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Results for “SEMICIRCULAR CANALS”

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PubMed2005

Independent effects of simultaneous inputs from the saccule and lateral semicircular canal. Evaluation using VEMPs.

OBJECTIVE: To determine the effects of stimulation of bilateral lateral semicircular canals (LSCCs) by accelerated rotation and caloric stimulation of unilateral LSCC on vestibular evoked myogenic potentials (VEMPs) in healthy volunteers. METHODS: In experiment 1, VEMPs were recorded while subjects (n = 11) were seated in a rotational chair and angular acceleration around the earth-vertical axis was provided. Amplitudes of p13-n23 were corrected using background muscle activities. In experiment 2, subjects (n = 8) in the semilateral position kept the LSCC in the vertical position and activated the sternocleidomastoid muscle by twisting the neck. After irrigating the external auditory canal with ice water, VEMPs were recorded on the irrigated side. In experiment 3, the same setting as experiment 2 was applied (n = 6), and hot water of 44 degrees C was used for irrigation. RESULTS: There were no significant differences in latencies of p13 or n23, and in corrected amplitudes by either rotatory or caloric stimulation. CONCLUSIONS: Simultaneous stimulation of LSCCs has little effect on VEMPs. SIGNIFICANCE: No functional interaction between the saccule and LSCC was detected in VEMPs, although convergence of semicircular canal and otolith nerve inputs onto single vestibular nucleus neurons has been demonstrated electrophysiologically in animal experiments.

Adult↗

PubMed1988

The otolithic origin of the vertical vestibuloocular reflex following bilateral blockage of the vertical semicircular canals in the rabbit.

The influence of bilateral plugs of the anterior and posterior semicircular canals (ASCs, PSCs) on the vertical vestibuloocular reflex (VVOR-0) of the rabbit, oscillated about the longitudinal axis maintained in a horizontal orientation, was studied. Bilateral plugs of either the ASCs or PSCs reduced the gain of the VVOR-0 evoked by stimulus frequencies above 0.005 Hz, but left a residual gain of the VVOR at higher stimulus frequencies that could be attributed to the remaining vertical canals and utricular otoliths. Bilateral plugs of both the ASCs and PSCs totally eliminated the canal component of the VVOR-0, as determined from measurements made when the animal was oriented at 90 degrees ("nose up") with respect to the earth horizontal axis, eliminating changes in the gravitational vector acting on the utricular maculae (VVOR-90). Bilateral plugs of both the ASCs and PSCs also eliminated the nonlinear increase in gain observed at intermediate frequencies in intact rabbits when oscillated about a supine orientation (VVOR-180). The contribution of the utricular otolith to the VVOR-0 in rabbits with both the ASCs and PSCs plugged was compared with the predicted otolith contribution based on the assumption of linear summation of semicircular canal and utricular signals. The assumption of linear summation appears to be incorrect. Bilateral plugs of the ASCs and PSCs increased the latency and the time constant of vertical eye movements evoked by step-roll stimulation about the longitudinal axis maintained in a horizontal orientation.

Animals↗

PubMedDate not supplied

[A model of the caloric reaction of the semicircular canals].

This paper discusses the applicability of a previously developed model of endolymph movement in the semicircular canals of the vestibular apparatus for an adequate interpretation of experimental data concerning the effect of microgravity on thermal responses of the semicircular canal.

Caloric Tests↗

PubMed1978

Fistula of the lateral semicircular canal.

The principles enunciated by Adam Politzer concerning the management of fistula of the lateral semicircular canal are as true today as they were during his time, in spite of the advances made in otologic surgery during the past 25 years or more. If a fistula of the lateral semicircular canal is suspected or proven, the patient's hearing has a greater chance of being preserved if the fistula is left undisturbed. Several illustrative cases are presented.

Adult↗

PubMed1997

Triple semicircular canal occlusion versus labyrinthectomy in the cat.

HYPOTHESIS: We have theorized that surgical occlusion of all three semicircular canals (TCO) may be an effective means to treat vestibular pathology limited to semicircular canal dysfunction while preserving hearing and otolithic function. BACKGROUND: A procedure that would eliminate vertigo while preserving hearing and minimizing postoperative dysequilibrium would be desirable. METHODS: Staged bilateral TCO was performed on four cats and compared to staged bilateral labyrinthectomy in four cats. Balance and gait analysis were performed for 3 weeks after each surgical procedure--a total of 6 weeks of testing. RESULTS: Balance testing, gait analysis, and righting reflex were found to be better among the cats undergoing TCO compared to labyrinthectomy. CONCLUSIONS: Compared to labyrinthectomy in the cat, TCO appears to have advantages for vestibular compensation after unilateral and contralateral surgery.

