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PubMed1999

Partial labyrinthectomy with hearing preservation: frequency-specific data using tone-burst auditory brain stem response.

Surgical approaches to the inner ear with hearing preservation have valuable implications for neurotologic surgery. In a previous study in guinea pigs, we demonstrated that click-evoked auditory brain stem responses (ABRs) were preserved after transection and plugging of 1 or more semicircular canals but were lost after entering the vestibule (Smouha EE, et al. Otolaryngol Head Neck Surg 1996; 114:777-784). A limitation of that study was that click-evoked ABR might not represent the function of the entire cochlea. In this study we used tone-burst ABR to determine thresholds across a broad range of frequencies (2 to 24 kHz) before and after surgical entry into the labyrinth at the lateral semicircular canal, ampulla, and vestibule. Serial measurements were made, and a sham surgery group was used as a control. The results obtained with tone-burst ABR generally agreed with those previously obtained with click stimuli. Toneburst ABR thresholds were similar across most frequencies tested. Transection of the lateral semicircular canal resulted in preservation of ABR thresholds. Ampullectomy had a variable effect on ABR thresholds. Vestibulotomy usually resulted in substantial hearing loss. We conclude that hearing can be preserved across a range of frequencies after selective surgery of the inner ear. Surgical entry into the membranous labyrinth near the vestibule is the critical factor contributing to hearing loss after partial labyrinthectomy.

Animals↗
PubMed2005

The effect of superior canal dehiscence on cochlear potential in response to air-conducted stimuli in chinchilla.

A superior semicircular canal dehiscence (SCD) is a break or hole in the bony wall of the superior semicircular canal. Patients with SCD syndrome present with a variety of symptoms: some with vestibular symptoms, others with auditory symptoms (including low-frequency conductive hearing loss) and yet others with both. We are interested in whether or not mechanically altering the superior canal by introducing a dehiscence is sufficient to cause the low-frequency conductive hearing loss associated with SCD syndrome. We evaluated the effect of a surgically introduced dehiscence on auditory responses to air-conducted (AC) stimuli in 11 chinchilla ears. Cochlear potential (CP) was recorded at the round-window before and after a dehiscence was introduced. In each ear, a decrease in CP in response to low frequency (<2 kHz) sound stimuli was observed after the introduction of the dehiscence. The dehiscence was then patched with cyanoacrylate glue leading to a reversal of the dehiscence-induced changes in CP. The reversible decrease in auditory sensitivity observed in chinchilla is consistent with the elevated AC thresholds observed in patients with SCD. According to the 'third-window' hypothesis the SCD shunts sound-induced stapes velocity away from the cochlea, resulting in decreased auditory sensitivity to AC sounds. The data collected in this study are consistent with predictions of this hypothesis.

Acoustic Stimulation↗
PubMed1995

Inertial representation of angular motion in the vestibular system of rhesus monkeys. II. Otolith-controlled transformation that depends on an intact cerebellar nodulus.

