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PubMed1991

Effects of systemic and lateral semicircular canal administration of aminoglycosides on normal and hydropic inner ears.

Streptomycin was injected subcutaneously into guinea pigs (n = 12) with unilateral endolymphatic hydrops. In the unoperated ears, sensory cells were degenerated at the basal ends of all cochleas and to varying extents in the vestibular sense organs. Hydropic ears, in contrast, showed greater ototoxicity in the cochlear and saccular sensory cells, while the drug's effect on the utricular and cristae sensory cells was increased, but less remarkable. In another series of normal animals (n = 16), streptomycin was applied to a fenestra of the lateral semicircular canal. Sensory cells of all three canal cristae and utricular macula were degenerated frequently, but the sensory cells of the cochleas were rarely affected. The vestibular lesions resulting from the canal approach were greater than those produced by systemic injection. Comparison with a former gentamicin-lateral canal series revealed very little difference in action of the two drugs. However, in hydropic ears, gentamicin application to the lateral canal produced increased lesions in all sensory cells, particularly in the organ of Corti. Hydropic ears are vulnerable and a greater caution is needed in administering aminoglycosides by both the systemic and the canal route to patients with Meniere's disease.

Animals↗
PubMed2001

State-space receptive fields of semicircular canal afferent neurons in the bullfrog.

Receptive fields are commonly used to describe spatial characteristics of sensory neuron responses. They can be extended to characterize temporal or dynamical aspects by mapping neural responses in dynamical state spaces. The state-space receptive field of a neuron is the probability distribution of the dynamical state of the stimulus-generating system conditioned upon the occurrence of a spike. We have computed state-space receptive fields for semicircular canal afferent neurons in the bullfrog (Rana catesbeiana). We recorded spike times during broad-band Gaussian noise rotational velocity stimuli, computed the frequency distribution of head states at spike times, and normalized these to obtain conditional pdfs for the state. These state-space receptive fields quantify what the brain can deduce about the dynamical state of the head when a single spike arrives from the periphery.

Acoustic Stimulation↗
PubMed2004

Circling behavior in the Ecl mouse is caused by lateral semicircular canal defects.

The epistatic circler mouse (Ecl mouse) is a preexisting mutant, which displays a circling phenotype and hyperactivity. It has been shown that the circling phenotype in this mutant results from a complex inheritance pattern, but the vestibular pathology has not been analyzed. The present study deals with the morphological and functional basis responsible for the circling behavior in the Ecl mouse. Morphological examination of the inner ears revealed a bilateral malformation of the horizontal (lateral) semicircular canal and duct. No cochlear abnormalities were detected, and auditory brainstem response (ABR) measurements indicated that the auditory system is not affected. Investigation of the vestibuloocular reflex (VOR) in Ecl mice showed that their horizontal VOR on stimulation is virtually absent, which correlates with the morphological findings.

Animals↗
PubMed2004

Stimulation of the semicircular canals via the rotary chair as a means to test pharmacologic countermeasures for space motion sickness.

OBJECTIVE: Space motion sickness is currently treated pharmacologically with the empiric use of the H1 antihistamine promethazine, but use of this intervention is limited by the side effect of significant sedation. This creates a dilemma, as full cognition is particularly important during the same conditions likely to exacerbate the symptoms of space motion sickness. Using overstimulation of the semicircular canals with a rotary chair as a paradigm for space motion sickness, we evaluated four medications, commonly used for the treatment of terrestrial motion sickness and vertigo, for their efficacy in alleviating the simulated symptoms of space motion sickness. STUDY DESIGN: Randomized, prospective, double-blind study. SETTING: Tertiary referral center. PATIENTS: Healthy male and female volunteers, 18 years of age or older, without history of neurologic or psychiatric disorders, and with no known allergies or any previous adverse reactions to the drugs used. INTERVENTIONS: Lorazepam 1 mg, meclizine 25 mg, promethazine 25 mg, scopolamine 0.4 mg, or placebo. MAIN OUTCOME MEASURE: The ability of each treatment to control the nausea and vomiting associated with our paradigm for space motion sickness was evaluated by measuring time of rotation pre- and posttreatment and time of symptom onset pre-and posttreatment. RESULTS: Only scopolamine effected a mean change in duration of rotation that reached statistical significance when compared with placebo (p <0.008), with a greater than 40% increase in rotation time. Results with promethazine were not statistically significant. CONCLUSION: Results showed a rank order of efficacy of scopolamine > promethazine > placebo > meclizine > lorazepam. Scopolamine significantly increased rotation time, but none of the treatments resulted in a significant delay to onset of symptoms.

Adolescent↗
PubMed1984

Influence of long-term repetitive rotatostimulations on lateral semicircular canals.

