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PubMed1998

[Repositioning maneuver in benign paroxysmal vertigo of horizontal semicircular canal].

The introduction of the Lempert or Baloh "barbecue" maneuver in clinical practice has resolved many cases of paroxysmal positional vertigo of the horizontal semicircular canal. Unfortunately, this maneuver is rather difficult to perform in elderly or overweight patients and in those with reduced mobility. In such cases the Vannucchi "forced position" is the maneuver of choice. Diagnostic confirmation is, however, still a problem. The authors feel diagnosis is only confirmed when the positional nystagmus has been converted, inverted or disappears after the physical therapy maneuver. For this reason another maneuver has been developed and is described in the present work. Between May 10th and November 28th 1997 thirty cases of horizontal canalolithiasis were seen: 19 in the right vestibule, 11 the left vestibule (9 males, 21 females; age range 20 to 82 years). Of these cases, 24 (4 apogeotropic, 20 geotropic) were treated with a maneuver differing from the barbecue maneuver. Some parts of this maneuver are similar to the Semont maneuver, moving the patient from a seated position to a position on the right or left side, depending the pathology and type of vertigo (geotropic/apogeotropic). A favorable outcome was achieved in 22 cases and there was no result in 2 cases. The two non-responsive patients were then treated with forced positioning which resolved the condition. Benign paroxysmal positional vertigo from horizontal canalolithiasis responds to treatment with the above-mentioned maneuver.

Adult↗
PubMed1995

Indirect evidence for the presence and physiological role of endogenous extracellular ATP in the semicircular canal.

Previous studies have shown that low concentrations of exogenous ATP, added to the perilymphatic fluid, could modify the bioelectrical activity of the isolated semicircular canal of the frog (Rana pipiens). To test the hypothesis that ATP is endogenously present and active in the perilymphatic fluid, the influence of two ATP-purinoceptor antagonists, Reactive Blue 2 and suramin, and of the enzyme, nucleotide pyrophosphatase, were examined. When applied by perilymphatic bath substitution, the three compounds reduced, in a dose-dependent manner, the firing of the afferent fibers monitored in the absence of mechanically-applied stimulation. The response of the afferent fibers, recorded when the sensory cells were mechanically inhibited, was also reduced. No modification of the response of the excitatory phase of the mechanical stimulus was observed in the presence of the two antagonists. In contrast, the signal was significantly reduced by the enzyme. None of the three compounds exhibited an influence on the transepithelial potential, or its variation in response to mechanical stimulation. The ATP-induced modification of the firing rate of the afferent fibers, monitored in the absence of mechanical stimulation, was reduced in the presence of the three drugs. No influence of Reactive Blue 2 and suramin was observed on the increase of the spontaneous firing induced by carbachol. In contrast, the effect of carbachol was decreased by nucleotide pyrophosphatase. The excitatory influence of glutamate on the spontaneous firing was not modified by Reactive Blue 2, while it was slightly increased by suramin and nucleotide pyrophosphatase.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1985

Central projections of primary vestibular fibers in the bullfrog. III. The anterior semicircular canal afferents.

A study was made of the projection patterns in the vestibular nuclei of primary afferent fibers innervating the crista of the anterior semicircular canal (ASC) of the bullfrog. Individual neurons were intracellularly recorded to characterize their spontaneous activity and injected with horseradish peroxidase to visualize their central and peripheral projections. A quantitative evaluation was made of the lengths of the central projections of primary afferents in the various vestibular nuclei and of the number of branch terminals and their precise locations in each of the major vestibular projection areas in the brain stem. The differences between the central projection patterns of the two types of primary afferent fibers were documented: the thick fibers with their irregular spontaneous activity and the thin fibers with their more regular spontaneous activity. Each neuron sends many terminals to various vestibular nuclei. The ventral part of the ventral nucleus receives the greatest number of terminals from fibers of all sizes. The medial nucleus receives terminals from the thin fibers only, while the reticular formation receives terminals exclusively from the thick fibers. All the vestibular nuclei receive innervation from ASC afferents, with considerable overlap in areas of innervation between fibers of different caliber. Differences were found between the thick and thin fibers in their locations, their patterns of branching, and the appearance of their terminal boutons. These anatomic characteristics are interpreted to represent physiologic differences in the production of reflexes by thick and thin neurons. It is also postulated that these different neurons play different roles in vestibular system function: thick neurons contribute to the maintenance of equilibrium during movement while thin neurons participate in the maintenance of posture and vestibular tonus.

