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PubMed1986

Effects of lesion of the interstitial nucleus of Cajal on vestibular nuclear neurons activated by vertical vestibular stimulation.

Experiments were performed in cats anesthetized with nitrous oxide to study the effects of INC lesions on responses of vestibular nuclear neurons during sinusoidal rotations of the head in the vertical (pitch) plane. Responses of neurons in the INC region were recorded during pitch rotations at 0.15 Hz. A great majority of these neurons did not respond to static pitch tilts, and they seemed to respond either to anterior or to posterior semicircular canal inputs with a peak phase lag of 140 deg (re head acceleration). Responses of vestibular nuclei neurons in intact cats were recorded during pitch rotations at the same frequency (0.15 Hz). Neurons that seemed to respond to vertical semicircular canal inputs showed peak phase lags of 90 deg relative to head acceleration, whereas neurons that responded to static pitch tilts showed peak phase shifts near 0 deg. These results indicate that responses of neurons in the INC region lag those of vestibular neurons by about 50 deg, suggesting that the former neurons possess a phase-lagging (i.e. integrated) vestibular signal. Responses of vestibular neurons in cats that had received electrolytic lesions of bilateral INCs 1-2 weeks previously were recorded during pitch rotations at the same frequency (0.15 Hz). Neurons that presumably responded to vertical semicircular canal inputs showed a peak phase lag of 60 deg relative to head acceleration, a significant decrease of the phase lag compared to normal, whereas responses near 0 deg were unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1963

Significance of vestibular organs in problems of weightlessness.

Two important questions concerning the organs of equilibrium are posed by orbital and space flights. The first is whether exposure to weightlessness may evoke symptoms of vestibular origin, and the second is how to prevent symptoms of vestibular origin should it be decided to abolish weightlessness by causing the spacecraft to spin. It is important to determine whether vestibular symptoms are to be ascribed to the otolith apparatus or to the semicircular canals, or to both. During exposure to weightlessness the usual gravitational stimulus to the otolith apparatus is lost, and this reduction in afferent input might be expected to disturb the integrative patterns in the central nervous system. All such disturbances are special instances of a common cause for the appearance of functional syndromes such as seasickness. If orbiting vehicles are caused to rotate in order to abolish weightlessness, the angular velocity will be determined by the effective radius of rotation and the rate of spin, i.e., how nearly it is desired to simulate 1 g. At very short radii the complicating effects of exposure of the body to variations in centripetal force must be considered. With longer radii the principal stress will arise as a result of constant rotation, which, in combination with head movements, generates Coriolis forces. These forces cause bizarre patterns of stimulation of the semicircular canals which in turn may result in illusions and "canal sickness". This type of motion sickness has its origin in the semicircular canals and deserves the term "canal sickness". The angular velocities which represent a negligible stress or a tolerable stress are defined. A brief description is given of illusory phenomena and other manifestations together with the time-course of the adaptive process.

Acceleration↗
PubMed1989

Sodium transfer from endolymph through a luminal amiloride-sensitive channel.

An in vitro preparation of frog semicircular canal was devised to study the mechanisms of Na transport across the labyrinthine epithelium. When the lumen of the semicircular canal was filled with perilymph-like solution, the structure was able to secrete K into and to absorb Na from the lumen and to generate a lumen-positive transepithelial potential. When the lumen of the semicircular canal was filled with endolymph-like solution, the electrochemical composition of the luminal fluid was partly maintained up to 2 h. In this last experimental condition net and unidirectional fluxes were calculated in absence or presence of transport inhibitors, separately for the ampulla and for the nonampullar part of the canal. Amiloride (10(-5) M) but not dimethyl amiloride (10(-5) M) inhibited 60% of the unidirectional Na efflux out of endolymph; this Na efflux decrease resulted in an increase of the inward net Na flux. The net Na flux was also increased after abluminal application of ouabain (10(-3) M), furosemide (10(-4) M), and bumetanide (10(-6) M). This study validates this isolated preparation as a suitable tool for the study of endolymph secretion, confirms that the secretion of endolymph is achieved in the ampulla, and provides evidence for an apical amiloride-sensitive Na channel through which Na is transferred out of endolymph along an electrochemical gradient provided by the activity of the abluminal Na+-K+-ATPase.

