Predictive factors for success with a cochlear implant.
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Adult↗
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Maintenance of hydrostatic pressure gradients in the membranous labyrinth.
In normal guinea pig ears, hydrostatic perilymphatic pressure is equal to endolymphatic pressure. Alterations of perilymphatic pressure induced, for example, by laceration of the round window membrane are transmitted immediately to the endolymphatic compartment, probably via Reissner's membrane. In guinea pigs with experimental endolymphatic hydrops, however, pressure gradients between the endolymph and perilymph remained preserved after rupture of the round window membrane. This is considered as further evidence that after long-standing distention of Reissner's membrane the membranous labyrinth loses its ability to equalize endolymphatic and perilymphatic pressure.
Animals↗
Equilibrium of inner and middle ear pressure.
Global balance of inner and middle ear pressure is controlled by the cerebrospinal fluid inside and the atmospheric pressure outside. The cochlear and vestibular aqueducts and the Eustachian tube, connected by a one-way communication, provide a fine control over inner and middle ear pressure.
Animals↗
Conservative management of inner ear barotrauma resulting from scuba diving.
Fourteen patients who experienced inner ear barotrauma (IEBT) while scuba diving were examined shortly after the episode and were followed up until symptoms resolved or stabilized. On the basis of these observations and a review of the literature, three types of IEBT are hypothesized that usually result from forceful autoinflation of the middle ear: (1) hemorrhage within the inner ear, (2) labyrinthine membrane tear, and (3) perilymph fistula through the round or oval window. Presenting symptoms, treatment regimens, and final results are detailed.
Adolescent↗
Histopathology of residual and recurrent conductive hearing loss after stapedectomy.
HYPOTHESIS: Histopathologic examination of temporal bones from patients who had undergone stapedectomy may provide information concerning the causes of both residual and recurrent conductive hearing loss (CHL). BACKGROUND: Although closure of the air-bone gap to within 10 dB occurs in approximately 90% of primary stapedectomies, a residual CHL occurs in approximately 10% and recurrent CHL may occur in up to 35% of cases. Putative causes of failure of surgery as determined during revision include erosion of the incus, bony regrowth at the oval window, and displacement of the prosthesis. Most reports on the histopathologic findings of temporal bones from such patients have focused on complications of surgery, with little attempt to correlate postoperative air-bone gap with the observed histopathology. METHODS: A retrospective review of the author's collection of temporal bones ascertained 22 cases with postoperative CHL of 10 dB or greater (air-bone gap averaged at 500, 1,000, 2,000, 3,000, and 4,000 Hz, using postoperative air- and bone-conduction levels) after stapedectomy. These temporal bones were prepared by standard methodology for light microscopy. RESULTS: Of the 22 cases with postoperative CHL equal to or greater than 10 dB, there were 19 with residual CHL, 2 with recurrent CHL, and 1 with both residual and recurrent CHL. The most common histopathologic correlates of residual and recurrent hearing loss included resorptive osteitis of the incus (64%); obliteration of the round window by otosclerosis (23%); the prosthesis lying on a residual footplate fragment (23%); the prosthesis abutting the bony margin of the oval window (18%); adhesions in the middle ear (14%); and new bone formation in the oval window (14%). CONCLUSIONS: Histopathologic examination of temporal bones from patients who in life had undergone stapedectomy provides useful information concerning causes of both residual and recurrent CHL. These data provide a basis for improving both surgical technique and prosthesis design.
Adult↗
CT and MR imaging of intralabyrinthine schwannoma: report of two cases and review of the literature.
Two cases of intralabyrinthine schwannoma were studied with computed tomography (CT) and magnetic resonance (MR) imaging. On CT scans, a soft-tissue mass was identified in the round window niche in both cases. Widening of the basilar turn of the cochlea and characteristic erosion of the promontory were noticed in one case. Preoperative MR imaging (performed in only one case) revealed a soft-tissue mass in the labyrnth, extending into the round window niche. Findings at CT and MR imaging are discussed, and a differential diagnosis is given. The literature is reviewed. The authors' findings suggest that CT and MR imaging may prove very valuable in the previously difficult preoperative diagnosis of these tumors. In the setting of progressive sensorineural hearing loss, atypical Meniere disease, or recurrent vertigo, the presence of a mass in the labyrinth or labyrinthine windows- delineated on CT or MR images, despite a normal internal auditory canal, cerebellopontine angle, or brain stem - is highly suggestive of intralabyrinthine schwannoma.
