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PubMed2026

Cochlear size variation in a large-scale international multicentre cohort.

AIM: This study aims to (1) review the literature on cochlear size, measured by the A-value, to assess reported variation across studies, and (2) consolidate cochlear parameters-specifically basal turn diameter (A-value) and width (B-value)-measured using the standardized DICOM viewer OTOPLAN®, and compare these with published data. METHODS: A scoping literature review was conducted using the search term "diameter of cochlear basal turn" to identify studies reporting A-value measurements. To complement this, cochlear measurements obtained with OTOPLAN® were collected from clinical collaborators across multiple international centres. The ratio of B- to A-values, which defines the cochlear basal turn shape, was calculated as previously described by Khurayzi et al. (2021). RESULTS: The literature review identified 38 studies comprising 5,206 A-value measurements (average: 9.08 mm; range: 8.01-10.03 mm). Additionally, 5,580 OTOPLAN® measurements were collected from 43 clinics across 25 countries (mean: 9.07 mm; range: 6.67-11.45 mm). Overall, 68.7% of cochleae exhibited an elliptical basal turn shape. CONCLUSION: Using a large, international multicentre dataset and a standardized measurement tool, this study demonstrates substantial variation in cochlear size and shape across clinical cohorts from different regions. The mean A-value (9.07 mm) is consistent with previously published literature, while the wider observed range highlights greater anatomical variability within a multicentre clinical population than previously reported. The majority of cochleae demonstrate an elliptical basal turn configuration.

Humans↗
PubMed2006

Role of Gbx2 and Otx2 in the formation of cochlear ganglion and endolymphatic duct.

The boundary of gene expression of transcription factors often plays a role in making a signaling center in development. In the otic vesicle, Gbx2 is expressed in the dorso-medial region including the endolymphatic duct, and Otx2 in the ventral region. Fgf10 is expressed between their expression boundaries, and the cochleovestibular ganglion develops close to the medial side of the Fgf10 expressing domain. Similar expression patterns are observed in the central nervous system, where Otx2 and Gbx2 expression abut at the mid-hindbrain boundary, and the repressive interaction between Otx2 and Gbx2 defines the mid-hindbrain boundary. These analogous expression patterns raise a question about the role of the interaction between Gbx2 and Otx2 in the otic vesicle. To address this, we misexpressed Gbx2 and Otx2 to the otic epithelium. Ectopic Gbx2 expression could repress Otx2 expression and vice versa. In addition, Fgf10 expression was repressed and cochlear ganglion formation was interfered with. Moreover, endolymphatic duct was severely hypomorphic in the Otx2 misexpressing embryos. These results suggest that the interaction between Gbx2 and Otx2 in developing inner ear defines Fgf10 expression domain to induce the cochlear ganglion. It is also suggested that Gbx2 expression is important for the formation of the endolymphatic duct.

Animals↗
PubMed1994

Time course of endolymph volume increase in experimental hydrops measured in vivo with an ionic volume marker.

A new method has been developed to measure the cross-sectional area (CSA) of scala media in the living cochlea. The method has some advantages over histological methods, in which tissues may shrink or move during processing. In the present study, scala media CSA was measured in the second turn of guinea-pig cochleas in which endolymphatic hydrops was induced surgically. The area measurement method used an iontophoretic injection of a volume marker into scala media, during which the concentration of marker in endolymph was monitored with an ion-selective microelectrode. The measured marker concentration was inversely proportional to the CSA of endolymph. The marker we used was the anion arsenic hexafluoride (AsF6-), which was almost ideal for the purpose as it was retained well in endolymph. Area was measured in normal animals and in hydropic animals at times from 4 days to 16 weeks after endolymphatic duct obstruction. The results showed that hydrops develops within days of ablation of the endolymphatic duct. The degree of hydrops was compared with electrophysiological measures of function, including the endocochlear potential, action potential thresholds and the amplitudes of the cochlear microphonic, summating potential and action potentials. In the initial stages of hydrops development, electrophysiological changes were small. In contrast, there were marked functional changes between 8 and 16 weeks, when endolymph volume was no longer increasing. If the same is true for dysfunction in the ears of patients with Ménière's Disease, then it may not be possible to restore normal function simply by alleviating the hydrops.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1986

Experimental endolymphatic hydrops in the rat.

