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Results for “Endolymphatic Hydrops”

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PubMed1995

Modulation of inner ear pressure in experimental endolymphatic hydrops.

Physiologic study of the guinea pig model of endolymphatic hydrops has been used to better understand the manifestations of Meniere's disease. Quantitative vestibular function testing demonstrates some changes in the hydrops subjects, especially if an additional stress such as postural inversion is imposed. Understanding the hydrodynamic changes on the endolymphatic and perilymphatic fluids by the hydrops condition as well as postural inversion may be useful in explaining the vestibular findings. These pressure effects may alter the micromechanics of the inner ear or possibly induce a relative vascular ischemia. Auditory dysfunction is speculated to occur through similar mechanisms.

Animals↗

PubMed1991

Apparent travelling wave velocity changes in cases of endolymphatic hydrops.

This study attempted to develop a test which would be specific for endolymphatic hydrops. It is based upon the hypothesis that increased pressure in the scala media will alter the stiffness of the basilar membrane and hence increase the speed of the travelling wave. Auditory brainstem-derived responses were used to measure the basilar membrane travelling wave velocity in normals and to take the equivalent measures in Meniere's patients. Ten normally hearing subjects and 20 Meniere's patients were tested. The data for the Meniere's group showed that the travelling wave velocities were within normal limits at all frequencies tested, except 5.7 kHz where the travelling wave velocity greatly exceeded that of the normal group. A theoretical possibility that these findings may be the result of damaged and broadened VIIIth nerve tuning curves is discussed but travelling wave measures and psychophysical tuning curve measurements on the Meniere's group, normals and noise-induced hearing loss (NIHL) cases showed that this was not a significant factor. The data indicate that this technique can detect endolymphatic hydrops and a short duration clinical procedure has been devised.

Adolescent↗

PubMed2003

Changes in CAP adaptation in experimentally induced endolymphatic hydrops.

OBJECTIVE: To determine the effect of experimentally induced endolymphatic hydrops (ELHs) on compound action potential (CAP) adaptation. METHODS: The CAP was recorded 1 month after surgical treatment to produce ELH. The CAP threshold in response to click stimuli showed no significant differences between the hydropic and control groups. The CAP was elicited from the retroauricular-exposed round window using a silver ball electrode. Click trains consisting of 10 clicks with an interclick interval (Deltat) of either 4 or 8 ms were delivered through a loudspeaker placed in front of the animals' ears. The patterns of adaptation to these click trains were evaluated as functions of Deltat and intensity level. RESULTS: An abnormal pattern of CAP adaptation was observed in hydropic ears. CONCLUSIONS: These findings suggest that early ELH influences CAP adaptation.

Acoustic Stimulation↗

PubMed1980

Apical lesions of the cochlea in idiopathic endolymphatic hydrops and other disorders: pathophysiological implications.

Apical lesions of the cochlea may be caused by direct trauma, impairment of blood supply, contamination of perilymphatic fluid and endolymphatic hydrops. It is proposed that endolymphatic hydrops causes apical lesions when endolymph or its components leak into the perilymphatic fluid and pass through the helicotrema to degrade the tissue fluid environment of the sensory and neural structures in this area.

Aged↗

PubMed1993

Reduced Na(+)-K(+)-ATPase activities in the cochleae of guinea pigs with experimental endolymphatic hydrops.

Normal auditory function depends on the maintenance of the unique ion composition in the endolymph. The Na(+)-K(+)-ATPase in the lateral wall of the cochlear duct has been suggested to play an important role in maintaining the endolymphatic ion concentration and in generating a positive endocochlear potential. Cochlear dysfunction may indicate changes in the biochemical components and osmotic pressure of the inner ear fluids as well as inadequate generation of intracellular metabolic energy. Dysfunction of the stria vascularis and spiral prominence was investigated in the early stages of endolymphatic hydrops. Vibratome sections of hydropic and normal cochleae were stained histochemically for Na(+)-K(+)-ATPase activity in this study. Decreased activity of this enzyme was shown in the stria vascularis and spiral prominence of the hydropic cochlea in the early stage of endolymphatic hydrops. The results coincide with those of studies of electrophysiologic changes in cochlear function in hydropic animals by others. The results of the present study provide further information concerning a possible deficit in ion transport activity and decreased enzymatic activity in the cochlea.