Aged↗
Histological evaluation of damage in cat cochleas used for measurement of basilar membrane mechanics.
Cochleas utilized in basilar membrane vibration measurements were examined histologically using an epon-embedded surface preparation technique. The amount of damage observed at both the apical and basal ends of the cochleas was variable. The apical damage was probably caused by large, low-frequency movements of the basilar membrane. The basal damage was due to trauma produced directly by the surgical and experimental procedure. The sharpness of turning observed in the basilar membrane frequency response was found to be inversely related to the extent of histological damage.
Animals↗
Pathology as it relates to surgery of Menière's disease.
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Aged↗
The anatomical relationship of the middle ear and the jugular bulb.
The authors have studied the relationship of the superior jugular bulb with the cavity of the middle ear through the examination of 200 temporal bones. It was observed that the jugular fossa presents a prominence in the tympanic cavity in 54 (27%) cases, and was also found dehiscenses on the osseous wall which protects the bulb (in 2 cases) and absolute absence of this wall in one case. It was verified the variability of the degree of exposure of both, the hypotympanum and the fossula of the cochlear fenestra by the prominence of the jugular fossa.
Adult↗
Pediatric cochlear implantation. Radiologic observations of skull growth.
We investigated the effects of long-term implantation of auditory prostheses on skull growth in young animals. Four monkeys were implanted with dummy cochlear implants at 6 months of age. To simulate implantation in children, the bed for the receiver-stimulator or interconnecting plug was drilled across a calvarial suture down to the underlying dura. Plain skull roentgenograms were periodically taken to monitor head growth for up to 3 years after implantation. These longitudinal measurements revealed no significant asymmetric skull growth. Postmortem measurements using computed tomographic scans confirmed these results and showed no significant difference in the intracranial volumes between the implanted and control sides of each animal or between experimental and nonimplanted control monkeys. These results suggest that long-term cochlear implantation in very young children will not cause any significant deformity of the skull.
Animals↗
Cholesteatoma in children: is the disease different in childhood?
During the early phase of the development of the temporal bone the correlation between the bone growth and the formation of the air-filled spaces--disturbed or undisturbed--is decisive for development of even hidden and neglected forms of middle ear cholesteatomata. The second phase of the development of the temporal bone is determined by a slower rate of bone growth when the mucociliary system has to develop its immunobiological capacities. It becomes obvious that the cholesteatoma matrix and perimatrix will find favourable requirements during this early period of life for a rapid spread since the air-filled spaces have not yet reached their final size. Also the correlation to the gas volume will be different when the ratio of the air flow changes.
Air Pressure↗
Obliteration of the ductus reuniens.
The ductus reuniens was successfully obliterated in 52 guinea pig ears. Histopathological study showed that a majority of these specimens demonstrated cochlear hydrops, saccular collapse and normal utricle. These results support the theory of longitudinal flow of endolymph from the cochlea toward the endolymphatic sac via the ductus reuniens and saccule. A major source of endolymph in the saccule appears to be the scala media. In another set of 11 animals in which the ductus reuniens was first obstructed and two months later the endolymphatic duct was blocked, endolymphatic hydrops was shown in the cochleae, saccules, and utricles of all but one. The evidence suggests that cochlear hydrops was caused by obliteration of the ductus reuniens, and the saccular and utricular hydrops occurred subsequently as the result of blockage of the endolymphatic duct. Remnants of otolithic membrane which were attached to the distended saccular wall indicate that the membrane which had collapsed onto the macula after obliteration of the ductus reuniens is capable of subsequent distension. This experiment supports the concept of endolymph flow from the utricle and canals toward the endolymphatic sac. A blocked cutus reuniens might also explain the pathophysiological basis for the auditory form of Meniere's disease.
Animals↗
Workshop: direct electrical stimulation of the inner ear for the relief of tinnitus.
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Animals↗
[Ear canal atresia, to operate or not?].