Animals↗

PubMed1985

Exposure and direct stimulation of the semicircular canal cupula.

The ampullary wall of the posterior semicircular canal was isolated from the frog, cut and the cupula exposed in frog Ringer's solution. The cupula was stimulated by depression with a fine glass micropipette. Three points on the cupula were selected for depression: point A, the lowest point on the midline of the cupula surface on the utricular side; point B, the uppermost on the midline of the same surface; and point C, in the middle of the lateral surface of the cupula. Depression at points A and B was toward the canal, whereas depression at point C was toward the centre of the cupula. The amount of depression was controlled by a micromanipulator. At point A, the minimum depression facilitating the posterior canal action potential was 1 micron; at point B, a greater amount of depression was needed to produce the action potential. Even a large amount of depression at point C resulted in only a small action potential, possibly because the direction of the sensory cell polarity is along the long axis of the canal.

Animals↗

PubMed1985

Effect on brainstem auditory evoked responses of posterior semicircular canal occlusion in guinea pigs.

The site of origin of benign paroxysmal positional vertigo is the posterior semicircular canal and when persistent, the condition is known as cupulolithiasis. Singular neurectomy is the current procedure of choice for the treatment of incapacitating cupulolithiasis. The neurectomy is difficult to learn and carries a significant risk of hearing loss. An alternative procedure, whereby the posterior canal is occluded, is discussed. This was performed on 11 guinea pigs and the effect on hearing was measured using brainstem evoked audiometry. Eight animals showed no hearing loss while the other three had a mild to moderate loss of hearing due to intra-operative complications. The effect of canal plugging on hearing compares favorably with the hearing results obtained with singular neurectomy. Posterior semicircular canal occlusion is suggested as a safer and technically easier treatment for incapacitating cupulolithiasis.

Animals↗

PubMed1999

Are the semicircular canals of the European mole, Talpa europaea, adapted to a subterranean habitat?

The mechanical sensitivity of vertebrate semicircular canals is directly influenced by the canal dimensions. Three key canal parameters, whose dimensions have been shown to be critical in determining the mechanical sensitivity of semicircular canals, are the streamline length, the cross-sectional area of the canal lumen and the plane area. These parameters were measured in ten specimens of adult T. europaea and compared with the dimensions of the same parameters in R. norvegicus. The major determinant of sensitivity, canal lumen area, is significantly larger in T. europaea.

Adaptation, Physiological↗

PubMed1988

A method for controlled mechanical stimulation of single semicircular canals.

In the present technical report, we describe a method of mechanical stimulation for single semicircular canals that is reproducible, sensitive, and discrete. The mechanical stimulator is capable of delivering reliable controlled stimuli of different waveforms over a wide frequency range that produce endolymph movements and consequent cupula deflections without motion being imparted to the animal. The results of electrophysiological experiments where the responses from pigeon (Columba livia) single horizontal semicircular canal afferent fibers produced by mechanical stimulation across a broad frequency bandwidth are reported. Comparisons between afferent fiber responses elicited by natural yaw rotation and mechanical stimulation were conducted, with the results indicating that the two stimulation methods produced responses from the same afferent unit that could be equated in magnitude. In addition, results are described from several control experiments that were conducted in order to determine the efficacy of the mechanical stimulation technique.

Acoustic Stimulation↗

PubMedDate not supplied

Direct influence of temperature on the semicircular canal receptor.

Effect of thermal stimulus on the vestibular receptor was studied using the isolated frog semicircular canal. The posterior (PSC) and lateral semicircular canals (LSC) were placed in the horizontal plane in frog Ringer's solution. The ampullary nerve was sucked into a glass suction electrode to record compound potentials. The steel thermal probe was positioned next to the ampullary surface to give thermal stimuli. When the PSC ampulla was cooled, the spontaneous discharge markedly increased. When the PSC ampulla was warmed, the discharge decreased. When the LSC ampulla was cooled, the discharge increased in the same manner as in the PSC. Also, warming of the LSC decreased the discharge in the same manner as in the PSC. The cupula was removed from the crista in order to eliminate the effect of volume change of the endolymph. The results were comparable to those with intact cupula in both the PSC and LSC. Cooling increased, while warming decreased the discharge. These responses are possibly due to a mechanism other than mechanical volume change, because the PSC and LSC yielded the same type of responses. Direct temperature reaction of the vestibular hair cell was suggested.

