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PubMed1994

Mechanics of caloric stimulation in a case with a plug in the horizontal semicircular canal.

Horizontal eye movements were recorded by electronystagmography in a subject with a plug of granulation tissue in the unilateral horizontal semicircular canal by the room temperature air caloric stimulation. Stimuli were sequentially presented to both ears with the subject supine and prone, keeping the horizontal canal vertical. Caloric stimuli presented to the unplugged ear resulted in a vestibular nystagmus whose slow phase eye velocity (SPEV) was always directed toward the stimulated side when the subject was supine and toward the opposite side when he was prone. In contrast, calorics presented to the horizontal canal plugged ear showed that SPEV was always directed toward the stimulated side, irrespective of whether the subject was supine or prone. Results were consistent with consensus that the caloric responses noted in the horizontal canal plugged ear reflected horizontal canal afferent activity which may correspond to direct effect of temperature on end organs or afferents. The findings imply that a caloric mechanism exists which is independent of the conventionally accepted one involving concection currents within the canal.

Aged↗
PubMed2000

Unilateral semicircular canal aplasia in Goldenhar's syndrome.

A patient with Goldenhar's syndrome (oculoauriculovertebral dysplasia) and unilateral aplasia of all semicircular canals is presented. This is the first report of such a finding and may support the hypothesis that Goldenhar's syndrome and the CHARGE association have a common pathogenetic mechanism.

Fourier Analysis↗
PubMed1996

Mechanical versus CO2 laser occlusion of the posterior semicircular canal in humans.

The purpose of this study was to compare the effectiveness of mechanical and laser-assisted posterior semicircular canal occlusion (PCO) for the treatment of intractable benign paroxysmal positional vertigo (BPPV). Twelve consecutive patients with intractable BPPV underwent PCO by three surgeons, six with mechanical PCO and six with CO2 laser-assisted PCO. PCO eliminated positional vertigo in all patients treated with the laser and five of six patients treated without the laser. Dysequilibrium was present in all patients immediately postoperatively. This resolved in all patients treated with the CO2 laser but in only two of six patients treated without the laser (p = 0.03). Patients were hospitalized for dysequilibrium for an average of 5.2 and 2.8 days for the mechanical and laser-assisted groups, respectively. Preoperative and postoperative hearing was not significantly different between the groups. No clinically significant postoperative hearing loss was encountered in either group. These results suggest that PCO is an effective treatment for intractable BPPV. The incidence of dysequilibrium that persists following PCO may be reduced by using the CO2 laser to seal the membranous canal prior to occluding the bony canal.

Adult↗
PubMed1978

Semicircular canal stimulation in cerebral palsied children.

Twelve cerebral palsied children were exposed to 16 sessions of horizontal and vertical semicircular canal stimulation over a four-week period in order to determine the effectiveness of this form of stimulation as a therapeutic procedure. A control group of 11 cerebral palsied children was included. A quantitative evaluation of a series of reflexes and of gross motor skills showed a highly significant degree of improvement following the four weeks of treatment. A qualitative evaluation of each subject corroborated these findings and suggested improvements in fine motor control and in social/emotional behavior. A possible central nervous system mechanism underlying the improvement in motor skills is discussed.

Cerebral Palsy↗
PubMed1989

[Mechanisms of development of the dome in the semicircular canals of birds. II. Cellular reorganization].

A light microscopic study of the epithelia of the crista ampullaris of the semicircular canals of the embryonic chicken indicates that the epithelial cells undergo irregular degenerative changes, with continual mitotic replacement of surface cells. The cupula develops over the surface epithelia through vesicular secretions containing acidophils fibrillar material mixed with globular formations derived from fragmentation of the surface epithelial cells. Electron microscopic studies demonstrate the mode of secretion of rounded or oval supraepithelial bodies from surface epithelium, contributing to the development of the cupula ampullaris. These observations provide evidence of cytoplasmic contributions of surface epithelial cells of the crista ampullaris contributing to the development and continued reorganization of the cupula ampullaris during embryonic development.

Animals↗
PubMed1990

Efferent vestibular system in the toadfish: action upon horizontal semicircular canal afferents.