Animals↗
PubMed1991

Morphological correlates of response dynamics and efferent stimulation in horizontal semicircular canal afferents of the toadfish, Opsanus tau.

1. We used the intraaxonal labeling technique to study correlations between the terminal dendritic morphology of horizontal semicircular canal primary afferents and their response dynamics to sinusoidal head rotation and combined electrical stimulation of central efferent vestibular neurons. Thirty-eight canal afferents were identified by their sensitivity and phase of response to rotation between 0.1 and 1.0 Hz (+/- 10 degrees/s) and were subsequently labeled with horseradish peroxidase or biocytin. The afferent's dendritic field and synaptic specializations in the neuroepithelium of the crista were examined under light microscopy. 2. Rate and regularity of background discharge of the afferent were not correlated with its axon diameter or relative location of its dendritic field in the crista. 3. Response sensitivity of the afferent to rotation was correlated both with the relative location of its dendritic field in the crista and with the number of terminal endings it possesses. Afferents having low sensitivities, slow dynamics, and few terminal endings supply the peripheral portions of the crista; afferents with higher sensitivities, faster dynamics, and greater number of terminal endings supply the more central portions. It is suggested that the differences in sensitivity among the afferents reflect principally the variations in both the cupular dynamics along the crista and the number of possible hair cell contact sites in the neuroepithelium. 4. Response phase of the afferent was correlated only with the extent of its dendritic processes along the transverse axis of the crista. Afferents having transversely oriented dendritic fields had less phase lags relative to acceleration than did those having a more longitudinally oriented dendritic field. 5. Efferent stimulation produced a change in both the afferent's discharge rate and its response sensitivity to rotation. Afferents discharge rate and its response sensitivity to rotation. Afferents having a centrally located dendritic field and acceleration afferents, defined by their response to rotation, were the most affected by efferent stimulation. These results suggest that efferent innervation is either directed toward, or most efficacious in, the central regions of the crista and that it may select specific hair cell-afferent complexes.

Animals↗
PubMed1995

[Effect of streptomycin placing in the fenestra of semicircular canals on the function and morphology of the normal and hydropic ears in guinea pigs].

The effect of streptomycin placed in the fenestra of lateral semicircular canal (LSC) on the function and morphology of the normal and artificial hydropic inner ears in guinea pigs was studied in order to explore the method and possibility of treating Meniere's disease by using aminoglycosides. After placing the drug in the fenestra of LSC, no change in AP threshold of ECochG in normal ears but an increase of that in hydropic ears were found caloric induced nystagmus in both groups were disappeared. Under light microscope, severe damage of vestibular epithelium of three canal cristae and utricular macula was noted, while no insult of cochlear hair cells was found in normal ears. More severe damage of vestibular epithelium with part of them degenerated and atrophied and lesions of cochlear hair cells in basal turns and part of second turns occurred in hydropic ears. These demonstrated that the ototoxicity of streptomycin was higher in hydropic ears than in normal ears. In order to destroy vestibular function and preserve cochlear function, further study for adequate dosage of streptomycin and correct route of administration is needed.

Animals↗
PubMed1990

Localization and synaptic effects of inhibitory vestibulocollic neurons activated by the posterior semicircular canal nerve in the cat.