1. We recently studied the spatial representation of angular motion signals in rhesus monkeys by examining the orientation of postrotatory vestibuloocular responses during tilt of the head and body relative to gravity after constant-velocity rotation about an earth-vertical axis. We have reported that low-frequency angular motion signals in the vestibuloocular reflex (VOR) of rhesus monkeys are spatially transformed such that they remain invariant relative to gravity. In the present study we examine the properties of these inertial vestibular signals by employing similar stimulation conditions in animals with either selective semicircular canal plugging or selective lesions of cerebellar lobule X (nodulus) and ventral lobule IX (uvula). 2. We studied the spatial organization of postrotatory VOR in two rhesus monkeys that had either the lateral or one of the vertical canal pairs inactivated by plugging. In both monkeys, the spatiotemporal characteristics of postrotatory velocity after rotation in the plane of an intact canal pair and tilting in the plane of the plugged canal pair were indistinguishable from those of intact animals: postrotatory responses after tilts in the plane of the plugged canal pair were strongly damped, whereas an orthogonal response component was generated that rotated the eye velocity vector toward alignment with gravity. Thus otolith information rather than transient semicircular canal inputs that normally coexist during tilts seem to provide the necessary cues for the central transformation of semicircular canal signals. 3. We studied the three-dimensional VOR properties in two animals in which the cerebellar nodulus and ventral uvula were surgically ablated. After these lesions the temporal properties of the horizontal, vertical, and torsional VOR during earth-vertical-axis rotations were differentially affected. For horizontal VOR, the duration of postrotatory nystagmus was prolonged and the responses acquired strongly underdamped (i.e., oscillatory) properties. Similarly, sinusoidal responses were characterized by smaller phase leads after the lesion. For torsional VOR, the duration of postrotatory nystagmus was significantly shorter after the lesions, reaching postlesion values of 3.6 +/- 1.7 (SD) s and 6.4 +/- 1.1 s compared with prelesion values of 22.4 +/- 4.5 and 33.6 +/- 5.3 s for each animal. In addition, large phase leads characterized the torsional VOR during low-frequency sinusoidal stimulation. The dynamic properties of the vertical VOR in the lesioned animals, on the other hand, were indistinguishable from those in controls. 4. The cerebellar lesions affected the spatial organization of the horizontal and vertical/torsional systems in a differential way. Inertial transformation of lateral canal activity was only partially affected.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1998

Subjective Visual Horizontal Determination During Otolith Stimulation by Eccentric Rotation in Conservatively Treated Meniere's Disease.

Peripheral vestibular equilibrium disorders may originate in various parts of the labyrinth or of the vestibular nerve. Traditionally, the function of the lateral semicircular canals has been assessed by caloric irrigation and has been interpreted (sometimes falsely) as demonstrating a vestibular nerve lesion. The vertical semicircular canals are not assessed easily. Caloric testing with the head in various positions is not very helpful, but the canals may be tested in pairs using specific rotational techniques. Often, the otolith organs, detecting linear acceleration forces, are forgotten as a source of vertigo and dizziness. The extent of otolith involvement in Meniere's disease is not well understood. The tested subject is seated eccentrically in a rotatory chair and faces the direction of rotation. Thus, the otolith organs are stimulated in steady-state rotation. The subject experiences a lateral tilt and, in darkness, is instructed to point a short light bar in the position that he or she thinks a water surface would have (identical to the perceived tilt). Patients with conservatively treated unilateral Meniere's disease were tested. In the eccentric rotation test, the patients with unilateral Meniere's disease showed highly variable, sometimes even paradoxical, responses. No correlation was noted between the eccentric otolith test and pure-tone audiometry or the side difference of the caloric responses. Otolith and lateral semicircular canal functions may differ in patients with Meniere's disease, the nature of which remains to be elucidated in further studies.

Journal Article↗
PubMed2002

Altered cupular mechanics: a cause of peripheral vestibular disorders?

It has taken many decades to arrive at today's concept of cupula mechanics in the stimulation of endolymphatic flows on the hair cells in the ampullae of the semicircular canal. While Steinhausen assumed free swing-door movement of the cupula in the 1930s, Hillman was the first to demonstrate firm cupula attachment to the ampulla wall as a physiological necessity in the 1970s. In contrast to the present clinical concepts of acute peripheral vestibular functional disorders (circulatory disturbances, viral or bacterial infection, altered electrolytes in the endolymph), this study examines the extent to which an impaired attachment mechanism can trigger peripheral vestibular disorders. For this purpose, we used a pigeon model (n = 8), in which mechanical detachment of the cupula from the ampulla wall was achieved by means of a targeted pressure increase in the ampulla of the lateral semicircular canal. In two additional animals the labyrinth was completely destroyed on one side in order to directly compare partial and complete vestibular disorders. In this way partial damage to the lateral semicircular canal ampulla presents a clinical picture whose symptoms are very similar to those of an idiopathic vestibular disorder in humans. Their intensity and course of compensation differ markedly from the symptoms of complete vestibular destruction. Subsequent histological examination revealed that the hair cells remained intact during the experimental detachment of the cupula. Our results thus show that only altered cupula mechanics seem to trigger the clinical picture of a peripheral vestibular disorder. This may result in completely new approaches to differential diagnosis and the therapy of vestibular neuronitis.

