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PubMed1985

Fenestration of the horizontal semicircular canal in congenital conductive deafness.

Fenestration of the horizontal semicircular canal enables the otologic surgeon to restore hearing in those patients with congenital conductive deafness who are not candidates for stapedectomy, ossicular reconstruction, or tympanoplasty. Since the development of stapedectomy, much of the finesse technique of fenestration surgery has been lost, and many otologic surgeons today are unfamiliar with the fenestration operation. The surgical technique for creating a permanently patent fenestra in the horizontal semicircular canal is described. The causes of failure in fenestration surgery are reviewed. Thirty-three patients who have undergone fenestration for congenital conductive deafness over a 30-year period, and 100 patients who underwent fenestration for otosclerosis in 1950, are reviewed to demonstrate patient selection and the efficacy of this operation in establishing long-term hearing improvement.

Adolescent↗

PubMed1992

Secretion of endolymph by the isolated frog semicircular canal.

Secretion of endolymph is localized in some structures of the inner ear, namely the stria vascularis in the cochlea and the dark cells in the vestibule and in the lower vertebrate inner ear. In isolated semicircular canal it is possible to study separately the endolymphatic composition in the ampulla, which contains the dark cells, and in its non-ampullar part, which is devoid of these cells. Further, in vitro preparation of the semicircular canal provides access to both faces of the epithelium so that different agents can be applied separately to the apical or to the basolateral membranes of the epithelium. In this structure, the following results were obtained: i) in vitro, the semicircular canal secreted a K-rich, positively polarized fluid; ii) this fluid was secreted only in the ampulla of the semicircular canal; iii) the secretion of endolymph was dependent on basolateral Na+, K(+)-ATPase, inhibited by ouabain, and basolateral Na-K-Cl co-transporter, inhibited by bumetanide; iv) approximately 60% of luminal Na absorption occurred across a luminal Na channel inhibited by amiloride; v) the permeability of the paracellular pathway of the semicircular canal epithelium was 7.10(-7) cm/s. These results indicate that endolymph secretion involves basolateral Na+, K(+)-ATPase and Na-K-Cl co-transporter. An Na channel has been shown at the apical membrane.

Animals↗

PubMed2006

Mondini-like malformation mimicking otosclerosis and superior semicircular canal dehiscence.

In 2003, it was reported that superior semicircular canal dehiscence can mimic otosclerosis because of low-frequency bone conduction hearing gain and dissipation of air-conducted acoustic energy through the dehiscence. We report the case of a 17-year-old girl with left-sided combined hearing loss thought to be due to otosclerosis. Bone conduction thresholds were -10 dB at 250 and 500 Hz and she had a 40 dB air-bone gap at 250 Hz. When a tuning fork was placed at her ankle she heard it in her left ear. Acoustic reflexes and vestibular evoked myogenic potentials could be elicited bilaterally. Imaging of the temporal bones showed no otosclerosis, superior semicircular canal dehiscence or large vestibular aqueduct, but a left-sided, Mondini-like dysplasia of the cochlea with a modiolar deficiency could be seen. Mondini-like cochlear dysplasia should be added to the causes of inner-ear conductive hearing loss.

Adolescent↗

PubMed2005

Canalolithiasis of the superior semicircular canal: an anomaly in benign paroxysmal vertigo.

According to the canalolithiasis theory, benign paroxysmal vertigo (BPPV) is caused by gravity-dependent movements of otoconial debris that collects in the endolymph of the posterior semicircular canal. Other parts of the vestibular organ are rarely affected, and it is mainly the horizontal canal that is affected by this atypical form of BPPV. Canalolithiasis of the superior semicircular canal must be considered an anomaly because the superior semicircular canal is the highest point of the vestibular organ and debris normally cannot collect in this special location. Until now, BPPV of the superior canal has mainly been dealt with theoretically in the literature. The authors present three patients with canalolithiasis of the superior semicircular canal and offer direct proof of the condition using high-resolution 3D MRI.