The influence of the efferent vestibular system (EVS) upon the background discharge and response dynamics of horizontal semicircular canal afferents was examined in the toadfish. In one set of experiments the EVS was activated using a behavioral paradigm; in the second, electrical shocks were applied to the efferent vestibular nucleus in the brain stem. The afferent's background discharge and responses to rotation were recorded before and during efferent stimulation. Both EVS activation paradigms gave qualitatively similar results: a facilitation of the afferent's rate, while the animal was at rest or in motion, and a reduction in response sensitivity. Afferents were not affected uniformly: low-gain, velocity-sensitive afferents were weakly influenced, while high-gain and acceleration afferents having low rates were the most excited. The afferents' phase of response was unmodified by electrical EVS stimulation. In many afferents a prominent form of response nonlinearity is discharge silencing over large portions of the stimulus cycle. Efferent-evoked rate increase was often sufficient to produce a full-cycle bidirectional response. Caloric facilitation of afferent rate confirmed that the EVS-induced sensitivity decrease was rate independent. These results show a dual action of the efferent system: (1) facilitating the afferent's rate and (2) reducing its sensitivity to adequate stimulation that may be correlated with the dual EVS synaptic innervation of the labyrinth, namely postsynaptic efferent-afferent synapses and presynaptic efferent-hair cell synapses.

Animals↗
PubMed2004

Superior semicircular canal dehiscence presenting as conductive hearing loss without vertigo.

OBJECTIVE: The objective of this study was to describe superior semicircular canal dehiscence (SSCD) presenting as otherwise unexplained conductive hearing loss without vestibular symptoms. STUDY DESIGN: Retrospective. SETTING: Tertiary referral center. PATIENTS: The study comprised 8 patients (10 ears), 5 males and 5 females aged 27 to 59 years. All 10 ears had SSCD on high-resolution computed tomography scan of the temporal bone. DIAGNOSTIC TESTS AND RESULTS: All 10 ears had significant conductive hearing loss. The air-bone gaps were largest in the lower frequencies at 250, 500, and 1000 Hz; the mean gaps for these 3 frequencies for the 10 ears were 49, 37, and 35 dB, respectively. Bone-conduction thresholds below 2000 Hz were negative (-5 dB to -15 dB) at one or more frequencies in 8 of the 10 ears. There were no middle ear abnormalities to explain the air-bone gaps in these 10 ears. Computed tomography scan and laboratory testing indicated lack of middle ear pathology; acoustic reflexes were present, vestibular evoked myogenic potentials (VEMPs) were present with abnormally low thresholds, and umbo velocity measured by laser Doppler vibrometry was above mean normal. Middle ear exploration was negative in six ears; of these six, stapedectomy had been performed in three ears and ossiculoplasty in two ears, but the air-bone gap was unchanged postoperatively. The data are consistent with the hypothesis that the SSCD introduced a third mobile window into the inner ear, which in turn produced the conductive hearing loss by 1) shunting air-conducted sound away from the cochlea, thus elevating air-conduction thresholds; and 2) increasing the difference in impedance between the oval and round windows, thus improving thresholds for bone-conducted sound. CONCLUSION: SSCD can present with a conductive hearing loss that mimics otosclerosis and could explain some cases of persistent conductive hearing loss after uneventful stapedectomy. Audiometric testing with attention to absolute bone-conduction thresholds, acoustic reflex testing, VEMP testing, laser vibrometry of the umbo, and computed tomograph scanning can help to identify patients with SSCD presenting with conductive hearing loss without vertigo.

Acoustic Impedance Tests↗
PubMed2001

Special issue: Symposium on "Morphology and Physiology of Semicircular Canal Ampulla".

This issue of Biological Sciences in Space includes papers presented at the symposium on "Morphology and Physiology of Semicircular Canal Ampulla" held in Nagoya, Japan, on March 25-27, 2001. The symposium was organized as part of the Japan-German Collaboration Project, a collaboration initiated in 1986 of the Japan Society for Promotion of Sciences and Deutsche Forschungs-gemeinschaft.

Animals↗
PubMed2004

Central distribution of vestibular afferents that innervate the anterior or lateral semicircular canal in the mongolian gerbil.