In the rat, the epithelial lining of the endolymphatic duct and sac, and the contents of the sac, showed remarkable differences in comparison with these structures in the guinea pig and man. Obliteration of the endolymphatic duct resulted in endolymphatic hydrops of varying severity in 55% of the rats, after survival times varying from one to five months. The presence of a positive periodic acid-Schiff-stain for coagulum accumulating in the endolymphatic duct after prolonged saccus obliteration suggests active involvement of the endolymphatic duct in the migration of endolymph toward the endolymphatic sac.

Animals↗
PubMedDate not supplied

Mondini's deafness. A review of histopathology.

From a histopathological survey of 12 ears (7 cases) of Mondini's deformity and deafness, the following conclusions or interpretations are drawn: 1) Mondini's bony deformity diagnosable by polytomography does not necessarily indicate Mondini's deafness or x-ray diagnosis of Mondini's deafness cannot be specifically relied upon. 2) The pars superior (semicircular canals and utricle) may be absent (aplastic) or the canals may be enlarged leading to interesting questions regarding vestibular physiology in such patients. 3) Enlarged endolymphatic duct and deficient utriculoendolymphatic valve are commonly found associated with absence of endolymphatic hydrops or collapse suggesting an operational longitudinal flow. 4) One and one-half or fewer (instead of 2 1/2) cochlear turns are characteristic; however, end-organ of Corti lesions (aplasia) may be present or absent leading to interesting speculations for further research regarding auditory function, especially in those cases with normal-appearing sensory structures. 5) Mechanisms of hearing loss in Mondini's deafness can be variably explained on the basis of inner ear or middle ear pathology including dysgenesis of the end-organs and associated neural elements sufficient to cause sensorineural hearing loss, aplasia of the oval or round windows which might explain manifest "sensorineural hearing loss" in the presence of normal-appearing organs of Corti and aplasia or infection of the middle ear causing a conductive loss which can be superimposed upon a sensorineural hearing loss.

Aged↗
PubMed1987

Hydrostatic pressure measurements of endolymph and perilymph in a guinea pig model of endolymphatic hydrops.

The primary histologic correlate of Menière's disease is endolymphatic hydrops. From this, many investigators have postulated the existence of endolymphatic hypertension, although there have been no measurements published to substantiate this concept. Seventy guinea pigs, surgically treated with right endolymphatic duct obstruction, were later assessed by use of a micro-electrode technique that measured their endolabyrinthine hydrostatic pressures. For 21 of these animals, the pressures of both scala tympani (Pst) and scala media (Psm) of both ears of each animal were successfully measured. Similar measurements were made in a control group of 25 guinea pigs that had not undergone any previous surgery. For normal ears--as well as those with hydrops-pressure differences between perilymph and endolymph (Psm - Pst) varied around 0 +/- 2.0 mm Hg. When only the right (obstructed) ears were considered, there appeared to be a slight, relative pressure elevation (p less than 0.05) in scala media during the first 7 days after endolymphatic duct obstruction-and in those ears with EP, less than 70 mV. The magnitude of this pressure difference that can be attributed to the state of endolymphatic hydrops-and not to natural variability-is calculated (within 95% confidence limits) to be less than 0.5 mm Hg.

Animals↗
PubMed1986

Comparative morphometric study of the vestibular system of the vertebrata: reptilia, aves, amphibia, and pisces.

Morphometric measurements were made from serial sections of the vestibular system in four classes of vertebrates: Reptilia, Aves, Amphibia, and Pisces. Representative species of reptile studied were the lizard (Gekko gecko), the common garter snake (Thamnophis sp.), and the common turtle (Chelonia sp.). The budgie (Melopsittacus undulatas), the common pigeon (Columba domestica), the yellow-bellied sapsucker (Sphyrapicus varius), and the horned owl (Bubo virginianus) were chosen as representative of the bird. For the amphibian, the leopard frog (Rana pipiens), and the mud puppy (Necturus maculatus) were chosen for study. As representative of the fish, the goldfish (Carassius auratus), the tilapia (Tilapia mossambica), the guppy (Lebistes sp.), and the sea horse (Hippocampus sp.) were used in these measurements. The morphometric data obtained were then used in estimates of the time constants in the Steinhausen equation which describes the biophysics of fluid flow in the semicircular canals. In general, the time constants (theta/II in the Steinhausen equation) of these representatives of Reptilia, Aves, and Amphibia were of magnitude similar to those reported in mammals, despite the dissimilarities in the diameters of the ducts, the duct radii of curvature, the dimensions of the cristae ampullares and the utricle, and volumes of endolymph within the vestibular system. However, the short-time constants in Pisces were larger (therefore providing a slower response) than those in other vertebrates, and were similar to that of the turtle and the mud puppy.

