Surgical treatment of hydrops of the labyrinth; surgical destruction of the labyrinth for Ménière's disease.
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Ear, Inner↗
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[Ethmoidal labyrinth. 3. Ethmoidal labyrinth of 4-10-month-old human fetuses].
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Ethmoid Sinus↗
The labyrinth in the making. A study of morphological and physiological features of the labyrinth in the cylostomes.
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Animals↗
Pathology of the membranous labyrinth: comparison of T1- and T2-weighted and gadolinium-enhanced spin-echo and 3DFT-CISS imaging.
PURPOSE: To assess the value of unenhanced T1-weighted images, T2-weighted images, gadolinium-enhanced T1-weighted images, and three-dimensional Fourier transformation-constructive interference in steady state (3DFT-CISS) images in depicting lesions of the membranous labyrinth. METHODS: Six patients were studied using 1-T MR; both enhanced (gadolinium-tetraazacyclododecane tetraacetic acid) and unenhanced images were obtained and different sequences compared to determine which provided the most information. RESULTS: A combination of gadolinium-enhanced T1-weighted and 3DFT-CISS images could depict all membranous labyrinth pathology. Unenhanced T1-weighted images were necessary to exclude spontaneous hyperintensity in the membranous labyrinth. Gadolinium-enhanced T1-weighted images were needed to detect enhancing pathology such as labyrinthitis and tumors inside the membranous labyrinth. In these cases, 3DFT-CISS images allowed immediate differentiation between inflammation and tumor. In temporal bone tumors involving the bony and membranous labyrinth, unenhanced and enhanced T1-weighted images often sufficed to suggest the correct diagnosis. Only 3DFT-CISS images were able to demonstrate small structures (as fistulas) and to help us confirm or rule out obliteration of the labyrinthine fluid spaces. 3DFT-CISS images were necessary to detect small congenital malformations of the membranous labyrinth when only MR was performed. Uncalcified obliteration of the labyrinth fluid spaces could be reliably detected only on 3DFT-CISS images. Here also gadolinium-enhanced T1-weighted images had to be obtained because enhancement of the soft tissues inside the membranous labyrinth had been observed. CONCLUSION: The CISS sequence and enhanced T1-weighted sequence formed the best sequence combination for diagnosis of membranous labyrinth lesions; additional, unenhanced T1-weighted images can help one differentiate labyrinthitis, proteinaceous fluid, subacute hemorrhage, or tumor inside the labyrinth.
Adolescent↗
Carotid labyrinth of amphibians.
The amphibian carotid labyrinth is a characteristic maze-like vascular expansion at the bifurcation of the common carotid artery into the internal and external carotid arteries. The carotid labyrinths of anurans are spherical and those of urodeles are oblong. In the intervascular stroma of both anuran and urodelan carotid labyrinths, the glomus cells (type I cells, chief cells) are distributed singly or in clusters between connective tissue cells and smooth muscle cells. In fluorescence histochemistry, the glomus cells emit intense fluorescence for biogenic monoamines. In fine structure, the glomus cells are characterized by a number of dense-cored vesicles in their cytoplasm. The glomus cells have long, thin cytoplasmic processes, some of which are closely associated with smooth muscle cells, endothelial cells, and pericytes. Afferent, efferent, and reciprocal synapses are found on the glomus cells. The morphogenesis of the carotid labyrinth starts in the larvae at the point where the carotid arch descends to the internal gills. Through the early stages of larval development, the slightly expanded region of the external carotid artery becomes closely connected with the carotid arch. By the end of the foot stage, the expanded region becomes globular, and at the final stage of metamorphosis the carotid labyrinth is close to its adult form. In fine structure, the glomus cells appear as early as the initial stage of larval development. At the middle stages of development, the number of dense-cored vesicles increases remarkably. Distinct afferent synapses are found in juveniles, although efferent synapses can be seen during metamorphosis. The carotid labyrinth is innervated by nerve fibers containing several kinds of regulatory neuropeptides. Double-immunolabeling in combination with a multiple dye filter system demonstrates the coexistence of two different neuropeptides. The amphibian carotid labyrinth has been electrophysiologically confirmed to have arterial chemo- and baroreceptor functions analogous to those of the mammalian carotid body and carotid sinus. The ultrastructural characteristics of the glomus cells during and after metamorphosis suggest that the glomus cells contribute to the chemoreception after metamorphosis. The three-dimensional fine structure of vascular corrosion casts suggests that the amphibian carotid labyrinth has the appropriate architecture for controlling vascular tone and the findings throughout metamorphosis reveal that the vascular regulatory function begins at an early stage of metamorphosis. In addition, immunohistochemical studies suggest that the vascular regulation in the carotid labyrinth is under peptidergic innervation. Thus, the multiple functions of the carotid labyrinth underline the importance of this relatively small organ for maintenance of homeostasis and appropriate blood supply to the cephalic region.