Adult↗

PubMed2005

[Benign paroxysmal positional vertigo of the anterior semicircular canal: clinical aspects and treatment].

OBJECTIVE: To describe the videonystagmographic characteristics and the treatment of the patients reached with a canalolithiasis or a cupulolithiasis of the anterior semicircular canal. MATERIAL AND METHOD: Retrospective study concerning patients treated for a Benign Paroxysmal Positional Vertigo (BPPV) of the anterior semicircular canal. Each patient after analysis under videonystagmoscopy (VNS) and under videonystagmography (VNG) was treated by maneuvers. RESULTS: On 462 observations of typical BPPV 6 cases of VPPB of the anterior semicircular canal were treated concerning 5 patients (1.3%). CONCLUSION: The BPPV of the anterior semicircular canal are rare. We modified our method of diagnosis, and our therapeutic techniques could be validated with the help of the two-dimensional videonystagmography.

Electronystagmography↗

PubMed2003

Spatial tuning and dynamics of vestibular semicircular canal afferents in rhesus monkeys.

Rotational head motion in vertebrates is detected by the three semicircular canals of the vestibular system whose innervating primary afferent fibers encode movement information in specific head planes. In order to further investigate the nature of vestibular central processing of rotational motion in rhesus monkeys, it was first necessary to quantify afferent information coding in this species. Extracellular recordings were performed to determine the spatial and dynamic properties of semicircular canal afferents to rotational motion in awake rhesus monkeys. We found that the afferents innervating specific semicircular canals had maximum sensitivity vectors that were mutually orthogonal. Similar to other species, afferent response dynamics varied, with regular firing afferents having increased long time constants ( t(1)), decreased cupula velocity time constants ( t(v)), and decreased fractional order dynamic operator values ( s(k)) as compared to irregular firing afferents.

Action Potentials↗

PubMed1996

Four convergent patterns of input from the six semicircular canals to motoneurons of different neck muscles in the upper cervical cord.

This study was performed to investigate the pattern of input and the pathways from the six semicircular canals to motoneurons of various neck muscles in anesthetized cats. Intracellular postsynaptic potentials from neck motoneurons were recorded in response to electrical stimulation of the six ampullary nerves. The results showed that motoneurons of a particular neck muscle have a homogeneous convergent pattern of input from the six semicircular canals; there are four patterns of input from the six semicircular canals to motoneurons of various neck muscles; and the trisynaptic connection between the semicircular canal nerves and neck motoneurons was identified in addition to the disynaptic connection.

Action Potentials↗

PubMedDate not supplied

Responses of frog vestibular neurons to combined temperature microstimulation of the semicircular canals.

The temperature microstimulation of the semicircular canal (heat bursts lasting about 2 sec with a peak amplitude of 0.5-5.0 degrees C) can be regarded as an analog of angular acceleration acting within the cavity of the given canal; the combination of temperature microstimulations targeted simultaneously on several canals can serve as a physical model of accelerated rotation having complex spatial characteristics. The recording of the activity of neurons of the vestibular nuclei of the frog (n = 278) in response to temperature microstimulation of the canals showed that 80% of the neurons have inputs from one to two canals and only 20% from three to six canals. The distribution of laterality was characterized by the predominance of ipsilateral inputs: 201 neurons (72.3%) had only ipsilateral inputs; 14 neurons (5%) had only contralateral inputs; 63 neurons (22.7%) had both inputs. The ipsilateral horizontal (67.6%) and the posterior (61.9%) were the most effective inputs; while among the contralateral, the posterior (21.2%) canals were the most effective; the least effective were the contralateral horizontal (8.6%) and the anterior (5.0%) canals. The presence of latent canal inputs (both excitatory and inhibitory) which showed up in combination with effective inputs was demonstrated.

Animals↗

PubMed2001

Perspectives for the comprehensive examination of semicircular canal and otolith function.

