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At least 577 records · Page 32Linked to original sources
PubMed1977

Surgical anatomy of the temporal bone posterior to the internal auditory canal: an operative approach.

The aim of this study was to describe the anatomical limits of a wedge shaped area of bone lying posterior to the internal auditory canal and to describe the anatomical structures which course through it. One hundred consecutive temporal bones were dissected and topographical dimensions of the posterior wall of the temporal bone were measured along with depth measurements from the posterior fossa wall to the structures of the fundus of the internal auditory canal. A microsurgical technique was then described using the structures within this area as landmarks for specific dissection to the posterior and lateral aspects of the internal auditory canal. Results of 19 tumors have been presented. The status of the facial nerve at the end of surgery and whether or not total tumor removal was possible were discussed.

Arteries↗
PubMed1988

Vertigo in the pediatric and adolescent age group.

Since episodic vertigo in the pediatric and adolescent age group is unusual and therefore not well known to most otolaryngologists, we present six cases to show some of the various presentations and different underlying causes. These cases covered a wide diagnostic spectrum: meningioma, medulloblastoma, childhood migraine with vestibular symptoms, childhood Meniere's syndrome (one case due to perilymph fistula), and benign paroxysmal vertigo of childhood. The two patients with tumor and the patient with perilymph fistula were treated surgically; the other patients are being managed conservatively since these childhood conditions usually tend to diminish with time.

Adolescent↗
PubMed1992

Free-floating endolymph particles: a new operative finding during posterior semicircular canal occlusion.

Most clinicians accept cupulolithiasis as the pathophysiological mechanism underlying benign paroxysmal positional vertigo (BPPV.) According to this theory, a cupular deposit induces a gravitational effect on the posterior canal crista. Posterior semicircular canal occlusion is a new operative procedure for treating incapacitating BPPV. It is postulated that canal occlusion abolishes endolymph movement within the canal, effectively fixing the cupula and rendering it unresponsive to both angular and linear acceleration (gravity). During two recent canal occlusions, abundant "free-floating particles" were identified within the posterior canal endolymph. When changing the position of the canal in the earth vertical plane, these free-floating particles would move under the influence of gravity. The hydrodynamic drag of the particles would induce endolymph movement with cupular displacement leading to the typical response. This finding supports an alternate explanation to cupulolithiasis as the pathophysiological mechanism underlying BPPV.

Aged↗
PubMed1993

Bony dehiscence between singular canal and round window niche.

The incidence of bony dehiscence of the human singular canal was studied by examining 409 human temporal bones obtained from 300 individuals. Such a dehiscence was noted in three (0.7%) of the bones from three (1%) of the individuals, all male, aged 2, 6, and 76 years. All of these bony dehiscences were located between the round window niche and the cribrose area of the singular canal. The finding of a microfissure in the vicinity of the bony dehiscence in two of the three cases indicates that such dehiscences occur independently of microfissures. Although the incidence of bony dehiscences of the singular canal is small, these dehiscences appear to have considerable clinical significance in that they form a communication between the middle and inner ears or possibly between the middle ear and the cerebrospinal fluid space.

Adolescent↗
PubMedDate not supplied

Damage to the stria vascularis in the guinea pig by acute atoxyl intoxication.

The aim of the present study was to show the morphological degeneration at the ultrastructural level, after damaging the stria vascularis experimentally. The acute lesions, after acute atoxyl intoxication, occur after about 12 hours, and begin as a degeneration of both the marginal and the intermediate cells, whereas the basal cells remain mainly unaffected. The severely damaged marginal or intermediate cells may become loosened from the stria vascularis and rejected from it into the endolymphatic space. Under such conditions the basal cells may line the surface facing the endolymph, although this occurs very rarely. Intially, there may be a slight bulging of Reissner's membrane, but soon the membrane becomes depressed, and sometimes a total collapse occurs, with Reissner's membrane flattened over the tectorial membrane against the organ of Corti. It is only seldom that Reissner's membrane touches the strial surface. Mitochondrial degeneration with formation of intramitochondrial inclusion bodies is an interesting early finding in the damage pattern.

Animals↗
PubMedDate not supplied

Histo-physiological relationships in the deaf white cat auditory system.