Amphibians↗
A human temporal bone study of acute bacterial meningogenic labyrinthitis.
It is well established that sensorineural hearing loss (SNHL) is an important sequela of acute bacterial meningitis. Previous human temporal bone histopathologic studies have suggested that such hearing loss is due to labyrinthitis. This study involved a detailed and systematic evaluation of the auditory and vestibular end-organs in 41 human temporal bones from patients with acute bacterial meningitis, aimed at describing the spectrum of histopathologic changes within the labyrinth, ascertaining likely routes for spread of infection from the meninges to the inner ear, and comparing the data from humans with those described in a rabbit model of meningogenic labyrinthitis. Our study revealed the following: (a) Suppurative labyrinthitis occurred in 20 (49%) bones. Of these 20 bones, the cochlea was affected in all, whereas the vestibular organs were involved in 10. Eosinophilic staining of inner ear fluids without the presence of inflammatory cells (so-called "serous" labyrinthitis) occurred in 14 of the remaining 21 bones. This staining occurred primarily within the vestibular system. Its significance and pathogenesis remains unknown; (b) Sensory and neural structures of the inner ear appeared intact in the majority of specimens, including bones with suppurative labyrinthitis and those with eosinophilic staining of inner ear fluids. This finding raises the possibility of preventing or reversing SNHL by therapeutic intervention. Spiral ganglion cells were severely degenerated in 12% of bones, indicating a retrocochlear site of hearing loss in addition to the cochlea. This subset of patients may perform poorly after cochlear implantation; (c) It has been traditionally assumed that irreversible and permanent SNHL is caused by suppurative labyrinthitis, whereas reversible SNHL is caused by serous labyrinthitis. Our findings question the validity of these assumptions; (d) The data were consistent with the hypothesis that both the cochlear modiolus and cochlear aqueduct can serve as potential pathways for spread of infection from the meninges to the inner ear; (e) There were many similarities in the histopathology of the inner ear in humans when compared with the rabbit model of meningogenic labyrinthitis. A notable difference was that the cochlear aqueduct appeared to be the sole pathway for spread of infection in the rabbit, whereas in the human, both the modiolus and aqueduct were possible pathways.
Adolescent↗
Histopathologic correlation of spiral ganglion cell count and new bone formation in the cochlea following meningogenic labyrinthitis and deafness.
Bacterial meningitis is a common cause of profound deafness and, hence, a common cause of deafness in published series of patients treated with a cochlear prosthesis. Labyrinthitis ossificans is a common finding in meningogenic labyrinthitis and has been considered a relative contraindication to cochlear implantation. In the present study, the numbers of remaining spiral ganglion cells in cases of meningogenic labyrinthitis were correlated with the severity of new bone formation within the inner ear. Six temporal bones in which profound sensorineural hearing loss occurred in life secondary to meningogenic labyrinthitis were studied by serial section light microscopy. Some degree of labyrinthitis ossificans was found in four of six. There was a moderately strong negative correlation between the number of years of total deafness and the percentage of normal of the remaining spiral ganglion cell count. There was a strong negative correlation between the degree of bony occlusion by labyrinthitis ossificans and the normality of the spiral ganglion cell count. The percentage of bony occlusion of the membranous labyrinth increased with the years of total deafness. The significance of these findings for cochlear implantation of individuals with meningogenic labyrinthitis is discussed.