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Adolescent↗
Ototoxicity of propylene glycol in experimental animals.
The ototoxicity of antibiotics given either systemically or topically has been recently recognized. However, the ototoxicity of topically applied alcohols and other solvents used as vehicles for drugs has not been well recognized. One of the most common solvents, propylene glycol, was chosen for this study, and this agent in various concentrations was instilled into the middle ear of guinea pigs and chinchillas for various periods of time. Its effect on the function of the cochlea was studied as well as the histopathologic changes in the temporal bones. Deterioration of the cochlear microphonics and the endocochlear direct current potential was found. A 10 per cent solution applied for six days caused a reduction in the cochlear microphonics. Fifty per cent or stronger solution always caused a reduction in the cochlear microphonics. The deterioration in the cochlear microphonics persisted one month. Dose related changes in the endocochlear potential were noted. Morphologic changes were severe and included granulation tissue in the middle ear and destruction and ossification of the auditory bulla and bony cochlea. Propylene glycol should not be used in the ear that has a perforation of the tympanic membrane.
Animals↗
Inferior mastoidectomy-hypotympanic approach for surgical removal of glomus jugulare tumors: an anatomical and radiologic study emphasizing distances between critical structures.
The technique of inferior mastoidectomy-hypotympanic dissection, with preservation of the middle and inner ear structures, has been established for radical surgical removal of glomus tumors involving the skull base. In order to study the gross anatomic differences and correlate with the computed tomography (CT) scan, 20 human temporal bones were dissected and accurate measurements between vital structures were made. This study revealed a wide variation in distances between the neurovascular structures, whereas the distances between inner ear structures were not statistically different. This original study of critical distances of gross topographic anatomical structures and CT correlation is very helpful indeed in the understanding of variations found in the surgical removal of lesions involving this important and challenging area of the skull base. The inferior mastoidectomy-hypotympanic dissection has been performed in the removal of six suitable tumors involving the jugular bulb area. This technique, combined with upper cervical dissection, is very useful for the radical removal of such neoplasms with preservation of external and middle ear structures as well as the function of the facial, eighth, and other lower cranial nerves.
Adult↗
Temporal bone histopathology of atresia auris congenita with chromosome aberration.
Temporal bone findings in two infants demonstrating congenital aural atresia with microtia were presented focusing mainly on the external and middle ears. These two cases were proved to have chromosome aberration that is, 13-15 trisomy and extra chromosome in group G individually. Temporal bones showed the multiple anomalies through the external, middle and internal ears. The external canals were filled with connective tissue in one case and with bony plate in the other to form aural atresia. There were no development of the tubotympanic recess in a case of 13-15 trisomy. The oval window area in both cases was poorly developed resulting in a connective tissue fissure in the lateral wall of the vestibule except for one ear, while the round windows were normally formed in all ears. The facial nerves showed an abnormal running course without forming the geniculate ganglion and the horizontal segment. These findings indicate that the structures derived from the second branchial arch might be more deeply involved than the first one in the congenital aural atresia.
Chromosome Aberrations↗
Differences in the cochlear degeneration pattern in the guinea pig as a result of gentamicin and cis-platinum intoxication.
This study gives the results of a series of studies on inner ears carried out with the help of microdissections and surface preparations. The total degeneration patterns of the cochlea of the guinea pig due to two different ototoxic drugs were investigated with this technique. Clear differences between the results of the ototoxic drugs (gentamicin and cis-platinum) in the inner ear were observed. Gentamicin has a 'typical starting point' of degeneration on the basilar membrane. From this 'degeneration point' the loss of hair cells progressed towards the round window (fast) and the apex (slowly). The stria vascularis showed no signs of degeneration due to gentamicin. Reissner's membrane, on the other hand, showed cellular vacuolization of the endolymphatic cells. Cis-platinum (DDP) showed no 'degeneration point'; the loss of hair cells was found over the complete length of the basilar membrane, with a preference for the basilar turn. The stria vascularis, on the other hand, showed severe degenerative changes due to DDP, whereas Reissner's membrane showed no change. In using the microdissection technique we were in a position to discover these differences between the two ototoxic drugs.
Animals↗