Cellular locations, axonal projections, and synaptic effects of inhibitory vestibulocollic (VC) neurons activated by the ampullary nerve of the posterior semicircular canal (PCN) were studied in anesthetized cats. The inhibitory VC neurons were identified by their monosynaptic responses to PCN stimulation and by their antidromic responses to stimulation of the ipsilateral (i-) and contralateral (c-) neck extensor motoneuron pools, which are inhibitory targets of the PCN. They were classified as VCi (vestibulocollic neuron sending an axon to the i-neck extensor motoneuron pool) and VCc (vestibulocollic neuron sending an axon to the c-neck extensor motoneuron pool) neurons. Neither VCi nor VCc neurons were activated antidromically by localized stimulation of the ascending medial longitudinal fasciculus (asc. MLF) or the 3rd nuclei. Their cell somata were localized in the rostral part of the descending vestibular nucleus and the ventral part of the lateral vestibular nucleus. VCi and VCc neurons produced unitary IPSPs in neck extensor motoneurons in the C1 segment.

Action Potentials↗
PubMed2005

Vitamin D upregulates expression of ECaC1 mRNA in semicircular canal.

The low luminal Ca2+ concentration of mammalian endolymph in the vestibular labyrinth is required for normal balance. We found transcripts in primary cultures of semicircular canal duct (SCCD) epithelial cells from neonatal rats representing a complete transport system for transepithelial absorption of Ca2+ that is comprised of the epithelial Ca2+ channels ECaC1 (CaT2, TRPV5) and ECaC2 (CaT1, TRPV6), calbindin (calbindin-D9k, calbindin-D28k), Na+/Ca2+ exchanger (NCX1, NCX2, and NCX3), and plasma membrane Ca2+-ATPase (PMCA1, PMCA3, and PMCA4) by RT-PCR. Further, vitamin D receptor was also expressed in SCCD and it was found by quantitative RT-PCR that incubation for 24 h with 1,25-dihydroxyvitamin D3 upregulated the expression of ECaC1, calbindin-D9k, and calbindin-D28k. These observations provide evidence for the first time of an ECaC-based Ca2+ transport system in SCCD that could maintain the low Ca2+ concentration in vestibular endolymph.

Animals↗
PubMed2005

Abnormal mesenchymal differentiation in the superior semicircular canal of brn4/pou3f4 knockout mice.

OBJECTIVE: To examine the developmental time course of the mutant phenotype and cellular mechanisms that result in malformations of the superior semicircular canal (SSCC) in Brn4 knockout mice. Mutations in the Brn4/Pou3f4 gene result in characteristic inner ear abnormalities in mutant mouse pedigrees, and the findings in these mice are similar to those in human X-linked deafness type III. DESIGN: Mutant and control mice were killed at various neonatal time points to assess the development of the SSCC. Measurements of SSCC diameter were made on paint-perfused specimens at postnatal day (P) 0, P7, P10, and P14. Histologic evaluation of the SSCC was made on hematoxylin-eosin-stained sections at P10. RESULTS: A dysmorphic constriction of the superior arc of the SSCC in Brn4 knockout mice was initially detectable at P14. Interestingly, the mutant SSCC is indistinguishable from control mice at earlier neonatal time points. In mutant neonates, there is persistence of immature woven bone with high cellularity surrounding the perilymphatic space of the SSCC. These findings are not present in control animal specimens, which demonstrate appropriate lamellar bony architecture. CONCLUSIONS: In Brn4 knockout mice, constriction of the SSCC with narrowing of the bony labyrinth develops in the postnatal period at approximately P14. The persistence of immature bone in affected mice indicates that signaling abnormalities disrupt normal mesenchymal differentiation in the SSCC.

Animals↗
PubMed1998

Acute effects of semicircular canal destruction on the cochlea, with and without preceding Pseudomonas aeruginosa exotoxin A treatment.