The central distribution of afferents that innervate the crista ampullaris of the anterior or lateral semicircular canals was determined in gerbils following the direct injection of tracers into one sensory neuroepithelia. Labeled somata were scattered throughout the superior ganglion. The central distribution of fibers demonstrated extensive overlap. The central branch of afferents innervating either canal was located in the rostral part of the nerve. Nerve fibers divided into ascending and descending branches. Ascending branch ramifications terminated in the superior vestibular nucleus, the magnocellular and parvicellular medial vestibular nuclei, and the cerebellum. Cerebellar terminal areas include the flocculus, nodulus and uvula. Descending branch ramifications terminated in the caudal medial, parvicellular medial and descending vestibular nuclei, and the nucleus prepositus hypoglossi. Lateral canal afferents terminated sparsely in nucleus cuneatus. The anterior canal had sparse innervation in the paratrigeminal and gigantocellular reticular formation. This study has shown many similarities in the central distribution of fibers that innervate the anterior and lateral canals and a few areas of segregated input. Projections outside the vestibular nuclei are more extensive than previously determined, including afferents to prepositus hypoglossi, cochlear nuclei, and reticular formation. Projections to the flocculus appear as numerous as those to the vermis.

Afferent Pathways↗
PubMed2003

Dehiscence of bone overlying the superior semicircular canal as a cause of an air-bone gap on audiometry: a case study.

Dehiscence of bone overlying the superior semicircular canal can result in a syndrome of vertigo and oscillopsia induced by loud noises or by maneuvers that change middle ear or intracranial pressure. Patients with this disorder can also experience a heightened sensitivity to bone-conducted sounds in the presence of normal middle ear function. High-resolution CT scans of the temporal bones demonstrate the dehiscence. The authors describe a patient with bilateral superior canal dehiscence who had bilateral low-frequency conductive hearing loss, normal middle ear function, intact acoustic reflexes, and intact vestibular-evoked myogenic potentials. These findings would not be expected on the basis of a middle ear cause of the conductive hearing loss. A high-resolution CT scan of the temporal bones in this patient revealed bilateral superior canal dehiscence. Normal acoustic immittance findings in the presence of conductive hearing loss should alert clinicians to the possibility of inner ear cause of an air-bone gap due to superior canal dehiscence.

Audiometry↗
PubMed2005

Contribution of endolymphatic fluid shift to caloric response in plugged semicircular canals.

The purpose of this study was to clarify the role of endolymphatic fluid shift in caloric response, using frog posterior semicircular canals (PSCs). PSCs were sutured using 10-0 nylon thread and were used as a model of canal plugging. Compound action potentials (CAPs) of the PSC nerve evoked by a cooling stimulus were recorded. The CAPs after suturing the PSCs were found to be greater than those before suturing. This indicates that the fluid shift effect increases after canal suturing. Additionally, we present a clinical case in which caloric nystagmus was observed after lateral canal plugging. In this case MRI revealed the fluid space from the plugged portion toward the ampulla to be intact. There was another case with lateral canal plugging that showed the same findings on MRI. The above findings support the hypothesis that fluid shift is responsible for the caloric response without the convective flow of endolymph in the plugged canal.

Action Potentials↗
PubMed1991

Effects of hydrostatic pressure on sensory discharge in frog semicircular canals.

The effects of endolymphatic and perilymphatic pressure changes on resting and mechanically evoked responses were studied in isolated posterior semicircular canals of the frog. The results demonstrated that ampullar receptors are extremely sensitive to hydrostatic pressure changes (0.25 mm H2O were sufficient to produce distinct changes), being inhibited by endolymphatic pressure increases and facilitated by perilymphatic ones. Intracellular recordings from single afferent axons showed that the effects of hydrostatic pressure result from a modified transmitter release from the synaptic pole of the hair cells. Unlike resting activity, mechanically evoked activity was always depressed in the presence of a hydrostatic pressure. This indicates that the sensitivity of ampullar receptors to mechanical stimuli, i.e. the gain of the conversion process, is maximal when no pressure is present between the inner and the outer fluid. The possible action of hydrostatic pressure on vestibular receptors is discussed.

Afferent Pathways↗
PubMed2005

Diagnosis and management of lateral semicircular canal benign paroxysmal positional vertigo.

OBJECTIVE: Describe the diagnosis, treatment, and outcome of a group of 20 patients with lateral semicircular canal benign paroxysmal positional vertigo (LSC-BPPV). STUDY DESIGN AND SETTING: Retrospective review of 20 patients with LSC-BPPV (10 with geotropic and 10 with apogeotropic nystagmus) presenting to a tertiary balance center. Diagnosis was confirmed with infrared nystagmography in Dix-Hallpike positioning tests and supine positional tests. Patients were treated with one or more particle repositioning maneuvers. RESULTS: Addition of supine positional nystagmus tests to Dix-Hallpike positioning testing improves sensitivity in the diagnosis of LSC-BPPV. Treatment outcomes in the apogeotropic LSC-BPPV group were poorer than the geotropic LSC-BPPV group. SIGNIFICANCE: Adding supine positional testing to routine vestibular diagnostic testing will increase the identification of LSC-BPPV. Apogeotropic LSC-BPPV is more challenging to treat.