Aged↗
Labyrinthitis in chronic otitis media.
Labyrinthitis is the most frequent complication of chronic otitis media (COM). Retrospective analysis of 1,210 patients operated due to COM was carried out. Circumscribed labyrinthitis was found in 17.2% and deafness in 1.2% of patients. To evaluate the effect of labyrinthitis on bone conduction (BC) we measured BC threshold in a group of 140 patients with unilateral COM without labyrinthitis and in a group of 42 patients with unilateral COM with labyrinthitis. BC threshold of the healthy ear was subtracted from the BC threshold of the affected ear in the same patient to eliminate presbyacusis. There was no significant difference in bone conduction threshold between the patients with circumscribed labyrinthitis and patients with COM without labyrinthitis. The incidence of labyrinthitis was higher in patients with cholesteatoma than in patients without cholesteatoma. Management of labyrinthine fistula is presented.
Adolescent↗
The significance for postoperative hearing of preserving the labyrinth in acoustic neurinoma surgery.
Among 186 patients with preoperative hearing, a total of 189 acoustic neurinomas were removed through a lateral suboccipital approach with anatomical preservation of the cochlear nerve. Functional hearing was preserved in 92 (49%) of these patients; despite anatomical preservation of the cochlear nerve, deafness was the result in 51% of the series. Many factors have been considered to cause hearing loss in patients whose cochlear nerve was intact after surgery; these include nerve retraction, nerve or cochlear ischemia, overheating and vibration damage to the nerve, and opening of the labyrinth. To evaluate the significance of injury to the labyrinth in postoperative hearing loss, a prospective study was undertaken. High-resolution computerized tomography studies through the inner ear with bone algorithm were performed pre- and postoperatively. The postoperative status of the labyrinth was classified into three patterns: intact, fenestrated, and widely opened. Injury to the labyrinth occurred in 30% of the cases. The most frequently injured labyrinth structures were the crus commune of the posterior and superior semicircular canals (52%), the posterior semicircular canal (23%), the vestibule (21%), and the superior semicircular canal (4%). A statistically significant relationship was found between injury to the labyrinth and deafness, elevated thresholds, and lower discrimination values at pure-tone audiograms and speech audiometry (p < 0.0001). The degree of the injury (comparison between fenestration and wide opening of the labyrinth) was also significantly related to postoperative deafness (p < 0.0001). Disturbance of the inner-ear fluids was considered to be the cause of the hearing loss. In 12 patients labyrinth injury was not associated with deafness. This finding may support the existence of mechanisms of cochlear protection. The homeostatic function of the endolymphatic sac was considered to play an important role in recovery of damaged hearing in these 12 cases.
Adolescent↗
Topographic analysis of inner ear lesions in profoundly deafened patients with tympanogenic and meningogenic labyrinthitis using three-dimensional magnetic resonance imaging.
OBJECTIVE: High-resolution magnetic resonance imaging (MRI) provided clear images of three-dimensional (3D) reconstruction of the inner ear in candidates for cochlear implantation. In this study. semiquantitative analysis of the 3D MRI findings was performed to investigate topographic lesions of the inner ear caused by tympanogenic and meningogenic labyrinthitis. STUDY DESIGN: This was an observational study. SETTING: The study was performed in an academic, comprehensive, multispecialty group practice. PATIENTS: Postlingual deafened patients with cochlear implantation. The cause of deafness was tympanogenic or meningogenic labyrinthitis. INTERVENTION: High-resolution 3D MRI and postoperative speech recognition tests were used. RESULTS: Abnormal findings in the inner ear detected with MRI were found before surgery in 58.3% of the patients with meningogenic labyrinthitis, although the incidence was lower in patients with tympanogenic labyrinthitis. Abnormal MRI findings were frequently observed in the cochlear basal turn and semicircular canals more than in the middle and apical turn in cases with meningogenic etiology. Patients with tympanogenic labyrinthitis suffered less with a vestibular apparatus than did those patients with meningogenic labyrinthitis. Regarding the analysis of the inner ear lesions at the implanted side, the postoperative speech recognition ability did not correlate to the extent of abnormal MRI findings of the implanted ear. CONCLUSION: Improvement in 3D MRI technology provided an accurate preoperative picture of the inner ear apparatus. In cochlear implant patients with infectious labyrinthitis, the extent of the inner ear lesion detected with 3D MRI was different among etiologies of deafness.
