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↗

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↗

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↗

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Anatomic variations of the human semicircular canals. A radioanatomic investigation.

The anatomic variations of the semicircular canals were investigated in a series of 95 plastic temporal bone preparations. The results showed a wider range of variability than has been assumed previously. An intraindividual correlation was found between the sizes of the superior and lateral semicircular canals. Observations indicate why a semicircular canal is not invariably delineated on one tomographic plane despite correct positioning for its optimum reproduction.

Humans↗

PubMedDate not supplied

The topographic relations of the high jugular fossa to the inner ear. A radioanatomic investigation.

The radioanatomy of high jugular fossae and their topographic relations to the inner ear structures were investigated in 245 unselected temporal bones. One hundred and fifty specimens were submitted to multidirectional and 10 to computed tomography. After careful chemical and fermentative maceration plastic casts were made, using polyester resin and silicone rubber. With the use of vacuum, even minute structures became filled with the casting material. The specimens offered a three-dimensional view of the jugular fossae and surrounding structures. Fifty-eight (24%) of the total 245 specimens had high jugular fossae at a level above the lower border of the round window. Five casts showed a dehiscence of the peripheral portion of the vestibular aqueduct caused by the high jugular fossa. In 2 casts the proximal portion of the cochlear aqueduct was affected. In some casts the posterior semicircular canal, the facial canal, the stapedial muscle and the round window lay so close to the fossa that a dehiscence could not be excluded. In a clinical material of 102 high fossae the radiographic findings were in accordance with the experimental results. High jugular fossae were predominantly found in pyramids with low-grade mastoid bone pneumatization and sparse or no perilabyrinthine air cells.

Adolescent↗

PubMedDate not supplied

The semicircular canals of the inner ear and the pneumatization of the temporal bone. A radioanatomic investigation.

In an investigation of 94 plastic casts of temporal bone specimens a wide range of variations both in the general outline of the pyramid and in the anatomy of its specific structures was found. Attempts were made to estimate the transverse and vertical dimensions of the petrous bone. Both the mastoid and the perilabyrinthine pneumatization correlated to the dimensions of some structures, but not to the size and shape of the semicircular canals.

Humans↗

PubMedDate not supplied

Investigation of temporal bone anatomy by plastic moulding and cryomicrotomy.

To increase our understanding of the complex topographic relations between temporal bone structures and to facilitate the interpretation of their radiographic images, two techniques were developed. Plastic moulding of temporal bone specimens using polyester resin and silicone rubber substances providing detailed information and a three-dimensional survey of the structures. Carefully macerated temporal bone specimens are filled with plastic material under vacuum and the bone is then dissolved. The preparations, freed from irrelevant structures and embellished, allow metric evaluation of the different structures and their topographic relations. Automatic serial cryomicrotomy of fresh, deep-frozen temporal bones, using a commercial sledge-cryomicrotome. Photography of the cut surfaces of the specimen, usually at distance of 0.25 to 0.50 mm, allows natural-colour reproduction of minute detail, e.g. the melanin cell area in the cochlea, the smallest vessels on the ossicular surfaces, and the origin of the cochlear aqueduct at the basal turn of the cochlea. By correlating the photographs with images from the corresponding tomographic planes accurate information is obtained for interpretation of the radiographic images. A combination of the two techniques facilitates a detailed study and is a valuable aid in the teaching of temporal bone anatomy.

Freezing↗

PubMedDate not supplied

The jugular bulb diverticulum. A radioanatomic investigation.

Two hundred and forty-five temporal bone specimens were examined radiographically. Subsequently the topographic relationship between the jugular fossa and surrounding structures was evaluated in plastic casts of the specimens. Fifty-eight casts showed a high jugular fossa and in 17 a jugular bulb diverticulum was found. A diverticulum is regarded as an anomaly of the high jugular bulb and presumably has a potential for expansion. Most frequently a diverticulum was directed medially into the space between the internal acoustic meatus, the vestibular aqueduct and the posterior cranial fossa. Seven diverticula reached the level of the internal acoustic meatus. Encroachment upon the vestibular aqueduct was seen in 4 casts and both the internal acoustic meatus and the cochlear aqueduct were very close to the diverticulum. A few diverticula were directed postero-laterally close to the facial canal and the stapedius muscle. The investigation was supplemented with a selected clinical material of radiographs of temporal bones with high fossae. The results corresponded to those of the experimental investigation. The jugular bulb diverticulum is a relatively common feature and should be regarded as an anomaly with a potential to give rise to clinical symptoms consequent to its intrusion upon surrounding structures.

Bone Diseases↗

PubMedDate not supplied

Effects of a high jugular fossa and jugular bulb diverticulum on the inner ear. A clinical and radiologic investigation.

From a series of patients undergoing routine radiographic examination, 112 temporal bones with a high jugular fossa were selected. Among these, 43 jugular bulb diverticula were found. The structures affected by a high fossa or diverticulum were recorded and correlated to the clinical symptoms of the patient. The vestibule was suspected to be affected in five patients. Two of these patients had tinnitus and vertigo, and three had hearing loss. In one of the latter the hearing loss was most marked in the supine position. The cochlea was close to the fossa in three patients, all of whom had tinnitus. Four patients had a defect of the posterior semicircular canal. One of them lost his hearing after a severe fit of coughing, became unsteady and showed signs of a fistula. The internal acoustic meatus and the mastoid portion of the facial canal were affected in two and four patients, respectively, who had no recorded symptoms. Twelve of 34 patients with Menière's disease and a high jugular fossa on the side of the diseased ear had a dehiscence of the vestibular aqueduct caused by the fossa or diverticulum, compared with nine of 58 patients in the unselected material. For comparison and demonstration of topographic relationships, 58 casts of unselected radiographed temporal bone specimens with high jugular fossae or diverticula were investigated. In patients with a high jugular fossa or jugular bulb diverticulum, tomographic assessment may be of value.

Diverticulum↗

PubMedDate not supplied

The subarcuate fossa and channel. A radioanatomic investigation.

The subarcuate channel conveys the blood supply to the otic capsule of the semicircular canals, to part of the vestibule and to other neighbouring structures. It is often observed in conventional radiographs of the temporal bone and is reproduced to advantage by conventional multidirectional and computed tomography. The purpose of this report is to draw the attention of otoradiologists to this anatomic structure and to report on some results concerning the radioanatomy of the channel. Plastic casts of 100 radiographed and subsequently macerated temporal bones were evaluated. Fourteen temporal bone specimens were submitted to automatic serial cryomicrotomy. The radioanatomic variations of the channel were demonstrated. The radiographic reproducibility of the channel, length and width, were found to be dependent on the degree of perilabyrinthine and mastoid pneumatization of the temporal bone.

Female↗

PubMedDate not supplied

The vestibular aqueduct in patients with Menière's disease. A tomographic and clinical investigation.

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Adolescent↗

PubMedDate not supplied

The labyrinthine portion of the facial canal. A comparative radioanatomic investigation.

The variational radiographic anatomy of the labyrinthine portion of the facial canal was investigated in 200 plastic and silicone casts of unselected temporal bone specimens by means of multidirectional and computed tomography in different projections. The labyrinthine portion of the canal varied considerably in shape and size; in some specimens the cross-section was circular, but often the canal was crumpled and flattened in its passage above the cochlea. The medial part of the labyrinthine portion was narrowest, the lowest cross-sectional area being 0.5 mm2. In spite of optimal positioning of the specimen it was not always possible to reproduce the entire labyrinthine portion of the canal completely. Most difficult to reproduce were specimens with extremely small vertical diameters and marked caudal sloping of the canal.

Adolescent↗