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At least 163 records · Page 9Linked to original sources

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↗

Round window rupture.

Eight patients suffered sudden sensory neural hearing losses associated with exertion or trauma; all were found at tympanotomy to have round window membrane ruptures with leakage of perilymph. Operative findings, with audiometric, radiological and electrocohleographic results are shown. The aetiology is discussed, with particular reference to diving techniques and to the cochlear aqueduct.

Adult↗

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↗

Congenital cerebrospinal fluid fistulae of the petrous temporal bone.

Spontaneous cerebrospinal fluid fistulae from the subarachnoid space into the middle ear cavity may be classified as perilabyrinthine or translabyrinthine. The very rare perilabyrinthine group, through bony defects close to but not involving the labyrinth, usually have normal hearing initially. The commoner translabyrinthine group are nearly always associated with anacusis, severe labyrinthine dysplasia and a route via the internal auditory meatus. The labyrinthine deformity is more severe than the type classically described by Mondini, and evidence of a dilated cochlear aqueduct in these cases is also unconvincing.

Cerebrospinal Fluid Otorrhea↗

Effects of posture and age on tympanic membrane displacement measurements.

This study used changes in posture to investigate the transmission of cerebro-spinal fluid (CSF) pressure changes to the cochlear fluids in subjects falling into two age groups. Results were obtained from 32 subjects: 16 aged 19 to 32 years and 16 aged between 40 and 63. Measurements were made with the subject sitting upright and then at 63 degrees to the vertical, using a technique which measures displacement of the tympanic membrane in response to acoustic stimulation of the stapedial reflex. Changes in such measurements are believed to represent changes in perilymphatic fluid pressure. Statistical analysis of the results showed the magnitude of changes in Tympanic Membrane Displacement (TMD) measurements with postural change to be smaller in the older group than in the younger age group. In addition, a larger proportion of the older subjects showed no change in TMD measurements with change in posture. The proportion of subjects in each age group who showed no change in TMD measurements with change in posture was similar to the proportion of temporal bones of subjects of similar ages that had non-patent cochlear aqueducts as determined by a previous histopathological study. Audiometric testing revealed a link between hearing threshold and presumed patency of the communication routes between cochlear and cranial fluids. The magnitude of the tympanic membrane displacement was found to decrease with age in agreement with previous studies showing decrease of stapedial reflex magnitude with increasing age. It is suggested that the communication between cochlear and cranial fluids may be important in the pathogenesis of auditory dysfunction in several patient groups.

Adult↗

No postural effect on middle ear resonance frequency: a pilot study.

A change in body posture from sitting to reclined is known to cause an increase in intracochlear fluid pressure, if the cochlear aqueduct is patent. Previous studies have shown this increase to have an effect on middle ear dynamics. The aim of this study was to investigate whether such increases in cochlear pressure may affect the stiffness of, and hence the resonance frequency of the middle ear. No consistent group or individual differences were shown between the two postural conditions.

Acoustic Impedance Tests↗

Anatomy of the temporal bone: detailed three-dimensional display based on image data from high-resolution helical CT: a preliminary report.

Our purpose was to demonstrate the application of helical computed tomography (CT) for computer graphics of the normal temporal bone with special regard to inner ear structures. Three-dimensional reconstruction of temporal bones was performed from helical CT data on 41 patients with various otologic diseases. Image postprocessing was carried out on an independent work station. In contrast to former surface-rendered three-dimensional visualizations of the temporal bone, a volumetric-rendering algorithm was used. This technique allows automated segmentation, thresholding, and simultaneous visualization of different planes (cube-cutting) in near-real time. We were able to demonstrate the three-dimensional display of the labyrinth during clinical routine. Anatomic details (internal auditory canal, cochlea, vestibulum, semicircular canals, distal part of the vestibular aqueduct, complete ossicular chain, fallopian canal, internal carotid canal) were comprehensively demonstrated by interactive segmentation or thresholding. Difficulties were found in three-dimensional delineation of the complete vestibular and cochlear aqueduct, as well as the modiolus. Initial experience with an advanced helical CT-based three-dimensional display showed excellent images of temporal bone anatomy. Validation studies with correlative histologic sections and surgical dissections remain to be done.