Amiloride↗
PubMed1986

Surgical management of labyrinthine fistula with cholesteatoma.

From 684 cases of ear surgery for cholesteatoma performed by one surgeon, 35 had labyrinthine fistulae (incidence 5.1 per cent). Of these fistulae, 79 per cent involved the lateral semicircular canal only; the other sites involved were the other semicircular canals and the cochlea. The fistula test was positive in 54 per cent of cases overall, but in 80 per cent with an extended site fistula (ESF). Three surgical approaches were employed sequentially--staged combined approach tympanoplasty (CAT), open cavity tympanoplasty and attico-antrotomy. Surgically-induced deafness occurred in 3.3 per cent. All surgical groups showed similar hearing results, except for less conductive deafness in the CAT group. Surgical management is discussed with reference to current theories of the erosive effects of cholesteatoma.

Adolescent↗
PubMed2003

Establishment of normative cochlear and vestibular measurements to aid in the diagnosis of inner ear malformations.

OBJECTIVE: We sought to establish normative measurements of the inner ear using computed tomography (CT) of the temporal bone to aid in the diagnosis of inner ear malformations. STUDY DESIGN AND SETTING: Prospective measurements of the inner ear structures were made on axial and coronal temporal bone CT scans on 15 patients with normal hearing and 15 patients with sensorineural hearing loss. RESULTS: The vertical height of the cochlea on coronal scan and the size of the central bony island within the lateral semicircular canal on axial scan along with visual inspection identified 7 inner ear abnormalities in 6 patients: 5 cases of lateral semicircular canal dysplasia and 2 cases of cochlear hypoplasia. In contrast, visual inspection alone identified only 4 of the 7 abnormalities. CONCLUSIONS AND SIGNIFICANCE: Routine measurement of the cochlear height and bony island of the lateral semicircular canal, in conjunction with visual inspection of CT images, will increase recognition of common inner ear malformations.

Adult↗
PubMed1978

Vestibular-optokinetic interactions in normal subjects and in patients with peripheral vestibular dysfunction.

The vestibulo-ocular reflex (VOR) during rotation, optokinetic nystagmus (OKN), and interactions between the vestibulo-ocular and optokinetic systems were studied quantitatively in 10 normal human subjects, 15 patients with unilateral horizontal semicircular canal paralysis (UP), and 11 patients with bilateral horizontal semicircular canal paralysis (BP). The OKN gain (eye velocity/drum velocity) was not significantly different between the normal subjects and the patient groups. During tests in which rotatory and visual stimuli were presented simultaneously, the contribution to the observed eye movements by the VOR was only one-fourth to one-third of its gain during rotation in the dark in the normal subjects and UP patients. These interactive tests did not differentiate UP patients from normal subjects but did separate BP patients from normal subjects.

Adult↗
PubMed1987

Adenosine is a modulator of hair cell-afferent neurotransmission.

Adenosine has been implicated in neuromodulation in the central nervous system [(1985) Annu. Rev. Neurosci. 8, 103-124]. Its mechanism of action is thought to be a receptor-mediated inhibition of a transmitter release. To assess adenosine's role as a neuromodulator in the vestibular periphery, spontaneous activity of the afferent fibers in the ampullar nerve of the semicircular canal, in vitro, was used as the dependent variable. Afferent firing has been previously shown to depend on transmitter release by the hair cells [(1985) Brain Res. 330, 1-9]. Adenosine was shown to inhibit firing rate; the adenosine antagonist theophylline was shown to increase firing rate; the enzyme adenosine deaminase, which catabolizes adenosine to inosine, was shown to increase firing rate; the adenosine uptake inhibitor dipyridamole was shown to decrease firing rate; and adenosine was shown to be released from the isolated semicircular canal by electrical stimulation. All these findings are internally consistent and unreservedly support the hypothesis that adenosine has a neuromodulatory role in neurotransmission in the semicircular canal.

Adenosine↗
PubMed1981

Fetal ear malformations induced by maternal ingestion of thalidomide in the bonnet monkey (Macaca radiata).