Acute electrophysiological and morphological changes in the cochlea following destruction of the semicircular canals (SCCs) were investigated to elucidate differences in cochlear vulnerability to surgical procedure under two conditions: normal healthy condition and a pathological condition induced by Pseudomonas aeruginosa exotoxin A (PaExoA). Frequency-specific auditory brainstem response recording and examination by light microscopy (LM) and scanning electron microscopy (SEM) were performed in the acute stage, immediately following, and 2, 5, and 10 days after the intervention. All normal healthy rats showed noticeable hearing loss immediately after the operation, predominantly in lower frequency areas, followed by complete recovery within 5 days. LM revealed rupture and slight distension of Reissner's membrane. SEM revealed considerable disarray of the stereocilia, especially on the outer hair cells (OHCs) of the third row in the upper half-turns of the cochlea. By contrast, all rats under pathological conditions showed delayed and incomplete hearing recovery from postoperative hearing loss. LM revealed various kinds of cochlear reaction, such as distension of Reissner's membrane, infiltration of inflammatory cells into the cochlea, and severe inflammatory change. Damage both of inner hair cells in the basal turn and of OHCs in the upper half-turns was more noticeable, compared with that under normal conditions. These findings indicate that SCC destruction under pathological conditions induced by PaExoA is detrimental to postoperative hearing recovery, even if the preoperative hearing level had appeared electrophysiologically normal.

ADP Ribose Transferases↗
PubMed1978

Frequency-response analysis of vestibular-induced neck reflex in cat. I. Characteristics of neural transmission from horizontal semicircular canal to neck motoneurons.

1. Vestibular-induced neck muscle reflexes (vestibulocollic reflexes) were studied with frequency-response methods in unanesthetized, decerebrate cats. The horizontal semicircular canals were stimulated by oscillation of the turntable and EMG activity was recorded from neck extensor muscles. 2. The maximum firing rate of each motor unit was less than 40 spikes/s. The motor units were classified by their maximum firing rates into two groups: HF (high frequency) units which could fire above 20 spikes/s and LF (low frequency) units which could not exceed 20 spikes/s of firing. The HF units had larger gains than the LF units on the average. 3. Compound EMGs, which presumably represent activity of the whole muscle, were examined at different frequencies of stimulation. The gain of compound EMG responses depended on the spontaneous activity. When the spontaneous activity was low or too high, the gain was small. There was an intermediate spontaneous activity level at which the gain became maximal. 4. The phase lag and the gain of the frequency response were represented in a Bode diagram with respect to angular acceleration. The transfer function of the system from the vestibular nuclei to neck EMG activity was estimated by assuming a first-order lag-lead system. A phase lag of 70-80 degrees (0.05 Hz) was found between the averaged activity of vestibular nucleus neurons and cervical motor activity. A positive correlation was observed between the phase lag and the gain of each motor unit. These results cannot be attributed solely to the action of the vestibulospinal tract, but suggest the existence of a neural intergrator in the vestibulocollic reflex arc.

Action Potentials↗
PubMed2003

CT evaluation of bone dehiscence of the superior semicircular canal as a cause of sound- and/or pressure-induced vertigo.

PURPOSE: To describe the computed tomographic (CT) findings at different collimation widths associated with superior semicircular canal (SSC) dehiscence syndrome and to determine the frequency of these findings in a control population. MATERIALS AND METHODS: Temporal bone CT scans with 1.0-mm and/or 0.5-mm collimation were obtained in 50 patients with sound- and/or pressure-induced vestibular symptoms. The control population consisted of 50 patients undergoing CT at 1.0-mm collimation and 57 patients undergoing CT at 0.5-mm collimation for other reasons. RESULTS: SSC dehiscence was documented on CT scans in all 36 patients with the clinical syndrome, with bilateral findings in six patients. Six other patients without specific clinical signs appeared to have dehiscence on 1.0-mm-collimated scans. Intact bone overlaying the SSC was subsequently identified with 0.5-mm-collimated CT in each case. On the 1.0-mm-collimated scans in 50 control patients, an area judged as possible or definite dehiscence was identified in 18 of 100 ears. The bone overlaying the SSC was intact in each of the 114 control ears evaluated with 0.5-mm-collimated CT. CT findings from the patients with vestibular symptoms combined with those in the control population indicated that the positive predictive value of an apparent dehiscence in the diagnosis of SSC dehiscence syndrome improved from 50% with 1.0-mm-collimated CT with transverse and coronal images to 93% with 0.5-mm-collimated CT with reformation in the plane of the SSC. CONCLUSION: The positive predictive value of CT in identification of SSC dehiscence syndrome improves with 0.5-mm-collimated helical CT and reformation in the SSC plane.