Animals↗
PubMedDate not supplied

Long-term postural abnormalities in benign paroxysmal positional vertigo.

Benign paroxysmal positional vertigo (BPPV) is a disorder in which patients suffer from acute rotatory vertigo due to the presence of free otoconial debris migrating into one or more semicircular canals during head movements and resulting in abnormal stimulation of the ampullary crest. A prolonged loss of equilibrium of unclear origin is also present. Static posturography is a useful tool for the study of postural control systems and their role in these abnormalities. The aim of the present study was to evaluate the frequency of body sway and long-term instability of BPPV patients by posturography frequency analysis. Twenty patients with canalithiasis of the posterior semicircular canal and 20 normal controls were subjected to static posturography. Informed consent was obtained from all subjects. Patients were tested 1 h after diagnosis, and 3 days and 12 weeks after the characteristic Epley repositioning maneuver. Patients with BPPV showed significantly increased body sway both on lateral (X) and anteroposterior (Y) planes compared to normal subjects. Corporal oscillation with a broad-frequency spectrum was observed in both closed and open eye tests. The repositioning maneuver decreased the X plane body sway, while the anteroposterior sway was unchanged. Twelve weeks after treatment, a normalization of the anteroposterior sway was observed. Results of this study suggest that the long-term postural disturbance associated with BPPV differs from the acute disequilibrium that subsides after canalith repositioning: the former is a sagittal plane/broad spectrum body sway, while the latter is primarily a frontal plane/low frequency sway. The Epley maneuver was shown to reduce frontal sway, a postural abnormality that might therefore be linked to posterior semicircular canal function. Conversely, the observed sagittal body sway was only partially relieved by the restoration of canal function, and therefore, may be more related to the chronic dizziness observed in these patients.

Adult↗
PubMedDate not supplied

Benign paroxysmal positional vertigo of the horizontal canal: a form of canalolithiasis with variable clinical features.

Benign paroxysmal positional vertigo of the horizontal semicircular canal (HC-BPPV) is a well-defined syndrome characterized by direction-changing horizontal positional nystagmus. We report the clinical features of 5 patients who illustrate the possible variables of the syndrome. In most cases, nystagmus is geotropic and more intense when the pathological ear is lowermost; less often the syndrome presents with apogeotropic nystagmus that is more intense when the affected ear is uppermost. The nystagmus pattern may vary in time in the same patient, changing from apogeotropic to geotropic even in observations at short intervals. In some patients, the features indicate involvement of more than one canal, either simultaneously or in succession. It is sustained that the clinical findings can be explained by movement of endolymph caused by displacement of otoconia in the semicircular canals and that variants are due to different positions of the otoconia within the canals.

Adult↗
PubMed1996

[Developmental studies on the petrous part of the human temporal bone--special references to the morphogenesis of the facial nerve canal].

Development and formation of the petrous bone was examined in total of 343 Japanese skulls. The materials used consisted of 310 skulls of Japanese fetuses ranging from the fourth to tenth month, 19 skulls of Japanese juveniles from the third month to 7 years of age, and 20 temporal bones obtained from 14 adult cadavers. A total of six group of ossification centers appear in the petrous part during 5th fetal month, and they form the petrous bone at 6th fetal month. The firstly-appeared ossification center is just above the round window, and the second is on the ampulla of anterior semicircular canal. Other ossifications are observed between the cochlea and semicircular canals, on the brim of internal acoustic porus, on the superior surface of the petrous apex, and on the summit of posterior semicircular canal. The ossification of the facial canal starts at 6th fetal month, though the geniculate part and tympanic part do not complete until one year old after birth. Even in adults, the facial canal dehiscence are found at more than 10% of cases, mainly locating in the tympanic part. On the basis of these results, formation of the petrous bone including facial canal and other bony structures was discussed from the viewpoints of the ossification and pre- and postnatal middle ear development.