Gross malformations of the external, middle, and internal ear were seen in fetal monkeys following maternal ingestion of thalidomide. Twenty-five pregnant bonnet monkeys (Macaca radiata) were each given a single oral dose of 10 mg/kg of thalidomide on day 24, 25, 26, 27, 28, or 29, or 30 mg/kg on day 25 or 28 of gestation. (Day of mating is assumed to be day zero of pregnancy). The skeletons, processed and stained with Alizarin Red S, were examined for changes in configuration and/or ossification of the ossicles and temporal bones. Bilateral temporal bones of one case, treated on day 24, were sectioned at 10 microns and examined histologically. Twelve fetuses collected at 70 +/- 3 days of gestation showed no gross ear defects, while 10 out of 13 fetuses collected at 100 +/- 3 days of gestation had structural anomalies similar to those observed in humans. All malformations were severe in fetuses treated on day 24 of gestation and lessened in degree of severity with treatments on days 25-28. Fetuses treated on day 29 were normal. External ear anomalies included microtia with meatal atresia or stenosis, and varying degrees of auricular hypoplasia. Defects of the middle ear were predominantly hypoplasia of malleus, incus, and tympanic ring. Fused ossicles and cochlear and vestibular window abnormalities were only seen in animals treated on day 24. The internal ear exhibited petrosal hypoplasia and delayed ossification of the lateral aspect of the lateral and posterior semicircular canals. Cochlear, vestibular, semicircular, and transcapsular canal defects were confirmed histologically in one case.

Abnormalities, Drug-Induced↗
PubMed2001

[Treatment of labyrinthine fistulas in chronic otitis media].

Labyrinthine fistulas (l.f.) are reported to be diagnosed in 3-12.9% of the chronic otitis media patients. Their most frequent location is the lateral semicircular canal. The other locations include posterior semicircular canal, superior s.c. and vestibular window. Surgical removal of the cholesteatoma matrix brings a high risk of the complete hearing loss in the operated ear. Preoperative diagnosis of the l.f. is not always possible. Authors present the analysis of the group of 18 patients with l.f. treated at the Otosurgery Department, Medical University of Lodz. In all patients the radical modified surgery has been performed. Postoperative results are strictly correlated to the l.f location and size. As a conclusion authors present an algorithm of the l.f. surgical treatment based on their experience.

Cholesteatoma, Middle Ear↗
PubMedDate not supplied

The caloric stimulus. Temperature generation within the temporal bone.

Temperature measurements were performed on isolated cadaveric temporal bones subjected to caloric irrigation of the external meatus. This was undertaken in an attempt to clarify the pathways of heat transfer involved in thermal stimulation of the temporal bone. On average, the maximum temperature change produced across the lateral semicircular canal was 0.47 degrees C, occurring 74 s after the start of the 30-s irrigation. Temperature changes of approximately 1.5 degrees C were found to occur in the air of the middle ear cleft, indicating significant heat transfer by the process of natural convection. By comparison, removal of the bony ridge joining the external meatus with the inner ear had little effect on the temperature generated across the lateral semicircular canal. It is therefore considered that natural convection within the middle ear cleft plays an important role in caloric stimulation of the vestibular labyrinth. This view is supported by the observation that there is a lack of a direct solid connection between the outer ear and lateral limb of the lateral semicircular canal.

Body Temperature Regulation↗
PubMed1992

Computer-aided three-dimensional measurement of the human vestibular apparatus.

Using a computer-aided three-dimensional reconstruction and measurement method, 12 measurements were made to determine the dimensions of the maculae, cristae ampullares, and semicircular canals in 18 temporal bones from nine pairs of age-matched male and female individuals (1 day to 76 years old). The surface areas of the utricular and saccular maculae were significantly larger in male than in female specimens (two-way analysis of variance, F = 9.00, df = 1, p less than 0.01; F = 4.57, df = 1, p less than 0.05, respectively). The width of the utricular macula and the length of the saccular macula were also significantly greater in male than in female specimens (two-way analysis of variance, F = 5.17, df = 1, p less than 0.05; F = 4.33, df = 1, p less than 0.05, respectively). Finally, the three semicircular canals were larger in diameter in male vs. female specimens; this difference was statistically significant for the superior semicircular canal (two-way analysis of variance, F = 10.74, df = 1, p less than 0.01). By contrast, none of these dimensions of those vestibular structures showed any significant change in size with advancing postnatal age. We propose from these findings that there appears to be sexual dimorphism in the vestibular apparatus.