Adult↗
Morphogenesis of the carotid labyrinth in the bullfrog, Rana catesbeiana, during larval development and metamorphosis.
Morphogenesis of the carotid labyrinth in Rana catesbeiana during larval development and metamorphosis was studied using vascular corrosion casting and scanning electron microscopy. The carotid labyrinth was formed at the point where the carotid arch descends to the internal gills. The transformation of the appearance of the carotid labyrinth can be summarized in six phases. 1. Through the early stages of larval development (stages I-V), the slightly expanded region of the external carotid artery becomes closely connected with the carotid arch, and these two arteries are joined by small channels on their opposing faces. 2. By the last stage of foot stages (stage XVII), the expanded region becomes globular. 3. At the middle of the metamorphic stages (stage XXII), many protuberances appear on the surface of the globular expansion. 4. At stage XXIII, these form a rudimentary vascular maze. 5. At stage XXIV, this globular expansion is completely surrounded by a simple maze-like structure that resembles the carotid labyrinth in adults. The origin of the internal carotid artery is located within the vascular maze. 6. At the final stage of metamorphosis (stage XXV) the carotid labyrinth is nearly completed. The vascular ring and vascular routes found in the adult can be recognized at the proximal and distal end of the labyrinth, respectively. These findings suggest that the premetamorphic carotid labyrinth has a vascular regulatory function.
Animals↗
Finding paths in a labyrinth based on reaction-diffusion media.
During the past few decades, many proposals were made on how to take an effective solution for finding a path in a labyrinth, one of the most well known problems of high computational complexity inherent in information processing by biomolecular and biological entities. In particular, attempts were made to use a technique attractive enough for solving this problem based on wave processes in reaction-diffusion media. Trigger waves in reaction diffusion systems spread simultaneously through all paths of the labyrinth in a highly parallel mode. Regretfully, the velocity of these waves is extremely low which gave no way for the practical implementation of this technique until now. An effective 'hardware' system was designed which was capable of finding a path in a labyrinth using fast phase waves. Three principal points were assumed as a basis for this design, i.e. (1) hybrid architecture that combined an information processing reaction-diffusion medium which performs operations of high computational complexity with a digital computer carrying out supplementary image processing operations; (2) light-sensitive information processing media of Belousov-Zhabotinsky type that enables the simulation of the labyrinth and spreading wave evolution by their images stored in the medium and reduces the problem to the image processing operations; (3) fast light-induced phase wave processes that spreads through the labyrinth in several seconds instead of hours which is typical for trigger waves inherent in reaction-diffusion media. These fundamentals along with the additional procedure of testing for labyrinth fragment connectness provided us with the opportunity to solve labyrinth problems.
Computer Simulation↗
Tonic influence from one labyrinth onto the contralateral one. An electrophysiological study in the frog.
In the frog's isolated head preparations, spontaneous activity was recorded from the whole nerve of the left horizontal semicircular canal (HC) for 6 min before and 16 min after destruction of the right labyrinth by heating or administration of d-tubocurarine (0.5 microliter, 5.10(-6)M) into the perilymph of the right labyrinth. Just after destruction on the right labyrinth, spontaneous activity of the left HC nerve abruptly increased by 20-400% in 24 preparations out of the 40 studied; activity then increased slowly and regularly and in most cases reached a steady level. In the 16 other preparations such destruction had no effect (15 preparations) or elicited a slight decrease of the HC nerve activity (one preparation). After curare administration, the spontaneous activity of the left HC nerve decreased by 20-100% in 27 preparations out of the 40 studied; in most cases such a decrease was reversed 25-80 min after administration of the drug. The spontaneous discharges were unaffected in 11 preparations and slightly increased in the two others. Destruction of the right labyrinth or administration of curare never modified spontaneous activity recorded from the left HC nerve when the connections between the two labyrinths had been interrupted either by sagittal section of the medulla oblongata or section of the right vestibular nerve close to the brain stem. These results demonstrate that one labyrinth has a tonic inhibitory influence on the contralateral one.