Ear, External↗

Communicatory routes connecting the middle ear, the inner ear and the subarachnoid space via perineural space.

Twenty-one rabbits received injection of Indian ink into the stylomastoid foramen. Observation of the serial sections of their temporal bones revealed Indian ink infiltration into the subarachnoid space, along the facial nerve, the auricular branch of the vagus nerve and the tympanic nerve. Along the acoustic nerve, the infiltration was found as far as the fundus of the internal auditory meatus. In some cases, however, Indian ink reached the subarachnoid space and infiltrated into the scala tympani, scala vestibuli and around the saccule by way of the cochlear aqueduct. These routes are suspected to be a course of spreading infection or tumor cells.

Animals↗

Progression of hearing loss in experimental pneumococcal meningitis: correlation with cerebrospinal fluid cytochemistry.

The development of hearing loss and concomitant cerebrospinal fluid (CSF) cytochemical changes in a model of pneumococcal meningitis were examined. Rabbits were injected intracisternally with 10(5) pneumococci. Auditory evoked potentials to clicks and to 10- and 1-kHz tone bursts were recorded hourly; CSF was analyzed every 4 h. Sensorineural hearing loss developed in all animals beginning 12 h after infection and progressed to severe deafness. The onset of hearing loss was preceded by a CSF leukocytosis of > 2000 cells/microL and elevation of CSF protein and lactate concentrations to > or = 1 mg/mL. Temporal bone histopathology showed pneumococci and leukocytes extending from the CSF to the perilymph via the cochlear aqueduct. Hearing loss can develop early in the course of meningitis and is preceded by the abrupt onset of inflammatory changes in CSF. Progression of hearing loss is rapid and proceeds from cochlear base to apex in parallel with the degree of inflammation.

Animals↗

[High resolution MR imaging of the inner ear apparatus using 3D-Fast spin echo sequence].

To evaluate the efficacy of high resolution MR imaging of the inner ear with 3D-Fast spin echo sequence, one volunteer and 12 patients were imaged with a 1.5 T MR scanner. High resolution T2-weighted images were obtained with a head coil in 13 minutes, and the voxel size was 0.39mm x 0.45mm x 1.2mm in most subjects. Original images and maximum intensity projection (MIP) images of the inner ear were evaluated. On original images, the endolymphatic duct was visualized in 72% of subjects, the cochlear aqueduct in 96%, three branches of the cranial nerves in the internal auditory canal in 100%, and flow void of the vessel in the cerebellopontine angle in 100%. On MIP images, more than two cochlear turns were visualized in 92% of subjects, three semicircular canals in 100%, and the anterior and posterior ampulla in 100%. MR imaging of the inner ear with 3D-Fast Spin Echo sequence provides a variety of useful information regarding the anatomy around the inner ear.

Ear, Inner↗

Sudden deafness and facial palsy from metastatic bronchogenic carcinoma.

A 52-year-old man developed sudden total bilateral deafness, and unilateral facial palsy, without other symptoms and findings. He died two months later of of bronchogenic carcinoma metastatic to dura, brainstem, pons, carebellopontine angle, cerebellum and cranial nerves III, VI, VII and VIII. There was bilateral internal auditory canal erosion. Tumour replaced right facial, acoustic and vestibular nerves. Tumour infiltrated spiral ganglion, cochlear nerve, cochlear aqueduct, and destroyed nearly all facial nerve fibres to the level of the stapedius muscle. No tumour cells were found on the left, but few fibres of facial, acoustic and vestibular nerves survived. Both ears showed some cochlear outer hair cell destruction. Metastatic tumour to temporal bone or dura should be considered when loss of peripheral VIIth or VIIIth nerve function occurs.

Brain Neoplasms↗

Treatment and management of perilymphatic fistula: a New Hampshire experience.

