct was fully visible on one histological section. Photographs were taken for documentation and the length and width of the orifice of the external aperture of the aqueduct at the scala tympani were measured and followed to the internal aperture at the subarachnoid space. The lumen of the duct was examined for mononucleated cells, blood cells and fibrous tissue. Measurements revealed that the mean length of the cochlear aqueduct was 4.6 mm (range, 2.4-10.7 mm), mean width of the external aperture was 484 microm (range, 225-869 microm), and mean width of the internal aperture was 1293 microm (range, 699-2344 microm). The mean diameter of the narrowest part (isthmus) was 151 microm (range, 75-244 microm). In all temporal bones the cochlear aqueduct was patent, with one exception. This latter temporal bone was from a 2-month-old girl with multiple intralabyrinthine anomalies, with the missing cochlear aqueduct believed to be due to an aplasia. Our results support prior measurements of the cochlear aqueduct and demonstrate a short and patent cochlear aqueduct in newborns. With growth, a significant increasing length of the duct was found.

Aging↗
PubMed2004

Direct measurement flow resistance of cochlear aqueduct in guinea pigs.

OBJECTIVE: The cochlear aqueduct connects the scala tympani to the subarachnoid space and is the main pressure equalization canal for the inner ear. Increases in inner ear volume and pressure are thought to cause clinical symptoms such as vertigo, tinnitus and fluctuating hearing loss. In this study the flow resistance of the cochlear aqueduct was determined and its relation with inner ear pressure was studied. MATERIAL AND METHODS: Inner ear pressure was measured in the scala tympani through the round window using a micropipette. Through a second micropipette, artificial perilymph was infused into, or withdrawn from, the scala tympani at various constant rates. From the infusion rate and the change in perilymphatic pressure during infusion the flow resistance of the cochlear aqueduct was calculated. RESULTS: The flow resistance was found not to be constant but to depend on the position of the round window membrane and possibly on the magnitude and direction of fluid flow through the aqueduct. Measured flow resistance values were in the range 11-45 Pa s/nl. For very small flow values the flow resistance averaged over 6 animals was 21 Pa s/nl. CONCLUSIONS: The flow resistance of the cochlear aqueduct is not a constant value. The cochlear aqueduct is a canal with dynamic properties and may play a role in the complicated process of inner ear pressure regulation.

Animals↗
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↗
PubMed1999

New aspects in the histopathology of the cochlear aqueduct in children.

OBJECTIVE: To study the histoanatomy and pattern of growth of the cochlear aqueduct in children of different ages. BACKGROUND: Since Du Verney described the cochlear aqueduct in 1684, its form, pattern of growth, patency, and function have been controversial. As most of the previous studies of the aqueduct were performed on adults, none had looked at its pattern of growth from the neonate to 9 years of age. In addition, previous histologic studies had suggested an age-dependent patency, but recent investigations had not statistically correlated patency with age. METHOD: Histologic sections of 137 temporal bones from 79 infants and children were studied by light microscopy. From this group, we selected 32 temporal bones from 18 infants, newborn to 9 years (average age 9.1 months, median 0.5 months), in whom the entire length of the cochlear aqueduct was visible on one histologic section. We measured the width of the orifices at the scala tympani (external aperture) and the subarachnoid space (internal aperture) and the length of the aqueduct, and noted the contents of the lumen. RESULTS: The measurements of the cochlear aqueduct were: length 4.19 mm (range 1.7-10.7 mm), width of the external aperture 435 microm (range 225-869 microm), width of the internal aperture 1,323 microm (range 699-2344 microm), mean diameter of the narrowest part (isthmus) 138 microm (range 68-244 microm), intraluminal mononucleated cells 6%, and erythrocytes 15%. CONCLUSIONS: Our findings demonstrate that, in the newborn, the cochlear aqueduct is short and patent. After birth, the duct lengthens significantly primarily by growth of the medial periosteal portion. There was no statistically significant change in the diameter of the external and internal apertures and the isthmus with age. With one exception, the cochlear aqueduct was always present and patent.

Adult↗
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↗
PubMed2001

Relationship of the cochlear aqueduct and inner ear pressure in Ménière's disease and in a normal population.

OBJECTIVE: The aim of this study was to determine the dimensions of cochlear aqueduct radiologically in patients with Ménière's disease and in normal subjects, and to correlate these findings with normal and low static acoustic compliance (SAC) (high and normal perilymphatic pressure) to see whether the dimensions of the cochlear aqueduct play any role in the perilymphatic pressure in normal individuals and patients with Ménière's disease. STUDY DESIGN: Prospective double-blind study. SETTING: The study was conducted at Hacettepe University Medical Faculty, a tertiary care center. PATIENTS: Forty patients with Ménière's disease with bilateral involvement, diagnosed by vertigo attacks, fluctuating hearing loss, tinnitus, fullness in the ear, and cochlear sensitivity constituted the patient group. Forty healthy individuals with no otolaryngologic symptoms constituted the control group. INTERVENTIONS: All individuals underwent SAC measurement in terms of equivalent volume in milliliters, based on two volume measurements. To measure the dimensions of the cochlear aqueduct, high-resolution computed tomography of the temporal bone in the axial plane was performed. RESULTS: There was no statistically significant difference in the width of the cochlear aqueduct between patients with Ménière's disease and normal subjects. When SAC measurements were also taken into account, there was no difference in cochlear aqueduct dimensions between individuals with normal and low SAC values in the two groups. CONCLUSION: The dimensions of cochlear aqueduct are not significantly different in Méniére's disease patients and normal individuals. Also, the cochlear aqueduct does not appear to play a significant role in normal and low SAC values in the two groups of individuals.

Adolescent↗
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↗
PubMed1994

Perilymph pressure during hypobaric conditions--cochlear aqueduct obstructed.

Nine cats with the cochlear aqueduct surgically blocked were anaesthetised, put in a pressure chamber, and stepwise exposed to hypobaric pressure, each of the two steps lasting 5 min. The chamber pressure was reduced to -5 and -7 kPa. Concluding the experiment the cats were observed for 5 min after restoration of atmospheric pressure. The perilymph, tympanic cavity, cerebrospinal fluid, central venous, arterial and surrounding chamber pressures were continuously recorded. Reduced chamber pressure caused relative overpressure within the tympanic cavity, thereby inducing pressure gradients between the chamber, the tympanic cavity, the labyrinth and the cerebrospinal fluid and vascular pressures respectively. Our results demonstrate that hypobaric effects on the labyrinth are mediated via pressure changes in the tympanic cavity and not by systemic, vascular or cerebrospinal fluid influence. Substantial perilymph overpressure lasted throughout the hypobaric conditions. The magnitude and the duration of this overpressure were influenced by the patency of the Eustachian tube whereas the rate of the pressure change in the chamber was of little importance. As atmospheric pressure was restored in the chamber the overpressure in the labyrinth was reversed to underpressure--relative to pre-experimental conditions.

Animals↗
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↗