Animals↗
A combined SEM and TEM study on the basal labyrinth of the collecting duct in the rat kidney.
The three-dimensional ultrastructure of principal cells in the rat renal collecting duct was studied by scanning electron microscopy (SEM) using the NaOH digestion technique and the aldehyde prefixosmium-DMSO-osmium method, as well as by transmission electron microscopy (TEM). Special reference was given to the basal labyrinth of the cells and its numerous ruffles and infoldings of the basal plasma membrane. Observations showed that, as the collecting duct descends from the cortical collecting duct (CCD) to the terminal portion of the inner medullary collecting duct (t-IMCD), the pattern of the labyrinth gradually simplified and the ruffles grew thinner. In the CCD, the labyrinth was conspicuously complicated in structure, being formed of tightly arranged ruffles of uniform shape and thickness (70 nm). From the outer medullary collecting duct (OMCD) to the initial portion of inner medullary collecting duct (i-IMCD), the labyrinth became less complicated due to the mingling of wide flattened ruffles. Also, the basal infoldings were reduced in depth (from 700 nm in CCD to 500-600 nm in i-IMCD). In the t-IMCD, the labyrinth was rudimental, and instead presented small grooves (300 nm in depth) which corresponded to indentions of the basal plasma membrane. The regional simplification of the labyrinth was accompanied by morphological changes in mitochondria suggesting their functional decline: the electron density and number of cristae were reduced, these being changed in shape from plate-like to vesicular. These morphological data readily account for the potential for active transport by the collecting duct, which is highest in the CCD and is decreased towards the t-IMCD, and which may function merely as an excretory duct of urine from the papilla. The present study three-dimensionally demonstrates fine-structural heterogeneity in different segments of the collecting duct of the rat kidney.
Animals↗
On the vascular architecture of the carotid labyrinth in Cynops pyrrhogaster and Onychoactylus japonicus.
The fine vascular arrangement of the carotid labyrinth in two species of urodeles, Cynops pyrrhogaster and Onychodactylus japonicus was investigated. India ink-gelatin injected preparations were examined under the dissecting microscope. Resin casts of the blood vessels prepared using the method of MURAKAMI (1971) were observed in the scanning electron microscope. In both species, the common carotid artery terminated in the central chamber from which arose two retia mirabilia, i.e. an external carotid rete and an internal carotid rete. The external carotid artery arose recurrently from the external carotid rete, whereas the internal carotid artery received vessels from the internal carotid rete which apparently occupied more than two thirds of the carotid labyrinth. The present observations indicate that the previous descriptions of the urodele carotid labyrinth should be corrected: a vascular ring exists around the common carotid artery and the latter shows a corresponding narrowing at the entrance to the carotid labyrinth; the vascular ring forms the most proximal part of the external carotid rete; the central chamber occupies only a part of the proximal end of the carotid labyrinth; the internal carotid rete and the external carotid rete constitute a continuous rete mirabile; and a distinct furrow exists in the boundary between these two portions of the rete mirabile. Individual variations were frequently encountered, but were confined to the external carotid artery and its tributaries. The complicated and elaborate vascular architecture of the amphibian carotid labyrinth suggests that this organ should exert blood-flow regulating the probably other unknown functions as an effector organ in addition to its accepted activity as a chemo- and baro-receptor.
Ambystoma↗
[Changes in the blood-labyrinth barrier. Assessments by magnetic resonance].