Adult↗
PubMed1984

A quantitative analysis of the spatial organization of the vestibulo-ocular reflexes in lateral- and frontal-eyed animals--II. Neuronal networks underlying vestibulo-oculomotor coordination.

The neuronal connectivity underlying the vestibulo-ocular reflexes in cat and rabbit was evaluated in the light of quantitative data of the spatial orientation on semicircular canals and extraocular muscles. Neuronal connectivity was calculated using a matrix-analysis of the sensory and motor periphery, and of the brain stem pathways connecting semicircular canals and extraocular muscles. Two cases of vestibulo-ocular reflex compensation were considered. In the first case, vestibulo-oculor reflex compensation was assumed to be isotropic, i.e. the vestibulo-ocular reflex gain is the same for all directions of rotation. In the second case, the vestibulo-oculor reflex gain was assumed to be anisotropic with the "torsional" gain smaller than the "horizontal" and "vertical" gains. The theoretical calculation predicts that besides the principal vestibulo-ocular reflex pathways (classical three-neuron-arc connectivity), several accessory connections (other than principal connections, regardless of the synapses involved) exist which are characteristic for each species. These accessory connections were compared to physiological and anatomical data. In the cat theoretical connections for an isotropic vestibulo-ocular reflex gain agree with pathways observed experimentally, of which the most characteristic are excitatory connections to the superior rectus and inhibitory connections to the inferior rectus muscle from both of the anterior canals, and a mirror image pattern of connections from the posterior canals. In the rabbit experimentally obtained data and calculated connections rarely agree. However, for an anisotropic gain we find a higher rate of coincidence between experimental and theoretical connections. Our evaluation indicates, that accessory vestibulo-ocular reflex pathways serve to compensate for the incongruence between semicircular canal and extraocular muscle planes, at least in the cat. Available experimental data suggest an important role of a special subclass of accessory pathways via axon collaterals of principal projections (three-neuron-arc nature). With certain restrictions, the presented method of calculation promises to be a useful tool for a quantitative analysis of the vestibulo-ocular reflex.

Animals↗
PubMed2005

Postural stability in patients with different durations of benign paroxysmal positional vertigo.

Postural stability maintenance was investigated in patients with "idiopathic" benign paroxysmal positional vertigo of the posterior semicircular canal (BPPV-PSC) and compared to healthy subjects. To measure the postural stability during a quiet upright stance, we used static posturography in two conditions: with open and with closed eyes. The effect of the repositioning Epley's maneuver on the recovery of postural stability in patients with different durations of BPPV-PSC less than 60 days after the first attack of positioning vertigo (group I) and more than 60 days (group II) was examined. The investigation was made 1 h after the positive Dix-Hallpike test and 7 days after treatment with the Epley maneuver. "Sway velocity" (SV) and "relative power spectrum" (RPS) of the stabilograms were calculated to evaluate the postural stability for each subject and each experimental condition. We found a pronounced spectral density peak in the frequency range of 1.0-2.0 Hz and smaller spectral density in the range of 0.15-0.5 Hz compared to that in healthy subjects. Our results showed that the postural maintenance in BPPV-PSC patients depended on the disease duration. Patients with a duration of BPPV symptoms less than 60 days after the first attack demonstrated a high dependence on the visual input for postural stability. One week after the Epley maneuver, differences in the recovery of postural control in both groups of patients were also found. We assume that the disturbed otolith function together with the impaired dynamics of the semicircular canal generate a particular pattern of postural maintenance. The different degree of restoration of postural stability 1 week after the EM treatment in BPPV-PSC patients with different durations of the disease gives us reason to believe that after removing the otoconia from the semicircular canal, some stimulation of other sensory subsystems and adaptation mechanisms occur that lead to a new pattern of postural maintenance.