A review is presented on the three-dimensional aspects of the vestibulo-oculomotor system and the current functional tests for unilateral examination of the individual receptors in the vestibular labyrinth. In the presentation, attention is directed towards the recently developed vestibular tests, which promise a more comprehensive examination of labyrinth function. More explicitly, unilateral tests for the utricle, saccule and the individual semicircular canals are discussed. Caloric irrigation and rotatory testing are widely used as tests for the integrity of the (horizontal) semicircular canals. Little useful diagnosis is made however on the vertical canals, not to mention the otolith organs. A promising approach to the examination of individual semicircular canal function has been described. This involves the perception of self-rotation in each of the planes of the semicircular canals. The patient/subject is rotated by an arbitrary amount on a standard Barany chair and then required to return the chair to its original position, by joystick control of the chair velocity. In order to test the vertical canals, the head of the subject/patient is positioned so that the plane of each canal lies in the plane of rotation. A promising unilateral test of saccular function involves the use of vestibular evoked myogenic potentials. Here it has been demonstrated that the saccules can be activated using brief, high-intensity acoustic clicks. The myogenic potential is measured using surface electrodes over the sternocleidomastoid muscles. Initial data from patients has indicated that the test is specific for unilateral saccule disorders. The unilateral test of utricle function is based on the eccentric displacement profile. Thus, eccentric displacement of the head to 3.5 cm during constant velocity rotation about the earth-vertical axis generates an adequate unilateral stimulation of the otolith organ, without involving the semicircular canals. This paradigm has also proved efficient in localizing peripheral otolith dysfunction by means of SVV estimation. This represents a novel test of otolith function that can be easily integrated into routine clinical testing. In contrast to the otolith-ocular response, the subjective visual vertical also reflects the processing of otolithic information in the higher brain centres (thalamus, vestibular cortex). Exploitation of the two complementary approaches therefore provides useful information for both experimental and clinical scientists. Of direct interest is the finding that testing with the subject rotating on-centre is sufficient to localize peripheral otolith dysfunction by means of SVV estimation. This represents a novel test of otolith function that can be easily integrated into routine clinical testing. In addition to caloric testing, which has remained the classical unilateral test of vestibular function, the newly developed tests should improve the differential diagnosis of vestibular disorders.

Caloric Tests↗

PubMed1990

Interaction of excitatory and inhibitory stimuli on the action potential of the semicircular canal in the frog.

The posterior semicircular canal of the frog was sinusoidally stimulated by mechanical endolympathic flow. Interaction of the excitatory and the inhibitory responses was analyzed on the spike density histogram. When the oscillation started in ampullofugal direction, the evoked action potentials were readily suppressed by the following ampullopetal stimulus. When the oscillation started in ampullopetal direction, the action potential appeared slowly, indicating that the inhibitory response has a longer time course than the excitatory response.

Action Potentials↗

PubMed1993

Acetylcholinesterase activity is associated with efferent endings in the sensory epithelia of the utricle and semicircular canals of the rainbow trout inner ear.

The mechanosensory hair cells of the utricle and semicircular canals of the trout inner ear are morphologically similar to type II hair cells of the avian and mammalian vestibular end organs. These cells are innervated by two types of nerve terminals. The nonvesiculated terminals are considered to be afferent, and the vesiculated endings are presumed to be efferent. The presumptive efferent endings contain numerous clear, round vesicles and a few that are dense-cored. Histocytochemical, electron microscopic analysis has localized acetylcholinesterase activity to plasma membranes of vesiculated, presumptive efferent nerve terminals in sensory epithelia of the utricle and semicircular canals. No reaction product was observed at the receptoneural synapse or found in nonvesiculated, presumptive afferent endings. Control specimens incubated in the presence of eserine sulfate, an inhibitor of acetylcholinesterase, were devoid of reaction product. These results support the tenet that vesiculated nerve endings in the sensory epithelia of the utricle and semicircular canals of the trout are cholinergic.

Acetylcholinesterase↗

PubMed1982

Postnatal developmental changes in the response of rat primary horizontal semicircular canal neurons to sinusoidal angular accelerations.