Amphibians↗
PubMed1993

Symptomatic versus asymptomatic endolymphatic hydrops: a histopathologic comparison.

One of the unanswered questions in Meniere's disease research is the pathophysiology by which the classic symptoms are produced. A histopathological study was undertaken to identify the pathological features of symptomatic endolymphatic hydrops and their relationship to these symptoms. Two groups of temporal bones were examined, compared, and described. The first group was from patients with symptoms of Meniere's disease (n = 29). Temporal bones in the second group were chosen for the presence of endolymphatic hydrops and the absence of otologic symptoms (n = 13). Significant differences were noted in the severity of hydrops, the frequency of membrane ruptures, the endolymphatic duct, and coexistent pathologic conditions. Ruptures were seen in 38% of temporal bones from symptomatic patients and in only 8% of temporal bones from patients with asymptomatic endolymphatic hydrops. Based on this study and a review of the literature, the authors believe that the symptoms and findings of Meniere's disease are explained best on the basis of both chemical and physical mechanisms being operational intermittently and together.

Cochlea↗
PubMed1991

The effect of glycerol on short-term experimental endolymphatic hydrops.

The aim of this paper was to evaluate the effect of one month of treatment with different dosages of glycerol on experimental endolymphatic hydrops produced by obliteration of endolymphatic sac and duct through an extradural approach. Forty-two guinea pigs were used. The animals, divided into six groups, received 0.5-2 gr/kg body weight of the drug per day for one month. The activity of glycerol was determined by statistical analysis of volumetric changes of scala media. Glycerol demonstrated the effect of reducing endolymphatic hydrops. The decrease in hydrops was influenced by the dosage suggesting a stria metabolic response.

Administration, Oral↗
PubMed1991

The effect of glycerol on the guinea-pig hydropic ear.

The aim of this paper was to investigate the effect of glycerol on experimental endolymphatic hydrops in guinea-pigs. The right endolymphatic sac and duct were obliterated through an extradural posterior fossa approach. Some animals received a 3 g/kg dose of glycerol for a period of 7 days, whereas others received the same dose for 30 days. The activity of glycerol was studied by investigating the volumetric changes in the scala media determined with a computerized planimeter. Glycerol induced a significant reduction of the hydrops showing its effectiveness and suggesting a strial metabolic response.

Animals↗
PubMed1992

Tetramethylammonium for in vivo marking of the cross-sectional area of the scala media in the guinea pig cochlea.

A physiologic technique was developed to measure endolymphatic cross-sectional area in vivo using tetramethylammonium (TMA) as a volume marker. The technique was evaluated in guinea pigs as an animal model. In the method, the cochlea was exposed surgically and TMA was injected into endolymph of the second turn at a constant rate by iontophoresis. The concentration of TMA was monitored during and after the injection using ion-selective electrodes. Cross-section estimates derived from the TMA concentration measurements were compared in normal animals and animals in which endolymphatic hydrops had been induced by ablation of the endolymphatic duct and sac 8 weeks earlier. The method demonstrated a mean increase in cross-sectional area of 258% in the hydropic group. Individually measured area values were compared with action potential threshold shifts and the magnitude of the endocochlear potential (EP). Hydropic animals typically showed an increase in threshold to 2 kHz stimuli and a decrease in EP. However, the degree of threshold shift or EP decrease did not correlate well with the degree of hydrops present.

Animals↗
PubMedDate not supplied

Middle ear overpressure treatment of endolymphatic hydrops in guinea pigs.

Guinea pigs placed outside or inside a pressure chamber and exposed to 49.2 cm H2O overpressure continuously for 24 h immediately after blockage of the endolymphatic duct showed no significant difference in the magnitude of endolymphatic hydrops when compared to controls, although there was a slight indication of a volume decrease in the outside-treatment group and an increase in the inside-treatment group. A pressure increase of 49.2 cm H2O in the external auditory canal for 1 h twice a day for 2 weeks outside the chamber significantly inhibited the development of hydrops. The latter result supports the merit of pressure application through the external auditory canal as a treatment for Meniere's disease.

Analysis of Variance↗
PubMedDate not supplied

Effect of diuretics on endolymphatic hydrops.