Follow-Up Studies↗
PubMed1991

Influence of vestibular and visual climbing fiber signals on Purkinje cell discharge in the cerebellar nodulus of the rabbit.

Extracellular recordings of the climbing fiber responses (CFRs) of single Purkinje cells were made in the cerebellar nodulus and ventral uvula of anesthetized pigmented rabbits. Natural vestibular and optokinetic stimuli were used to evoke responses from these Purkinje cells. Using a null response technique we sorted vestibularly-evoked CFRs into two canal-related categories. CFRs were related to either the ipsilateral anterior and contralateral posterior semicircular canal (iAC+cPC) or to the ipsilateral posterior and contralateral anterior semicircular canal (iPC+cAC). Both canal-related CFRs also responded to downward optokinetic stimulation.

Acceleration↗
PubMed1996

Mutations affecting development of the zebrafish ear.

In a large scale screen for genetic defects in zebrafish embryogenesis we identified mutations affecting several aspects of ear development, including: specification of the otic placode, growth of the otic vesicle (otocyst), otolith formation, morphogenesis of the semicircular canals and differentiation of the otic capsule. Here we report initial phenotypic and genetic characterization of 20 of these mutations defining 13 independent loci. Embryos mutant at the quadro locus display abnormal specification of the otic placode. As revealed by dlx-3 expression, the otic field in the mutant embryos is smaller or split into two fields. At later stages of development the ear of quadro mutants is frequently divided into two smaller, incomplete units. Four loci affect ear shape shortly after formation of the otic vesicle. All of them also display abnormal brain morphology. Mutations in five loci result in the absence of otolith formation; two of these also produce changes of ear morphology. Two loci, little richard and golas, affect morphology of the otic vesicle shortly before formation of the semicircular canals. In both cases the morphogenesis of the semicircular canals is disrupted. Finally, the antytalent locus is involved in late expansion of the ear structure. Analysis of mutations presented here will strengthen our understanding of vertebrate ear morphogenesis and provide novel entry points to its genetic analysis.

Animals↗
PubMed2004

The effect of postural restrictions in the treatment of benign paroxysmal positional vertigo.

The treatment of benign paroxysmal positional vertigo (BPPV) consists of a repositioning maneuver in order to remove otoliths from the posterior semicircular canal and subsequent postural restrictions to prevent debris from reentering the canal. However, the extent to which postural restrictions affect the final outcomes of BPPV is still uncertain. The purpose of this study is to determine the effects of postural restrictions in the treatment of BPPV, which is caused by otoliths in the posterior semicircular canal, and to evaluate its usefulness as a therapy. Seventy cases diagnosed as BPPV of the posterior semicircular canal were studied. All patients were treated utilizing the modified Epley maneuver. They were divided into two groups. The first group (group A, 35 patients) was instructed to sleep in a semi-sitting position and to avoid moving their heads forward or backward, whereas no instructions were given to the second group (group B, 35 patients). The information gathered from the patients was analyzed by age of onset, gender, duration of the disease and cure rates or recurrence rates. In group A, the average age was 54.5 years and the mean duration of symptoms was 116.5 days, whereas in group B, these measurements were 54.8 years and 86.7 days. The cure rates were 91.4 and 94.3%, respectively. Symptoms recurred in 12.5% of group A patients, while in group B, there was a 9.1% recurrence rate. Our study did not show any significant difference between the two groups. Postural restriction therapy, practiced after the modified Epley repositioning maneuver, did not have a significant effect on the final outcomes of BPPV. Based on our results, we do not recommend this therapy since there was no significant benefit for the patients who utilized postural restrictions.