Adolescent↗
PubMed1996

The subjective horizontal in eccentric rotation influenced by peripheral vestibular lesion.

Peripheral vestibular equilibrium disorders may originate in various parts of the labyrinth or the vestibular nerve. Traditionally, the function of the lateral semicircular canals has been assessed with caloric irrigation, and sometimes falsely been interpreted as a vestibular nerve lesion. The vertical semicircular canals are not easily assessed. Caloric testing with the head in different positions is not very helpful, but the canals may pairwise be tested using specific rotational techniques. Often the otolithic organs, capable of detecting linear acceleration forces, are forgotten as a source of vertigo and dizziness. We have implemented horizontal rotatory testing with the subject seated eccentrically facing the direction of rotation as a means of assessing otolithic function. The subject experiences a lateral tilt and is instructed in darkness to put a short light bar in the position he thinks a water surface would have, which is identical to his perceived tilt. In 39 normal subjects, a theoretical tilt of 24 degrees was estimated as approximately 19.5 degrees, and the standard deviation was 6 degrees. A side difference index was proposed to be normal if below 25%. The preliminary findings in a few patients with known labyrinthine lesions are presented. We propose that otolithic as well as lateral semicircular canal functions are useful to monitor in patients with suspected peripheral equilibrium disorders.

Adult↗
PubMed2000

Canal-otolith interactions after off-vertical axis rotations I. Spatial reorientation of horizontal vestibuloocular reflex.

We examined the three-dimensional (3-D) spatial orientation of postrotatory eye velocity after horizontal off-vertical axis rotations by varying the final body orientation with respect to gravity. Three rhesus monkeys were oriented in one of two positions before the onset of rotation: pitched 24 degrees nose-up or 90 degrees nose-up (supine) relative to the earth-horizontal plane and rotated at +/-60 degrees /s around the body-longitudinal axis. After 10 turns, the animals were stopped in 1 of 12 final positions separated by 30 degrees. An empirical analysis of the postrotatory responses showed that the resultant response plane remained space-invariant, i.e., accurately represented the actual head tilt plane at rotation stop. The alignment of the response vector with the spatial vertical was less complete. A complementary analysis, based on a 3-D model that implemented the spatial transformation and dynamic interaction of otolith and lateral semicircular canal signals, confirmed the empirical description of the spatial response. In addition, it allowed an estimation of the low-pass filter time constants in central otolith and semicircular canal pathways as well as the weighting ratio between direct and inertially transformed canal signals in the output. Our results support the hypothesis that the central vestibular system represents head velocity in gravity-centered coordinates by sensory integration of otolith and semicircular canal signals.

Algorithms↗
PubMed1988

Conduction of thermal stimuli in the human temporal bone.

Temperature changes at different locations in the labyrinth were measured in human temporal bone preparations after syringing with water. In order to simulate physiological conditions, the preparations were placed in a water bath at 37 degrees C. The maximum temperature changes in the horizontal semicircular canal after syringing with temperatures symmetrical to body temperature (44 degrees or 30 degrees C) were found to be clearly asymmetrical (with mean values of 0.6 and -0.3K). From measurements in the external auditory meatus, findings showed that the reference temperature was 34 degrees C in front of the tympanic membrane, which explains the asymmetry recorded. Measurements at different locations showed that the temperature first changes in the regions of the ampullae of the horizontal and the superior semicircular canals. In the vestibule the onset and decay of the temperature change is delayed. The time courses of the temperature difference between locations demonstrate that the temperature difference across the horizontal semicircular canal, which would be responsible for any convective effect in the endolymph, is of shorter duration than the absolute temperature change, which would be responsible for any temperature-mediated volume changes.

Adult↗
PubMed1999

Cogan's syndrome: clinical significance of antibodies against the inner ear and cornea.