Adult↗
PubMed2002

Relationship between inner-ear fluid pressure and semicircular canal afferent nerve discharge.

The present study was designed to determine (1) the transcupular fluid pressure (deltaP) generated across the semicircular canal cupula in response to sinusoidal head rotation, (2) the translabyrinthine dilational pressure (P0) generated across the membranous labyrinth in response to an increase in endolymph fluid volume (hydrops), (3) afferent nerve discharge patterns generated by these distinct pressure stimuli and, (4) threshold values of deltaP and P0 required to elicit afferent neural responses. The experimental model was the oyster toadfish, Opsanus tau. Micromechanical indentation of the horizontal canal (HC) duct and utricular vestibule was used to simulate sinusoidal head rotation and fluid volume injection. Single-unit neural spike trains and endolymph pressure within the ampulla, on both sides of the cupula, were recorded simultaneously. deltaP averaged 0.013 Pa per 1 degrees/s of sinusoidal angular head velocity and P0 averaged 0.2 Pa per 1 nL of endolymph volume injection. The most responsive afferents had a threshold sensitivity to deltaP of 10(-3) Pa and to P0 of 5 x 10(-2) Pa based on a discharge modulation criterion of 1 impulse/s per cycle for 2 Hz pressure stimuli. Neural sensitivity to AP was expected on the basis of transverse cupular and hair bundle deflections. Analysis of mechanics of the end organ, neuronal projections into the crista, and individual neural firing patterns indicates that P0 sensitivity resulted from pressure-induced distension of the ampulla that led to a nonuniform cupular deformation pattern and hair bundle deflections. This explanation is consistent with predictions of a finite element model of the end organ. Results have implications regarding the role of deltaP in angular motion transduction and the role of P0 under transient hydropic conditions.

Action Potentials↗
PubMed2003

The click-evoked vestibulo-ocular reflex in superior semicircular canal dehiscence.

The authors studied eye movement responses to loud (110dB) clicks in 4 patients with Tullio effect due to superior semicircular canal dehiscence and in 9 normal subjects, by averaging the electro-oculogram. All 4 patients had small (0.1-0.3 deg) but easily reproducible vertical vestibulo-ocular reflex eye movement responses to the clicks. Normal subjects had responses that were at least 10 times smaller. The click-evoked vestibulo-ocular reflex test is a simple, robust way to screen dizzy patients for symptomatic superior semicircular dehiscence.

Acoustic Stimulation↗
PubMed2001

Is the pathology of horizontal canal benign paroxysmal positional vertigo really localized in the horizontal semicircular canal?

In order to clarify the pathological localization of horizontal canal benign paroxysmal positional vertigo (HC-BPPV), we performed 3D analysis of positional nystagmus in 11 patients with HC-BPPV. In addition, these results were compared with 3D analysis data of pressure nystagmus in patients with HC fistula. 3D analysis of nystagmus was carried out using a video image analysis system. In seven patients with HC-BPPV, the velocity vectors were well aligned with the axes of the HC and in four patients they were not. In addition, the 3D velocity vectors of the slow phase of pressure nystagmus in all 11 subjects with HC fistula were closely aligned with the axes of the HC. The pathology of HC-BPPV in most patients with apogeotropic positional nystagmus has been considered to be localized in the HC. However, our results strongly suggest that the pathology of HC-BPPV with geotropic nystagmus is localized in the utricle. This is the first report concerning the pathological localization of HC-BPPV based on physiological evidence.

Female↗
PubMed1980

Axonal branching in the trochlear and oculomotor nuclei of single vestibular neurons activated from the posterior semicircular canal nerve in the cat.

Axonal branches of single vestibular neurons activated by stimulation of the ampullary nerve of the posterior semicircular canal in the cat were studied by means of local antidromic stimulation in the trochlear and the oculomotor nucleus. These vestibulo-ocular neurons were located in the rostral half of the descending vestibular nucleus and the lateral part of the medial vestibular nucleus. The majority of vestibulo-ocular neurons projecting to the inferior rectus motoneuron pool in the contralateral oculomotor nucleus was activated antidromically from the contralateral trochlear nucleus as well. This suggests that axonal branches of a single vestibular neuron project to both nuclei.

Action Potentials↗