Adult↗
PubMed2001

Temporal bone anomaly proposed as a major criteria for diagnosis of CHARGE syndrome.

The acronym CHARGE defines a non-random clustering of congenital malformations of unknown origin. Classical diagnostic criteria include: 1) one major feature namely coloboma/microphthalmia or choanal atresia, and 2) four of the six features designated in the CHARGE acronym. Interestingly, all CHARGE patients hitherto reported had partial or complete semicircular canal hypoplasia on temporal bone CT-scan. We report on semicircular canal agenesis/hypoplasia in three patients with three to four features of the CHARGE syndrome and neither coloboma nor choanal atresia and we propose to include temporal bone malformations as a major criteria for diagnosis of CHARGE syndrome.

Abnormalities, Multiple↗
PubMed1994

Computerized tomographic findings in endolymphatic sac surgery in Menière's disease.

We correlated the surgical findings and the findings of computerized tomographic scans of the temporal bone in 38 ears from 38 patients with Menière's disease (31 unilateral and 7 bilateral) treated by endolymphatic sac (ES) drainage surgery between 1986 and 1991. At surgery, the position and size of the ES were recorded. The position of the ES was classified as one of three types according to Arenberg's parameters (type I, type II and type III) and the size of the ES was classified as large, intermediate or small. Scans encompassing the lateral semicircular canal were used to measure the minimum distance between the posterior semicircular canal and the posterior petrous surface (P-P distance). The P-P distance in 23 type III cases was significantly shorter (2.25 mm) than in 13 type II cases (3.39 mm). The P-P distance in 9 large-sized ES cases was significantly longer (3.99 mm) than in 20 intermediate-sized ES cases (2.40 mm) and in 9 small-sized ES cases (1.92 mm). Significant correlations were found in patients with Menière's disease between a short P-P distance and type III ES position, and also between a short P-P distance and an intermediate or small-sized ES.

Cephalometry↗
PubMed1992

Cristospinal reflex in circular walking.

This study comprised 22 normal adults, 12 males and 10 females. Electromyograms of the bilateral gastrocnemius muscle were recorded during circular walking under two conditions: no caloric stimulation and immediately after irrigating the right auditory canal with 20 degrees C water for 20 s with the horizontal semicircular canal maintained in vertical position. With no caloric stimulation, gastrocnemius muscle activity on the right side exceeded that on the left during dextrorotation and vice versa during sinistrorotation. Following irrigation of the right auditory canal, the activity was greater on the left side than on the right during sinistrorotation, but no consistent differences in muscle activity were observed during dextrorotation. Dextrorotation was associated with ataxic gait in all cases. Thus ampullopetal lymphatic flow in the semicircular canal due to circular walking causes increased antigravity muscle tonus of the ipsilateral leg. This gives the ipsilateral leg assistance for supporting body weight which shifts to the inner side of circular walking.

Adult↗
PubMed2004

Torsional vestibulo-ocular reflex during whole-body oscillation in the upright and the supine position: II. Responses in patients after vestibular neuritis.

In a recent study we demonstrated that otolith input modifies the torsional angular vestibulo-ocular reflex (torVOR) of healthy human subjects: Compared to turntable oscillations in supine position, oscillations in upright position increased the gain of torVOR by 0.1 and cancelled the phase lead originating from low-frequency semicircular canal signals. We asked whether these otolith-related changes of torVOR are still present in patients after vestibular neuritis (VN). Eight patients were sinusoidally oscillated about their naso-occipital axis in supine (canal-only stimulation) and upright (canal-and-otolith stimulation) position. Three-dimensional eye movements were recorded with dual search coils. The patients showed similar otolith-related gain and phase changes of the torVOR as healthy subjects: the gain increased by about 0.1 (p < 0.05) and the low-frequency phase lead from semicircular canal signals was abolished. These results indicate that otolith function after VN is still sufficient to interact with semicircular canal signals to optimize torsional gaze stabilization when the head is upright.

Adult↗