Adolescent↗
PubMedDate not supplied

Lack of evidence of an interaction between leu-enkephalin and muscarinic-like responses in the frog semicircular canal.

Using multiunit recording of action potentials from the whole vestibular nerve, we studied whether opioid peptide leu-enkephalin (Enk) may modulate muscarinic-like responses in semicircular organs of the frog. When acetylcholine (ACh) (0.1-1 mM) was applied with 1 nM Enk, the maximal frequency increase induced by ACh was reduced.However,the frequency decrease of ACh responses under Enk did not differ from the frequency decline in basal spike discharge induced by Enk alone. Administration of atropine (1 microM) left the response to Enk intact and blocked the excitatory effect of ACh. No modification of the ACh response under Enk was observed in the presence of the non-selective opioid receptor antagonist naloxone (10 microM). This study suggests that no interaction exists between the ACh-mediated excitatory action on resting activity in the isolated semicircular canal preparation and the suppressive action of Enk.

Acetylcholine↗
PubMed2005

Self-treatment for benign paroxysmal positional vertigo of the posterior semicircular canal.

The authors compared the efficacy of the Epley procedure with and without self-treatment in 80 patients with benign paroxysmal positional vertigo of the posterior semicircular canal. The self-treatment group (88%) had better results than the Epley-alone group (69%) based on both symptoms and nystagmus (p = 0.048). Complications occurred in 2.6% of the Epley-alone group and in 7.5% of the self-treatment group (p = 0.62).

Adult↗
PubMed2000

Semicircular canal occlusion causes permanent VOR changes.

We measured the guinea pig horizontal vestibulo-ocular reflex (hVOR) to high acceleration impulsive head rotations following a unilateral lateral semicircular canal (LSCC) occlusion. We found a significant hVOR deficit for rotations toward the side of the occluded LSCC and this deficit did not show systematic changes over 3 months. We considered the LSCC nerve was still functional as shown by the normal appearance of the crista of the LSCC ampulla and also electrical stimulation of the LSCC. We conclude that the VOR during angular acceleration in response to high acceleration shows no adaptive plasticity following a unilateral LSCC occlusion.

Animals↗
PubMed2005

The effect of canalith repositioning for anterior semicircular canal canalithiasis.

The purpose of this study was to evaluate the efficacy of our canalith repositioning procedure (CRP) for benign paroxysmal positional vertigo (BPPV) of the anterior semicircular canal (ASC). We conducted a prospective study of 30 ASC BPPV patients to analyze the efficacy of a modified CRP. When the patient was diagnosed as having ASC BPPV by a specific provocative positioning test, a CRP was performed. The response to the treatment was categorized as grade I-IV. Of the 30 study patients, 6 were male and 24 were female with the highest incidence when the patients were in their 50s. The vertigo and nystagmus in 29 patients fully resolved (grade I). Using this maneuver, 96.7% of patients became symptom free. Overall, the maneuver needed to be performed 1.97 times to control the symptoms. Based on these findings, CRP could be one of the most effective treatment methods for ASC BPPV.

Adult↗
PubMed2006

Benign paroxysmal positional vertigo due to a simultaneous involvement of both horizontal and posterior semicircular canals.

From April 2001 to November 2003, we investigated 8 patients with benign paroxysmal positional vertigo (BPPV) that was suspected to simultaneously affect both the horizontal and posterior semicircular canals (HSCC and PSCC). These cases showed typical vertical-torsional nystagmus induced by the Dix-Hallpike maneuver, followed by a horizontal nystagmus. They also showed a direction-changing geotropic or apogeotropic positional nystagmus triggered by lateral head rotations in the supine position. Using the three-dimensional analysis of the positional nystagmus, the rotation axis of the positional nystagmus had a component perpendicular to the plane of PSCC and another component perpendicular to the plane of HSCC. All these findings suggest that BPPV in these patients was a combination of posterior and horizontal canal BPPV. The observation of a vertical-torsional positional nystagmus should prompt the specialist to perform not only the canalith repositioning procedure, but also to execute lateral head turns in the supine position.

Adult↗