Animals↗

PubMed2004

The development of semicircular canals in the inner ear: role of FGFs in sensory cristae.

In the vertebrate inner ear, the ability to detect angular head movements lies in the three semicircular canals and their sensory tissues, the cristae. The molecular mechanisms underlying the formation of the three canals are largely unknown. Malformations of this vestibular apparatus found in zebrafish and mice usually involve both canals and cristae. Although there are examples of mutants with only defective canals, few mutants have normal canals without some prior sensory tissue specification, suggesting that the sensory tissues, cristae, might induce the formation of their non-sensory components, the semicircular canals. We fate-mapped the vertical canal pouch in chicken that gives rise to the anterior and posterior canals, using a fluorescent, lipophilic dye (DiI), and identified a canal genesis zone adjacent to each prospective crista that corresponds to the Bone morphogenetic protein 2 (Bmp2)-positive domain in the canal pouch. Using retroviruses or beads to increase Fibroblast Growth Factors (FGFs) for gain-of-function and beads soaked with the FGF inhibitor SU5402 for loss-of-function experiments, we show that FGFs in the crista promote canal development by upregulating Bmp2. We postulate that FGFs in the cristae induce a canal genesis zone by inducing/upregulating Bmp2 expression. Ectopic FGF treatments convert some of the cells in the canal pouch from the prospective common crus to a canal-like fate. Thus, we provide the first molecular evidence whereby sensory organs direct the development of the associated non-sensory components, the semicircular canals, in vertebrate inner ears.

Animals↗

PubMed2006

[Benign paroxysmal positional vertigo of the horizontal semicircular canal].

OBJECTIVE: Assesment of 8 new cases of benign paroxysmal positional vertigo of the horizontal semicircular canal (BPPV-HC), since this variant of benign positional vertigo occurs rarely. An oculographic study of features in the positional response was carried out. Electrooculograpy (EOG) allows an exhaustive study of positional nystagmus. MATERIAL AND METHODS: We have studied retrospectively 8 patients with BPPV-HC and positive head rotation manoeuvre registered by EOG techniques. Possible alterations in other EOG tests in the group of patients were analyzed. RESULTS: Most of the patients (7/8) expressed bilateral horizontal geotropic changing-direction nystagmus. One patient exhibited apogeotropic horizontal nystagmus. 5/8 cases showed caloric hypofunction. CONCLUSIONS: We have proven that BPPV-HC is an uncommon disorder. In most of the cases, provocative manoeuver generates bilateral horizontal geotropic changing-direction nystagmus that probably is due to canalitiasis of the horizontal semicircular canal. The rest, a few cases, exhibit apogeotropic horizontal response that can be secondary to cupulolitiasis or location particles in the anterior portion of the horizontal canal. A caloric test showed abnormal in many and can help to locatize the affected ear.

Adult↗

PubMed1985

The effect of glutamate on the frog semicircular canal.

L-glutamate (Glu) has at least two sites of action in the frog semicircular canal: the hair cell (presynaptic) and the primary afferent nerve fibres (postsynaptic). Glu's action on the hair cell results in an increased release of the natural transmitter which is responsible for a substantial increase in the frequency of firing in primary afferents. The presynaptic action of Glu is antagonized by D-alpha-aminoadipate (D alpha AA). Glu produces a long-lasting depolarization on the afferent nerve fibres which does not by itself elicit any afferent discharge of impulses when the release of the natural transmitter is prevented. Glu-induced nerve depolarization is only partially antagonized by D alpha AA. The difficulty of reconciling some of the observations made of the effects of Glu in semicircular canals with its presumed role as an afferent transmitter in this organ is discussed, but this role is not definitely rejected.

2-Aminoadipic Acid↗

PubMed1983

Axon collaterals to the extraocular motoneuron pools of inhibitory vestibuloocular neurons activated from the anterior, posterior and horizontal semicircular canals in the cat.