PURPOSE: Recent progress in magnetic resonance imaging (MRI), with contrast-enhanced and steady-state sequences, allows fine depiction of labyrinth abnormalities related to neoplastic, inflammatory, ischemic, degenerative or traumatic disorders. We examined 488 patients with sensorineural hearing loss, vertigo or dizziness, but normal CT findings, to evaluate MR capabilities in showing labyrinth conditions. MATERIAL AND METHODS: January 1994 to May 1998, four hundred and eighty-eight patients with labyrinthine symptoms were submitted to CT. Sixty-eight of them, with normal CT findings, were also examined with MRI, which was performed using quadrature head or surface coils and a single dose (0.1 mmol/kg) Gd-DTPA administration. Conventional T1 and T2 high resolution SE images were acquired. The labyrinth was studied of 52 patients with normal CT findings and no abnormalities in the cerebello-pontine angle or internal auditory canal. RESULTS: Fourteen of 52 patients (27%) exhibited labyrinth enhancement from tumor (5%), hemorrhage (3%), infection (15%), surgical (2%) or radiosurgical (2%) procedures. GRASS sequences allowed differentiation of mass lesions (e.g., tumors, clots) from other conditions. CONCLUSION: Generally the labyrinth exhibits no contrast enhancement even after a triple Gd-DTPA dose. In inflammatory conditions, enhancement is not always diffuse, as expected, but may be focal. Spontaneous hemorrhages can account for labyrinth enhancement. In neoplastic conditions, enhancement may persist for as many as 6 months, and a mass effect against labyrinthine fluids may appear on GRASS images. Although there are no reports on labyrinthine degeneration after radiation therapy, one of our patients submitted to irradiation 7 years previously, had focal bilateral cochlear enhancement, which suggested a correlation with previous treatment.
Capillary Permeability↗
[Giving up life in the labyrinth].
A brief historic survey of the labyrinth, from prehistoric images carved in stone, to gardens, Renaissance drawings and architectonic constructions will presented. The metaphor of the labyrinths, which began with Theseus killing the Minotaur with the help of Ariadne, can be applied to all: scientific investigation, artistic creation, wickedness, theology ... to life. In these eculiar and chaotic designs, structural simplicity and functional complexity coincide and therefore may produce repeated erroneous decisions. To wander successfully through these labyrinths, caution and repeated decision-makings are required to enable the traveller to reach the desired and elusive center. In each instant, decisions are made in our mind as a consequence of complex cerebral systems, activated by stimuli which originate in the intimate regions of the mind, the most complex labyrinth of all. These types of mental labyrinths are immaterial, without paths or walks, where each successive decision made facing multiple bifurcations, causes the mental traveller to advance until reaching the center. This center deceptively becomes the entrance to another of the innumerable and unknown mental labyrinths that the intimate life proposes.
Brain↗
Responses of forelimb extensors to sinusoidal stimulation of macular labyrinth and neck receptors.
In precollicular decerebrate cats the multiunit EMG activity was recorded from forelimb extensors (triceps brachii) during isolated or combined sinusoidal stimulation of labyrinth and neck receptors at frequencies of 0.026--0.15 Hz. As expected from previous work, the first harmonic component of the EMG responses to roll tilt of the animal leading to selective stimulation of labyrinth receptors was characterized by an increased activity during side-down tilt and a decreased activity during side-up tilt (labyrinth responses); on the other hand just the opposite changes were elicited for the same directions of neck rotation (neck responses). For the peak amplitude of displacement of 10 degrees, the responses were always related to position and not to velocity of displacement. In some experiments in which the sensitivity of the neck responses was usually comparable to that of the labyrinth responses and the corresponding peaks were almost 180 degrees out of phase, a cancellation of the responses occurred during head rotation, leading to costimulation of labyrinth and neck receptors. In other experiments, however, in which the sensitivity of the neck responses was higher than that of the labyrinth responses, the forelimb extensors responded to head rotation in a fashion predictable from the vectorial summation of the responses obtained from separate macular and neck stimulation.
Animals↗