At birth primary horizontal semicircular canal afferent neurons in the albino Wistar rat have slow, irregular spontaneous activity and insensitive, sluggish, variable responses to sinusoidal angular acceleration stimuli. There are rapid changes in the gross morphology of the rat semicircular canal in the first 4-5 days after birth, and during this time there is a rapid increase in neural gain re acceleration. Irregular neurons in rats about 6 days old have gains in the same range as irregular neurons in adult rats. However, after the gross morphological growth is complete, there continues to be a decrease in phase lag re acceleration. The causes of this developmental change in phase are unknown. It could be produced by changes in the receptor-afferent-efferent complex or by changes in the cupula or cupula-hair-cell attachment. These results with sinusoidal accelerations confirm the developmental increase in sensitivity and decrease in time constant found with constant angular accelerations (Curthoys 1979b).

Acceleration↗

PubMed2001

Location of dye-coupled second order and of efferent vestibular neurons labeled from individual semicircular canal or otolith organs in the frog.

Vestibular nerve branches innervating the sensory epithelia of the three semicircular canals or of the three otolith organs of frogs were selectively labeled in-vitro with biocytin. Labeled afferent fibers from the semicircular canals, utricle, and lagena were encountered in each of the four vestibular nuclei and their projections overlapped considerably. Saccular afferent fibers projected to the dorsal (acoustic) nuclei and smaller projections to the vestibular nuclei were regionally restricted. Per semicircular canal or otolith organ about equal numbers (11-14) of medium sized vestibular neurons (between 7.5 and 17 microm in diameter) were dye-coupled to afferent fibers. Most of these dye-coupled vestibular neurons were located in the lateral and descending vestibular nuclei between the VIIIth and IXth nerves. The superior vestibular nucleus was relatively free of dye-coupled vestibular neurons. The location of this subpopulation of central vestibular neurons supports the notion that these neurons are part of a particular vestibulospinal pathway. In addition, from each of the canal and/or otolith organs about 3-4 efferent vestibular neurons were labeled retrogradely. These neurons (between 15 and 26 microm in diameter) were located ventral to the vestibular nuclear complex. The branching of efferent vestibular neurons was shown by the presence of neurons that were double labeled by two different fluorescent dyes applied in the same experiment to the anterior and posterior ramus of the same VIIIth nerve, respectively. The branching of these efferent neuron axons explained the presence of collaterals and terminals in the sensory epithelia of a number of untreated ipsilateral endorgans.

Afferent Pathways↗

PubMed1992

Changes in monkey horizontal semicircular canal afferent responses after spaceflight.

Extracellular responses from single horizontal semicircular canal afferents in two rhesus monkeys were studied after recovery from a 14-day biosatellite (COSMOS 2044) orbital spaceflight. On the 1st postflight day, the mean gain for 9 different horizontal canal afferents, tested using one or several different passive yaw rotation waveforms, was nearly twice that for 20 horizontal canal afferents similarly tested during preflight and postflight control studies. Adaptation of the afferent response to passive yaw rotation on the 1st postflight day was also greater. These results suggest that at least one component of the vestibular end organ (the semicircular canals) is transiently modified after exposure to 14 days of microgravity. It is unclear whether the changes are secondary to other effects of microgravity, such as calcium loss, or an adaptive response. If the response is adaptive, then this report is the first evidence that the response of the vestibular end organ may be modified (presumably by the central nervous system via efferent connections) after prolonged unusual vestibular stimulation. If this is the case, the sites of plasticity of vestibular responses may not be exclusively within central nervous system vestibular structures, as previously believed.

Adaptation, Physiological↗

PubMed2000

Does the vertical semicircular canal influence the subjective visual vertical?