From August of 1975 to June of 1990 the author managed 45 cases of spontaneously occurring perilymphatic fistula. Twenty-nine of the 45 cases were reported in 1988. In the series there were eight patients with bilateral involvement, seven with involvement of both oval and round window in the same ear, and seven with fistulas believed to be of congenital origin. Seventeen patients (38%) required revision surgery. Occasionally adjunct modalities (endolymphatic shunt, labyrinthectomy, blocking a cochlear aqueduct, and streptomycin ablation) were used for symptom control. Diagnosis, treatment, and management of these patients is discussed.

Adolescent↗

Volume flow rate of perilymph in the guinea-pig cochlea.

The rate of longitudinal flow of perilymph has been measured using an ionic tracer technique. Spread of the tracer trimethylphenylammonium (TMPA) along the perilymphatic scalae was monitored with ion-selective microelectrodes following injection of a minute bolus (approximately 50 nl) of 150 mM TMPAC1 one turn away. This amount of TMPA had virtually no toxic effect on cochlear function. The spread of tracer by longitudinal volume flow and passive diffusion were separated by comparing tracer movements in both apical and basal directions along the scalae in two groups of animals. Experimental findings were compared with a mathematical model which combined diffusion and volume flow. Our results demonstrated that when electrodes were completely sealed into the cochlea, the rate of longitudinal volume flow in scala tympani was extremely slow, approximately 1.6 nl/min in the apical direction. Longitudinal flow was not detectable in scala vestibuli. When the otic capsule was perforated, flow rates of over 1 microliter/min were recorded in scala tympani, probably as a result of cerebrospinal fluid entry through the cochlear aqueduct. When the cochlea was sealed (with recording electrodes in place) and cerebrospinal fluid pressure was released, there was no significant basally-directed flow of perilymph in scala tympani. These findings support the concept that perilymph composition is maintained by local, cochlear mechanisms which do not involve longitudinal volume flow. They provide strong evidence that perilymph is not secreted in one region and resorbed at a spatially distant site.

Action Potentials↗

Instrumental perforation of the round window. Animal experiments using cochleography and ERA.

The round window membrane of the inner ear of the guinea pig was perforated under Ketanest anaesthesia. A very rapid and almost total loss of cochlear microphonics, auditory nerve action potential and brain-stem response developed. Replacement of the perilymph with Ringer's solution and surgical closure of the membrane damage had no effect on auditory nerve action potential or brain-stem response. Further decline in the amplitude of cochlear microphonics was halted, however. When perfusion of the round window membrane was carried out whilst the bulla was full with Ringer's solution, no essential decline was seen in the amplitudes of microphonics and auditory nerve action. Only brain-stem response was reduced--temporarily by 40% of the original amplitudinal level--but this showed subsequent recovery. Preservation of cochlear microphonics and auditory nerve action after perforation in Ringer's solution, i.e. excluding air, indicates that air entering the scala tympani is the cause of the sudden hearing loss after round window perforation. Using a simple physical model, an attempt is made to demonstrate this process. The anatomic connections between the round window, cochlear aqueduct and scala tympani are discussed, as are the different ways in which the round window membrane can be perforated.

Action Potentials↗

Evaluation of procedures to reduce fluid flow in the fistulized guinea-pig cochlea.

The rate of longitudinal flow of fluid in scala tympani (ST) has been quantified under a number of experimental conditions. The method used to measure flow involved using a tracer ion (trimethylphenylammonium: TMPA) as a volume flow marker. Movement of marked perilymph was monitored by ion-selective microelectrodes which were capable of detecting exceedingly low concentrations of TMPA. Our results show that when the cochlea is perforated at the apex, flow rates of 400-500 nl/min are induced in ST, compared to the normal very slow rate of 2 nl/min when the cochlea is sealed. This artifactual flow of CSF through the perforated cochlea can be reduced to 6.9 nl/min by releasing the hydrostatic pressure of cerebrospinal fluid (CSF) or further reduced to 1.8 nl/min by surgically obstructing the cochlear aqueduct. In addition, we observed no basally-directed flow in ST when the round window (RW) was perforated, demonstrating that perilymph is not produced in volume as previously assumed. This study demonstrates the importance of separating artifactual flows, induced by the experimental procedures required to access the cochlear fluids, from the low flow rates which occur in normal, physiologic conditions.