Animals↗

PubMed2005

The basic science of Meniere's disease and endolymphatic hydrops.

PURPOSE OF REVIEW: Meniere's disease is characterized by the triad of fluctuating hearing loss, episodic vertigo, and tinnitus and by endolymphatic hydrops found on post-mortem examination. The cause of Meniere's disease remains unclear. Numerous factors play a role in the development of hydrops and in the pathogenesis of related cochleovestibular dysfunction. This review highlights recent advances in the understanding of the pathophysiology of symptom development in Meniere's disease by detailing the role of genetics, autoimmunity, endolymphatic fluid homeostasis, excitotoxicity, oxidative stress, and cellular apoptosis. Emphasis is placed on reviewing the newly described animal models that exhibit endolymphatic hydrops. RECENT FINDINGS: Recent evidence suggests that hearing loss might be explained in part by apoptosis of spiral ganglion neurons and that hydrops could represent an epiphenomenon rather than an initiating factor. In addition, the accepted guinea pig model described by Kimura has certain limitations. An animal model that would supplement and in some cases replace the surgically induced model is currently being sought. SUMMARY: These recent advances have expanded our understanding and will allow for the development of targeted therapeutic interventions aimed at preventing the progression oochleovestibular deterioration.

Animals↗

PubMedDate not supplied

Functional and morphological changes in experimental endolymphatic hydrops.

Electrocochleograms (ECochG) in response to tone bursts and electronystagmograms (ENG) during sinusoidal rotational stimulation were monitored in guinea pigs equipped with chronically implanted round-window and periocular electrodes before and for as long as 90 days after uni- or bilateral surgical obliteration of the endolymphatic duct. The presence of cochlear and saccular endolymphatic hydrops was verified during microdissection of the inner ear, and cochlear hair cell counts were performed in some of the animals. The results indicate that in surgically-induced endolymphatic hydrops, cochlear and vestibular changes occur similar to those observed clinically in Menière's disease: fluctuant threshold shifts, threshold elevation at low frequencies, sensorineural loss at all frequencies with recruitment, increase in the ratio of summating potential to compound action potential (SP/CAP), asymmetry and recruitment in the ENG, and increased vestibular excitability, with occasional post-rotational and spontaneous nystagmus. Functional changes could not be clearly correlated with those seen by light microscopy, since hair cell loss was confined mainly to the apical coil. The observations indicate that the guinea pig with surgically-induced endolymphatic hydrops can be a useful model of Menière's disease, not only on morphological grounds, but also on the basis of functional changes, which over the relatively short term of observation represent a dysfunction rather than a loss of sensorineural structures.

Animals↗

PubMed1990

Bilateral endolymphatic hydrops in Menière's disease: review of temporal bone autopsies.

The wide range in incidence rates reported for bilateral Meniere's disease results mainly from the lack of established clinical criteria for bilaterality, and from follow-ups of varying duration. In order to help determine a reasonable bilateral involvement rate, we examined histologic reports of temporal bones with endolymphatic hydrops. We reviewed the literature on temporal bone autopsies from 1938 to 1988, and selected 72 cases for histologic examination. Of the 72 cases, 67 (93%) showed endolymphatic hydrops, 2 (2.8%) showed collapse, and 3 (4.2%) showed membranous labyrinths of normal appearance. Twenty of the 67 endolymphatic hydrops cases (29.9%) displayed bilateral involvement, suggesting a rate of bilaterality in Meniere's disease of approximately 30%.

Edema↗

PubMed1991

Blockage of longitudinal flow in endolymphatic hydrops.

The external shunt operation on the endolymphatic sac is based on the concept that it will drain excess endolymph and thus arrest the progression of endolymphatic hydrops. We performed histological studies on 46 temporal bones from 13 cases of bilateral and 20 cases of unilateral Meniere's disease to evaluate the status of the pathways of longitudinal flow of endolymph to the sac. The endolymphatic ducts were blocked in 8 specimens (17%), the endolymphatic sinuses in 9 (19.5%), the utricular ducts in 12 (26%), the saccular ducts in 7 (15%), and the ductus reuniens in 27 (59%). These blockages arrested longitudinal flow from both the pars superior and inferior in 21 cases (46%), the pars superior only in 3 (6.5%), and the pars inferior only in 16 (35%). In the 6 ears with all pathways open, 2 were found to have fistulae between the saccules and the perilymphatic spaces, which theoretically results in internal shunting, thus alleviating the need for the external shunt procedure. In the aggregate, therefore, 42 (91%) of 46 ears showed either areas of blockage of longitudinal flow or internal shunts that would theoretically negate the value of external endolymphatic shunt procedures. These temporal bones, however, are from an autopsy population and the severity of pathological changes is probably greater than it would have been at an earlier age when external shunt surgery might have been a therapeutic consideration.