The effect of diuretics on endolymphatic hydrops, which was produced by obliteration of the endolymphatic duct and sac in guinea pigs, was determined by statistical analysis of volumetric changes in the scala media. When acetazolamide was administered orally at 159 to 434 mg/kg per day for a period of 30 days, endolymphatic hydrops did not reach the extent of distension shown in animal ears without drug treatment. No difference was seen in animals with one month of drug treatment followed by three additional months without treatment. This result suggests that acetazolamide has the effect of reducing endolymphatic hydrops only during the period of drug administration. On the other hand, there appeared to be no effect, statistically, on hydrops in animals which were treated with chlorthalidone 72 to 182 mg/kg every other day for one month with survival times varying from one to four months. The effect of this drug favorably reported for the treatment of Meniere's disease symptoms is not demonstrated on endolymphatic hydrops, but rather is likely to involve other mechanisms. There was no essential difference in the extent of cochlear sensory and neural atrophy in the inner ears of animals with or without these drug treatments.

Acetazolamide↗
PubMed1999

Immunolocalization of Bone Morphogenetic Protein-2 and -3 and Osteogenic Protein-1 during murine tooth root morphogenesis and in other craniofacial structures.

The distribution of Bone Morphogenetic Protein-2, and -3 (BMP-2 and BMP-3) and Osteogenic Protein-1 (OP-1, also known as BMP-7) during root morphogenesis and in other craniofacial structures was examined in sections of 12- to 18-d-old mouse heads using polyclonal and monoclonal antibodies. BMP-3 and OP-1 were localized in alveolar bone, cementum, and periodontal ligament, whereas BMP-2 was only localized in the alveolar bone of periodontium. All three BMPs were localized in predentine, dentine, odontoblasts, osteoblasts, osteocytes, osteoid, cartilage, chondrocytes and spiral limbus. BMP-2 and OP-1 were also localized in spiral ligament and interdentate cells of the cochlea, whilst BMP-3 was restricted to the spiral ganglion. BMP-3 was also localized in ducts of submandibular and sublingual salivary glands, acini of the lacrimal gland, Purkinje cells in the cerebellum, nerve fibres of the cerebellum and brain, afferent cells of the dorsal root ganglia, inferior alveolar nerve, and peripheral processes of the vestibulocochlear nerve. OP-1 was also localized in hair and whisker follicles, sclera of the eye and in ameloblasts. The demonstration of BMP-3 in the nervous system suggests that this protein may be neurotrophic during development and maintenance of the nervous system. The composite expression of BMPs/OPs during periodontal tissue morphogenesis suggests that optimal therapeutic regeneration may entail the combined use of different BMPs/OPs.

Afferent Pathways↗
PubMed2003

Correlation between hearing loss and scala media area in guinea pigs with long-standing endolymphatic hydrops.

HYPOTHESIS: Histologic analysis of the hydropic and normal guinea pig cochleae was undertaken to assess a potential correlation between the magnitude of endolymphatic hydrops and hearing loss. It was hypothesized that a greater correlation than previously reported might be found by looking at long-standing endolymphatic hydrops and high-frequency range hearing. BACKGROUND: Surgically induced endolymphatic hydrops in guinea pigs is the most widely used animal model for the study of human Ménière's Disease and recapitulates both endolymphatic hydrops and progressive sensorineural hearing loss. A strong correlation between the magnitude of hydrops and severity of hearing loss has been reported in the human condition, but not in the animal model. METHODS: Nine albino guinea pigs were each subjected to surgical obstruction of the endolymphatic sac and duct of the right ear. The left ears remained as internal histologic controls. Hearing was assessed from 2 kHz to 32 kHz by auditory brain stem response testing for 16 to 25 weeks after surgery. Histologic morphometry after the animals were killed was used to quantify both turn-specific and weighted overall hydrops. These measures were correlated with hearing loss in each animal at all tested frequencies. RESULTS: A statistically significant correlation between the magnitude of hydrops and the severity of hearing loss was observed for 2 kHz and 16 kHz. These frequencies correlated with both turn-specific hydrops and overall hydrops. However, turn-specific hydrops did not reliably correlate with the magnitude of hearing loss at anatomically appropriate frequency ranges. Where such a correlation did exist, it might well have been simply part of an expression of an overall correlation between hydrops and hearing loss. CONCLUSIONS: There may be a greater correlation between hydrops and hearing loss in guinea pigs with long-standing surgically induced hydrops than has previously been reported in animals with less advanced disease. These findings help to validate continued use of the model for hearing loss related to Ménière's Disease, verify the rationale of treatment modalities aimed at reducing hydrops in the human condition, and may indicate that efforts at reducing hydrops in such patients has benefits toward long-term hearing preservation.

Animals↗