The aim of the present study is to evaluate the influence of vertical semicircular canals on the subjective visual vertical (SVV). SVV was measured on conditions with or without the rotatory stimulus in a head-tilted position, 60 deg back-ward and then rotated 45 deg either to the right or left in 7 healthy volunteers. By this procedure, it was possible to evaluate the SVV elicited by the excitability of vertical semicircular canals. SVV was normal on the condition without the rotatory stimulus. However, SVV was abnormal on the condition with the rotatory stimulus, especially, which was much deviated during the posterior canal excited. We conclude that the vertical semicircular canal influences the spatial orientation such as the SVV.

Adult↗

PubMed1997

Ablation of posterior semicircular canal for benign paroxysmal positional vertigo.

Obstruction of the posterior semicircular canal to prevent fluid movement without injury to the neurosensory end organ has been shown to be effective treatment for benign paroxysmal positional vertigo. Risk of injury to the inner ear with loss of hearing has been reported with a variety of techniques. This paper will describe a modification of the procedure to ablate the posterior semicircular canal and to minimize the risk of inner ear injury. The procedure has been performed on 17 patients with prompt and lasting relief of vertigo and no hearing loss. The procedure seems to be a valuable and effective treatment for the disturbing condition of benign paroxysmal positional vertigo.

Adult↗

PubMed2000

["Inner perilymph fistula" of the anterior semicircular canal. A new disease picture with recurrent attacks of vertigo].

In 1998 Minor et al. described a new variant of perilymphatic fistula: the "superior canal dehiscence syndrome". This syndrome is clinically characterized by recurrent attacks of vertigo and oscillopsia induced by loud noises or stimuli that result in changes in intracranial or middle ear pressure. It is caused by a dehiscence of bone overlying the superior (anterior) semicircular canal. Due to this dehiscence, a third, mobile window (in addition to the round and oval windows) is formed, and changes in pressure are pathologically transduced to the anterior semicircular canal. Although the superior canal dehiscence syndrome is not a rare condition, no other cases have yet been reported. Therefore, we describe a typical patient who suffered for many years from recurrent attacks of vertigo and oscillopsia induced by coughing and Valsalva's maneuvers. High resolution temporal bone CT scan showed a defect in the bone overlying the left anterior semicircular canal. Three-dimensional eye movement recordings using the search coil technique and subsequent vector analysis demonstrated that the eye movements were induced by excitation of the left anterior semicircular canal. We conclude that superior canal dehiscence syndrome is an important differential diagnosis in patients suffering from symptoms of a perilymphatic fistula, especially since it can be successfully treated by "plugging" of the affected semicircular canal. Such patients are thus spared unnecessary surgery of the middle ear.

Diagnosis, Differential↗

PubMed2005

Three-dimensional reconstruction of the human semicircular canals and measurement of each membranous canal plane defined by Reid's stereotactic coordinates.

OBJECTIVES: Equations for estimating the planar relationships of the human semicircular canals were devised by Blanks et al from a dissected bony labyrinth in a human skull. However, a similar study on the membranous semicircular canal planes has never been published. METHODS: In this study, the angle between each membranous canal plane and Reid's stereotactic horizontal plane was measured on serial histologic sections of 7 temporal bones from Japanese adults. We reconstructed the 3 semicircular canals by computer-aided 3-dimensional analysis. The angles between each pair of both bony and membranous canal planes were measured. RESULTS: In the bony labyrinth, the angles between the 2 canal planes of the lateral-anterior, anterior-posterior, and lateral-posterior pairs were 90.51 degrees +/- 2.98 degrees (mean +/- SD), 91.70 degrees +/- 1.85 degrees, and 94.52 degrees +/- 3.32 degrees, respectively. The angles between the 2 membranous canal planes of the lateral-anterior, anterior-posterior, and lateral-posterior pairs were 90.05 degrees +/- 4.74 degrees, 91.03 degrees +/- 2.93 degrees, and 91.92 degrees +/- 5.22 degrees, respectively. CONCLUSIONS: The data from our study of the membranous labyrinth showed that the angles between each canal plane and the others were much closer to 90 degrees than was found by Blanks et al for the bony labyrinth.

Adult↗