The aim of this study was to evaluate the pathological significance of antibodies against cornea and inner ear tissue in the development of audiovestibular and ocular symptoms in patients with Cogan's syndrome (CS). We analysed the serum of 5 CS patients for binding of IgM and IgG to fresh cryosections of rat labyrinth (semicircular canals, ampulla, utricle, saccule) and cornea by indirect immunofluorescence (IF). The predominant pattern of anti-corneal IgM was staining of the superficial cell layer of the non-keratinizing squamous epithelium. IgM against cornea was found in 3 patients, all of whom had bilateral inflammatory eye signs at the start of the disease. However, IgM was also detected in the chronic stage of the disease when no clinical signs of eye involvement were apparent. The study includes the first follow-up examination of anti-corneal IgM and IgG antibodies during a complete episode of active CS. During the first episode of CS in 1 patient, anti-corneal IgM became detectable 1 week after the onset of interstitial keratitis and 3 weeks after the onset of audiovestibular symptoms. It increased over several weeks and then fell to very low levels. However, at no time was anti-corneal IgG found. In the course of follow-up examinations, the serum of 4 patients intermittently contained low titre IgG antibodies against inner ear labyrinthine tissue, but without any clear correlation with the active stages of CS. In addition, high-resolution MRI (HR-MRI) of the inner ear was performed in the acute and chronic stages of CS to evaluate the activity of CS. In the acute stage, HR-MRI revealed abnormal MRI signals in the vestibule, semicircular canals, vestibular nerve, or cochlea. In the chronic stage, patients showed narrowing or occlusion of semicircular canals and the cochlea on the 3D-CISS images, but no high signal lesions (T1) and no enhancement. Antibodies against cornea or labyrinthine tissue were not consistently detected in CS and the level of organ-specific antibodies did not correlate with the activity of the disease.

Acute Disease↗
PubMed2001

Benign paroxysmal positional vertigo.

Benign paroxysmal positional vertigo (BPPV) is the most common and most treatable cause of vertigo. In most cases, a simple maneuver that takes less than a few minutes to do resolves the problem. BPPV is caused by misplaced calcium carbonate crystals (otoconia) in the semicircular canal of the inner ear that have broken free from the utricle. When these crystals break free, they either remain loose in one of three different semicircular canals or attach to the hair cells within a canal. Several different types of treatment maneuvers have been described. The maneuver to use varies according to the semicircular canal involved and whether the crystals are loose or attached to the hair cells.

Humans↗
PubMed1993

Responses of caudal medullary raphe neurons to natural vestibular stimulation.

1. Over two thirds of caudal medullary raphespinal neurons respond to electrical stimulation of the vestibular nerve, and it has been suggested that these neurons may participate in the generation of vestibulospinal and vestibulosympathetic reflexes. The objective of the present study was to determine which vestibular endorgans (semicircular canals or otolith organs) provide inputs to these cells. 2. Experiments were conducted on decerebrate cats that were baroreceptor denervated and vagotomized, and that had a cervical spinal cord transection so that inputs from tilt-sensitive receptors outside of the labyrinth did not influence the units we recorded. 3. In most experiments, vertical vestibular stimulation was used to stimulate the anterior and posterior semicircular canals and the otolith organs. The plane of whole body rotation that produced maximal modulation of a neuron's firing rate (response vector orientation) was measured at one or more frequencies between 0.1 and 0.5 Hz. Neuron dynamics were then studied with sinusoidal (0.02-1 Hz) stimuli aligned with this orientation. Alternatively, in two animals horizontal rotations at 0.5 and 1.0 Hz were employed to stimulate the horizontal semicircular canals. 4. The properties of raphespinal neurons were similar to those of a larger sample of raphe neurons studied that either could not be antidromically activated from the cervical spinal cord or were not tested for a spinal projection. In response to vertical vestibular stimulation, > 85% of caudal medullary raphe neurons had response gains that remained relatively constant across stimulus frequencies, like regularly firing otolith afferents.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗
PubMed1990

Temporal bone histopathologic findings in Alagille's syndrome.

Six temporal bones obtained from four individuals with Alagille's syndrome, aged 4 months and 3, 6, and 7 years, were studied histopathologically. The external auditory canals and tympanic membranes were normal. Although the stapes, the interossicular joints, and the subarcuate fossae were slightly underdeveloped in the majority of cases, the other structures in the middle ear were almost normal. However, severe anomalies were observed in structures in the inner ear. In all cases, both the bony and membranous structures of the posterior semicircular canal were partially or totally absent, and, in three ears, those of the anterior semicircular canal were also partially absent; the lateral semicircular canal, however, was normal in all cases. The cochlea was observed to be shortened in only one case.

Abnormalities, Multiple↗