Adult↗

PubMedDate not supplied

Saccular and cochlear endolymphatic potentials in experimentally induced endolymphatic hydrops of guinea pigs.

Saccular and cochlear endolymphatic potentials (SEP and CEP) were recorded in 33 normal animals. We confirmed that SEP is not produced in the saccule per se, but is a potential leak from the cochlea. CEP was reduced to one-tenth of the original value when it reached the saccule. Endolymphatic hydrops was provoked in 32 animals, and CEP and SEP were successfully recorded in 29 and 20 cases, respectively. The measurements were performed in the 2nd, 4th and 12th postoperative week. Both CEP and SEP decreased in magnitude as time elapsed after the surgery. This reduction is attributed to the strial dysfunction. In advanced hydrops, CEP transmission to the saccule is greatly inhibited. It is concluded that the saccular dysfunction can occur in the hydropic ear.

Animals↗

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↗

PubMed1993

Immunological pathogenesis of endolymphatic hydrops and its relation to Menière's disease.

This study was designed to investigate an immunologically induced endolymphatic hydrops (ELH) and to focus on the issue of its pathogenesis in relation to Menière's disease. The time course of ELH was evaluated by light microscopy in a 2-hour to 7-month period following direct antigen challenge to the endolymphatic sac (ELS) in systemically pre-sensitized guinea pigs. ELH began to appear in the vestibule and the basal turn 5-7 hours after inner ear challenge and developed gradually. During the interval from the second day to the first week, ELH rapidly developed in all the cochlear turns and reached a maximum size. During the period from the second week to the eighth week, ELH gradually reduced. After 9 weeks, ELH of the saccule and the cochlea gradually recurred. During the interval from the first week to the eighth week, the time course of ELH correlated well with the grade of cellular infiltration of the perisaccular tissue. These results suggest that recurrent immunological reaction in the ELS may result in disorders of the ELS which finally lead to the onset of Menière's disease.

Animals↗

PubMed2002

Perilymphatic and endolymphatic pressures during endolymphatic hydrops.

We analysed the fluid pressure in the perilymphatic and endolymphatic spaces of the cochlea in eight guinea pigs after endolymphatic hydrops (EH) was surgically created. The control experiments were done in the opposite ears. EH was histologically confirmed after the conclusion of the pressure measurements. No statistically significant pressure difference between the scala media and the scala tympani was found, either in ears with EH or the control ears. However, the endocochlear potential, which we evaluated for position verification of the measurement pipette in the cochlea, was statistically significantly decreased in ears with EH.

Animals↗

PubMed1976

Endolymphatic hydrops: mechanical causes of hearing loss.

An explanation for the mechanical origin of the hearing loss in endolymphatic hydrops is presented that is based on studies in mechanical cochlear models. An elastic bias of the basilar membrane and/or a mass loading of the cochlear duct account for the low-frequency hearing loss, diplacusis, and even-harmonic distortion. In addition, the static shearing displacement between the tectorial membrane and the organ of Corti, caused by the displacement of the basilar membrane, may partially decouple the hair cells from the tectorial membrane, an event that would explain the tinnitus, recruitment, and perhaps even the disportional loss of speech intelligibility associated with endolymphatic hydrops.

Basilar Membrane↗

PubMed1995

Effect of endolymphatic hydrops on capsaicin-evoked increase in cochlear blood flow.