An investigation is underway in deaf white cats in order to clear up some problems about the timing of cochlear degeneration, the relationships between physiological and histological findings, and the consequential state of central auditory pathways. The first results reported here show that degeneration of sensory structures was much more advanced than physiological results lead us to believe. The possibility of direct fibre stimulation is discussed. Although degeneration of nervous structures was delayed compared with sensory ones, some early abnormalities in myelination were found. In the adult, completely deaf for years, the electrical stimulation of cochlear nuclei evoked normal-looking field responses at the cortical level. Thus some degree of auditory pathway functional integrity appeared even long after they were disconnected from receptors.

Animals↗
PubMedDate not supplied

Sudden deafness in relapsing polychondritis. A scanning electron microscopy study.

The left ear of a 57-year-old female who suffered sudden deafness during the course of relapsing polychondritis was examined under a scanning electron microscope. Marked degeneration of the organ of Corti in all turns and dislocated and encapsulated tectorial membrane were found in the cochlea. Marked decrease in number of the sensory cells in the utricular and saccular maculae and total loss of sensory hair bundles in the ampullary cristae of the semicircular canals were seen in the vestibule. These findings strongly suggest that the cause of sudden deafness in this case might be viral. The usefulness of scanning electron microscopy in human temporal bone pathology is stressed.

Acoustic Maculae↗
PubMedDate not supplied

Ion transport in the cochlea of guinea pig. II. Chloride transport.

The -Cl transport of endolymph--perilymph barrier in guinea pigs was studied by perfusing the perilymphatic space with artificial perilymph containing 36Cl and measuring the uptake of 36Cl in the endolymph. In normal animals no marked difference in -Cl concentration was found between the endodlymph and perilymph. The data showed that the uptake of 36Cl in the endodlymph could be represented by a simple exponential function of the perfusion time, the rate constant being 0.01 min-1. The concentration of 36Cl in the endolymph was greater with perfusion of the scala vestibuli than with perfusion of the scala tympani, indicating the Reissner's membrane is more permeable to -Cl than the rest of the endolymph-perilymph barrier. Anoxia and local application of ouabain decreased the -Cl concentration and 36Cl uptake in the endolymph. Our results imply that the endocochlear potential is the principal driving force for unidirectional flux of -Cl from perilymph to endolymph.

Action Potentials↗
PubMed1979

Methodological aspects of some inner ear vascular techniques.

Modifications of preparation technique assessing cochlear vasculature together with suggestions regarding their applicability to various types of research projects are presented. Detailed information is given regarding the 'soft-surface' dissection and preparation technique along with selected parameters for evaluating the cochlear vasculature. Some basic requirements for any histological technique studying the inner ear blood supply are suggested.

Animals↗
PubMedDate not supplied

Ultrastructural histopathology in a case of human ototoxicity due to loop diuretics.

The temporal bones of a patient who suffered sudden deafness and ataxia after administration of both furosemide and ethacrynic acid, were prepared for light and electron microscopy. There was no loss of hair or supporting cells. However, some hair cells, in both the vestibular neuroepithelium and the organ of Corti, particularly in the basal turn, were more densely staining and more granular than normal. Membrane whorls also were common within mitochondria of such cells. The endoplasmic reticulum of some spiral ganglion cells was dilated. The major cytologic changes were found in the stria vascularis of the cochlea and dark cell areas of the vestibular system. There was marked dilatation of the intercellular fluid spaces, consistent with the biochemical observation that loop diuretics interfere first with enzyme systems responsible for fluid transport within the inner ear.

Cochlea↗
PubMed1984

Ultrastructural study of the effect of acute hyper- and hypotension on the stria vascularis and spiral ligament.

The effects of acute hyper- and hypotension on the stria vascularis and spiral ligament of the rat were studied electron microscopically with the horseradish peroxidase (HRP) tracer method. Acute hypertension was induced by i.v. infusion of methoxamine chloride (Mexan), and acute hypotension by i.v. infusion of a ganglion-blocker (Arfonad) and by venesection. In both acute hyper- and hypotensive experiments, a large amount of leaked HRP spread into the intercellular spaces until it was stopped by tight junctions bordering the stria vascularis. The stria capillary endothelium displayed a dense distribution of labelled vesicles, which suggests increased vesicular transport. There was no extravasation of HRP from capillaries in the spiral ligament, despite the presence of some labelled pinocytotic vesicles. The present paper deals with the discovery of enhanced capillary permeability of the stria vascularis under acute hyper- and hypotension, and makes comparison between acute hyper- and hypotension in order to define the function of the stria vascularis.