Action Potentials↗

[Magnetic resonance imaging of the inner ear and its application to cochlear implant candidates].

Magnetic resonance (MR) images of normal and abnormal inner ears obtained with a 1.5T unit without the use of a surface coil were analyzed to evaluate the effectiveness of this method in the screening of cochlear implant candidates. In a series with sixteen normal adult volunteers, 22 to 45 years in age, 100% of the cochleae, vestibules, and lateral and posterior semicircular canals were clearly demonstrated in T2 weighted images. Satisfactory images were not obtained for 22% of the superior semicircular canals, 22% of the cochlear aqueduct, and 81% of the vestibular aqueduct in axial images, but coronal and sagittal reconstructed images by use of a three-dimensional Fourie transformation sequence provided better detectability of these structures. In five ear surgery patients with proven obliteration of the labyrinth, decreased signal intensity was observed in the T2 weighted images. Ten cochlear implant candidates were examined by MRI prior to implantation, and the results were compared with the surgical findings. In two ears in which the cochlea showed a decrease in signal intensity, the cochlea had been obliterated by inflammatory granulations. On the other hand, the lumens of all nine cochleae which were clearly visualized by MRI were found to be patent.

Adult↗

Computed tomography and magnetic resonance imaging of the inner ear.

The majority of temporal bone radiographic studies are obtained either for middle ear and mastoid disease or in the evaluation of retrocochlear pathology. With recent technologic advances, diagnostic imaging of the inner ear has developed an increasing role in the evaluation and management of diseases that affect the cochlea, semicircular canals, and the vestibular and cochlear aqueducts. High-resolution computed tomography (CT) provides excellent detail of the osseous labyrinth, whereas magnetic resonance imaging (MRI) generates images derived from the membranous labyrinth and its associated neural elements. Optimal techniques for obtaining high quality CT and MRI images of the normal and diseased inner ear are presented. CT has proved useful in the evaluation of inner ear malformations, cochlear otosclerosis, labyrinthine fistulization from cholesteatoma, translabyrinthine fractures, otic capsule osteodystrophies, in the assessment of cochlear patency before cochlear implantation, and in the localization of prosthetic devices such as stapes wires and cochlear implants. While MRI produces discernible images of the soft tissue and fluid components of the inner ear, it has yet to demonstrate any unique advantages in the evaluation of inner ear disease. However, MRI produces excellent and highly useful images of the audiovestibular and facial nerves, cerebellopontine angle, and brain.

Cholesteatoma↗

Experimental aural barotrauma. Electrophysiological and morphological findings.

The electrophysiological findings show a time and pressure related decrease in function of the CM and the N1 potentials. Sudden changes were correlated with tympanic membrane perforations. Some of the decreased function is accounted for by middle ear effusion and hemorrhages, reducing mechanically the transmission of sound energy through the middle ear. This was evidenced by an improvement of function when the fluids were removed. Remaining decreases in function were interpreted as a result of influences on the inner ear function or of undisclosed middle ear changes. No differences were noted in cochlear function between animals subjected to sustained or intermittent middle ear pressures. Neither were any morphological differences noted between these two groups in the middle or inner ear. The morphological middle ear findings correlated well with previous clinically and experimentally induced changes with increased/decreased middle ear pressure. The cochlear findings include the interesting observation of an intact round window membrane, a clear endolymph, and a normal Organ of Corti in all cases. Positive findings were a high frequency of hemorrhage, most commonly demonstrated in the scala tympani of the basal turn close to the round window. The origin of the hemorrhages could not be demonstrated with the present investigation. The hemorrhages often appeared to be related to the cochlear aqueduct. The occurrence of hemorrhage was clearly related to increased negative pressure, and the non-existence of hemorrhage was always related to either tympanic membrane perforations or low applied pressure. Further frequent findings were distention, collapse, and rupture of the inner ear membranes which must be interpreted with great circumspection due to the method used. Likewise, some of the pathological cochlear findings may be due to pathological conditions which are not necessarily related to induced middle ear pressure.

Acoustic Stimulation↗