The branching pattern of inhibitory vestibuloocular neurons and their synaptic contacts with extraocular motoneurons were studied by means of spike-triggered averaging and local stimulation techniques. Individual vestibuloocular neurons activated by stimulation of the ampullary nerve of the anterior semicircular canal (ACN) inhibited motoneurons in both the ipsilateral (i-) trochlear nucleus and i-inferior rectus motoneuron pools. Individual vestibuloocular neurons receiving input from the ampullary nerve of the posterior semicircular canal (PCN) inhibited motoneurons in both the i-inferior oblique and i-superior rectus motoneuron pools. Probably, these axonal trajectories underlie conjugate eye movement during vertical head rotation. No conclusive evidence was found to indicate that single inhibitory vestibular neurons receiving input from the horizontal semicircular canal (HCN) give off axon collaterals to the i-abducens and the contralateral medial rectus motoneurons. A separate projection of HCN-related neurons to motoneurons supplying the lateral and medial rectus muscles might be useful for convergence during horizontal head movement.

Abducens Nerve↗

PubMed2006

Superior semicircular canal dehiscence with a large tegmental defect.

We report on the presentation and clinical manifestations of superior semicircular canal dehiscence in association with a large defect of the tegmen tympani in a 41-year-old woman with no previous history of trauma. Based on this case we recommend that clinicians consider the possibility of superior semicircular canal dehiscence in patients presenting with symptoms associated with tegmen defects.

Adult↗

PubMed1980

[Responses of frog primary vestibular afferents to direct vibration of a semicircular canal].

Responses of primary afferents (PA) of lateral semicircular canal to sinusoidal vibration of the canal wall were studied within the range 0.05--200 Hz (mean amplitudes 5--15 microns) in immobilized frogs. Dynamic characteristics (gain, phase) relative linear velocity of the vibrator (micron.s-1-1) were examined. At 0.2 Hz, the gain was 5.35 +/- 3.19 imp-s-1/micro.s-1 (mean; S. D.; n=14) and linearly decreased if the frequency rose. Phase lag of responses relative velocity at 0.05 Hz was 49.8 degrees +/- 16.5 degrees (n=13) and at 1 Hz 97 degrees +/- 9.4 degrees (n=22). At 100 Hz phase lag was about 240 degrees. Three groups of PA were described: wide range PA reacting in the range from 0.05 up to 60--180 Hz; high frequency PA responding in the range from 20--40 up to 100--150 Hz; low frequency PA responding in the range from 0.05 up to 2--20 Hz.

Animals↗

PubMed1989

[Electrophysiological study of ipsilateral vestibulo-collic reflex by the posterior semicircular canal stimulation].

In 12 anesthetized cats, the posterior semicircular canal nerve (PCN) stimulation evoked disynaptic EPSPs (excitatory postsynaptic potentials) in the ipsilateral neck flexor motoneurons innervating longus capitis muscles in the C1 and C2 segment (i-C1LCmn and i-C2LCmn). The mean latency and maximum amplitude of the EPSPs in the i-C1LCmn and i-C2LCmn were 1.8 and 1.9 ms, and 340 and 350 microV, respectively. Concerning the latency and amplitude of the EPSPs, there were no differences in the i-C1LCmn and i-C2LCmn. The unit activities of 9 PCN-activated vestibulo-collic neurons sending axon to the ipsilateral motoneuron pool of longus capitis muscles in the C2 segment (i-C2LCmnp) were also observed. These neurons were activated orthodromically from the PCN stimulation with latencies of 1.3ms (mean) and with latencies of 1.2ms from the i-C2LCmnp stimulation antidromically. The cell body of these vestibulo-collic neurons located in the ventrolateral part of the lateral nucleus.

Animals↗

PubMed2006

Advancement in post-meningitic lateral semicircular canal labyrinthitis ossificans.

OBJECTIVE: To assess whether lateral semicircular canal (LSCC) ossification is more advanced than that in the cochlear basal turn, in order to judge the value of the former as a predictor. METHODS: Retrospective review of 33 paediatric patients from our cochlear implant programme, with profound sensorineural hearing loss after bacterial meningitis. Magnetic resonance imaging (MRI), computed tomography (CT) scans and operative findings were reviewed. RESULTS: On CT, LSCC ossification scores were more advanced than those for the cochlear basal turn in 69.9 per cent of implanted ears. Forty-five per cent (15/33) of children had ossification at surgery. In predicting this, the sensitivity of CT LSCC ossification was 90 per cent and that of MRI LSCC ossification was 83.3 per cent. CONCLUSIONS: The more advanced ossification found in the LSCC, compared with that in the cochlear basal turn, adds to previous findings of LSCC pathology predicting cochlear ossification. Surprisingly, CT of the LSCC appears to be no less valuable than MRI in pre-operative cochlear implant assessment of post-meningitic children.

Adolescent↗