Animals↗
PubMedDate not supplied

The microsphere surface technique for evaluation of cochlear vessels and circulation. A preliminary report.

A new technique for the evaluation of cochlear microcirculation and cochlear vessels is described. This method is a modification of two previously used techniques, the "soft-surface-specimen method" and the "microsphere method". In this preliminary paper it was found that the microspheres were easily visualised in all cochlear tissues. The absolute and relative distribution of microspheres was calculated. The method appears promising for experimental investigations of cochlear microcirculation.

Animals↗
PubMedDate not supplied

Regeneration of Reissner's membrane.

Repair of Reissner's membrane following rupture by an excess of endolymph (humans) or by loud sounds (animals) has been reported, but little is known about the process itself. In this study the repair has been examined in a series of guinea pigs by conventional histology and light microscopy. The spiral limbus appears to be involved in normal maintenance of the membrane and the suprastrial area of spiral ligament seems to dominate the process of repair.

Acoustic Stimulation↗
PubMedDate not supplied

Comparative ototoxicity of furosemide and piretanide.

The purpose of these studies was to compare the ototoxicity of piretanide to that of furosemide in the chinchilla. Chinchillas weighing 400 to 700 g were anesthetized with ketamine plus pentobarbital. Endocochlear potential (EP) was measured continuously by the round window approach using glass microelectrodes. Piretanide or furosemide injected through a jugular vein catheter in adults range from 10-100 mg/kg. Little or no change in EP was noted with doses below 15 mg/kg of either diuretic. The overall pattern of decline of EP was rather similar in piretanide-treated and furosemide-injected animals, and it was interesting to find that the dose-ototoxicity response curve for piretanide was similar to that for furosemide. The diuretic effect of equal ototoxic doses of either diuretic was equivalent. Both diuretics cause a decrease of endocochlear potential when applied locally to the round window membrane of the chinchilla as well as by systemic administration. These findings suggest that piretanide and furosemide have approximately the same propensity for ototoxicity.

Administration, Topical↗
PubMedDate not supplied

The change in the electrical resistance of the scala media produced by vasopressin.

The electrical resistance of the scala media (Rm) in the basal turn of the guinea pig was measured during perilymphatic perfusion with vasopressin. As the endocochlear potential (EP) diminished under the influence of vasopressin (0.1 mM), so the Rm increased. The Rm decreased when the EP decreased by vasopressin recovered above the pre-asphyctic level after the termination of temporary asphyxia. The present study demonstrates that the EP decrease produced by vasopressin is associated with the increase in Rm.

Animals↗
PubMed1988

Effects of flunarizine on induced nystagmus and cochlear blood flow.

The effects of flunarizine on induced nystagmus and cochlear blood flow were compared with those of cinnarizine and diphenidol. Flunarizine significantly inhibited caloric (cool water)-induced nystagmus frequency and duration of nystagmus in rabbits at 5 mg/kg i.v., whereas cinnarizine and diphenidol only slightly decreased the frequency of nystagmus at 5 mg/kg, i.v. As for optokinetic stimuli-induced nystagmus in rabbits, flunarizine significantly decreased the amplitude of nystagmus at 2.5 mg/kg i.v., and cinnarizine and diphenidol inhibited nystagmus at 5 mg/kg, i.v. Flunarizine had no effect on nystagmus induced by electrical stimulation of the lateral geniculate body in rabbits at doses up to 5 mg/kg, i.v. Flunarizine increased the cochlear blood flow in anesthetized guinea pigs dose-dependently (0.312-1.25 mg/kg i.v.) On the other hand, cinnarizine (0.625-2.5 mg/kg i.v.) and diphenidol (0.625-2.5 mg/kg i.v.) increased cochlear blood flow, but the duration of action of both cinnarizine and diphenidol was shorter than that of flunarizine at the same dose. As stated above, flunarizine inhibited nystagmus experimentally induced by caloric or optokinetic stimuli. Increased cochlear blood flow suggested that the enhancement of vestibular blood flow might play an important role in the treatment of vestibular dysfunctions with this drug.

Animals↗