Capsaicin, which causes release of neuropeptides including substance P, has been shown to cause dose-related increases in cochlear blood flow (CBF). Since CBF regulation is altered in animal models with endolymphatic hydrops, this study was designed to examine the effect of hydrops on capsaicin-induced CBF changes. CBF responses to 0.01 and 0.001% capsaicin applied to the round window membrane were measured in normal and 12-week hydropic guinea pigs using laser Doppler flowmetry. With 0.01% capsaicin, CBF increased by only 13 +/- 7.8% in the hydropic ear, compared with 34% +/- 13% in the normal animal (p = 0.027). With 0.001% capsaicin, CBF increased by only 7.5 +/- 4.2% in the hydropic ear, compared with 28 +/- 16% in the normal ear (p < 0.001). These findings demonstrate a reduced responsiveness to capsaicin with endolymphatic hydrops and suggest that hydrops causes an alteration in the peptidergic sensory fibers of the inner ear or in the vascular smooth muscle or both. The results are consistent with previous reports of reduced vascular responsiveness in hydropic guinea pigs and provide further evidence for abnormal CBF regulation in hydrops.

Alkaloids↗

PubMed1994

Electrocochleography in experimental endolymphatic hydrops.

This study investigated whether dominant negative summating potential (DNSP) is absent at all stages of induced hydrops development, including the early stages of hydrops formations. Electrocochleography (ECoG) was done 3 days to 20 weeks after obliteration of the endolymphatic sac in guinea pigs, by electrodes attached to the cochlear bony wall on the scala vestibuli of the basal turn. DNSP was noticed only during the early stages of endolymphatic hydrops formation, before hydrops was fully developed. There was no DNSP when the distension of Reissner's membrane was marked. Increased endolymphatic pressure and/or changes in biochemical composition were thought to be the causes of DNSP.

Action Potentials↗

PubMed2003

The effects of V2 antagonist (OPC-31260) on endolymphatic hydrops.

In the present study, two experiments were performed to investigate the influence of OPC-31260 on experimentally induced endolymphatic hydrops in guinea pigs and the regulation of aquaporin-2 (AQP2) mRNA expression in the rat inner ear. In morphological studies, the increases in the ratios of the length of Reissner's membrane (IR-L) and the cross-sectional area of the scala media (IR-S) were quantitatively assessed among normal guinea pigs (normal ears) and three groups with hydropic ears: hydropic ears with no infusion (non-infusion hydropic ears), hydropic ears with an infusion of physiological saline into the scala tympani (saline-infused hydropic ears) and hydropic ears with infusion of 0.3% OPC-31260 into the scala tympani (OPC-infused hydropic ears). IR-Ls in the experimental groups were markedly larger than in the normal ear group, but there was no significant difference among the groups of non-infusion hydropic ears, saline-infused hydropic ears and OPC-infused hydropic ears. The IR-Ss of non-infusion hydropic ears and saline-infused hydropic ears (48.8-49.3%) were statistically different from that of normal ears (6.5%) (Dunnet multiple comparison test, P<0.01). However, IR-S of the OPC-infused hydropic ears (-14.8%) was significantly smaller than those of non-infusion hydropic ears and saline-infused hydropic ears (one-way ANOVA, P<0.01). In the quantitative polymerase chain reaction study, a comparison of the ratio of AQP2 and beta-actin mRNA (MAQP2/Mbeta-actin) was made between water-injected and OPC-31260-injected rats. An intravenous injection of OPC-31260 resulted in a significant decrease in MAQP2/Mbeta-actin both in the cochlea and in the endolymphatic sac (t-test, P<0.001). These results indicate that water homeostasis in the inner ear is regulated via the vasopressin-AQP2 system, and that the vasopressin type-2 antagonist OPC-31260 is a promising drug in the treatment of Meniere's disease.

Analysis of Variance↗

PubMed2001

Delayed endolymphatic hydrops: study and review of clinical implications and surgical treatment.

Delayed endolymphatic hydrops (DEH) differs from Ménière's disease in that it occurs in pre-existing ear pathology in patients who have a profound unilateral or total deafness that was caused by infection, trauma, or unknown causes during childhood or adulthood. We performed a retrospective review of 160 patients with ipsilateral, contralateral, or bilateral DEH. Eighty-seven patients who did not respond to medical therapy underwent surgical treatment. Our findings indicate that the more conservative surgical procedures--endolymphatic sac surgery, cochleosacculotomy, and streptomycin perfusion--are all as effective as and less destructive than labyrinthectomy for controlling vertigo. The clinical results of this study would seem to support the observations of others that DEH and Ménière's disease are related disorders caused predominantly by cases of viral labyrinthitis with unknown etiology.

Adult↗