Sixty-five guinea pigs were used to investigate the influence of rotatostimulations on the lateral crista ampullaris. After repeated turning stimulations with the cupulometric mode (the terminal turning velocity: 180 degrees/sec) for 24-72 hours, the morphological changes in the crista ampullaris on the ampullopetal flow side were compared with those on the ampullofugal flow side by using scanning and transmission electron microscopy. Postrotatory nystagmus recorded by ENG during this experiment revealed the response decline phenomenon in all animals, and the caloric test performed after the rotatostimulation showed 'canal paresis' in the ear on the ampullopetal flow side. In a group stimulated for 24 hours, no particular damage on the crista ampullaris was noticed. However, in a group stimulated for 72 hours, local damage was dominant in the central part of the crista, which showed a tendency to extend towards the planum semilunatum according to an increment of changes. These findings were more remarkable on the ampullopetal flow side than on the ampullofugal flow side, suggesting the predominant effect of the ampullopetal endolymph flow in the lateral semicircular canal.

Animals↗
PubMed1999

Development of blood-labyrinth barrier in the semicircular canal ampulla of the rat.

Cationic polyethyleneimine (PEI) administered intravenously was transported to anionic sites on the capillary and subepithelial basal laminae (BL) in the vestibular labyrinth. Therefore, changes in the PEI distribution on the BL reflect changes in the transport system in the vestibular labyrinth. A 0.1% PEI solution was administered intravenously (7.5 ml/kg) to developing (1, 4, 7, 14 days after birth) and adult rats in order to investigate the development of the macromolecular transport in the ampulla of the semicircular canal as a function of age. After 1 h, the bony labyrinth was removed and embedded in Epoxy resin. Ultrathin sections of the ampulla were then examined with a transmission electron microscope. In the subepithelial BL in the dark cell area and capillary BL in the crista ampullaris, the PEI distribution in both 1- and 4-day-old rats was markedly increased compared to that in either 7-, 14-day or adult rats. In the sensory cells in 1-, 4-day or 7-day-old rats, PEI density and area was significantly greater than in the adult rats. These findings suggest that the macromolecular transport system in the developing rat ampulla becomes mature by 14 days after birth and that the maturation of its transport system in the ampulla is strongly associated with that in the stria vascularis.

Animals↗
PubMed1984

Simulation of vestibular semicircular canal responses during righting movements of a freely falling cat.

The righting maneuver of a freely falling cat was filmed at 1000 pictures per second, and the head position about the roll axis was digitized from each film frame using a graphics input tablet. The head angular velocity and acceleration were computed from the roll axis position trajectory. Head acceleration trajectories approximated two periods of a damped sinusoid at a frequency of 26 Hz. Head acceleration peak amplitudes exceeded 120,000 deg/s2. These trajectories were used as stimuli for the horizontal semicircular canals in a computer simulation of first-order afferent responses during the fall. Linear system afferent response dynamics, characterized in a previous study of the cat horizontal canal using pseudorandom rotations, provided the basis for linear predictions of falling cat afferent responses. Results showed predicted single afferent firing rates that exceeded physiological values; and variations in afferent sensitivities and phase were predicted among different neurons. Fast head movement information could be carried by ensemble populations of vestibular neurons, and a phase-locking encoding hypothesis is proposed which accomplishes this. Implications for central program versus peripheral vestibular feedback strategies for motor control during falling are presented and discussed.

Afferent Pathways↗
PubMedDate not supplied

[The treatment of benign paroxysmal positional vertigo of the lateral semicircular canal by positional manipulation].

A case of left horizontal-canal benign paroxysmal positional vertigo (HC-BPPV) in a woman with a 7-year history of episodic vertigo when turning over in bed is reported. The diagnosis was established with the patient lying down with her head raised 30 degrees with respect to the horizontal plane. Treatment with positional maneuvers (270 degrees contralateral head rotation in 3 steps) resolved the attacks. Positional testing failed to elicit symptoms 7 days, 14 days, 1 month, and 2 months after treatment. Four months after treatment, the patient remains asymptomatic. Published cases of HC-BPPV are discussed, as well as the differential diagnosis with posterior semicircular canal BPPV.

Adult↗
PubMed2005

[Clinical study on canalith repositioning procedure for benign paroxysmal positional vertigo of semicircular canal].

OBJECTIVE: To determine the effectiveness of canalith repositioning procedure for the treatment of benign paroxysmal positional vertigo (BPPV). METHOD: Medical records from two hundred and thirty cases with benign paroxysmal positional vertigo treated between January 2002 to June 2004 were analyzed retrospectively. Patients were divided into two groups,treatment group (122 cases) and control group (108 cases). Treatment group received a single treatment of canalith repositioning procedure based on the hypothesis that the vertigo and nystagmus of BPPV were due to debris floating in the long arm of the semicircular canal. Treatment outcome was analyzed after two weeks classified as cure, improvement or no change. RESULT: After a single treatment of canalith repositioning procedure, the vertigo and nystagmus in 88 cases of treatment group immediately or gradually disappeared in 1-2 weeks, 18 cases improved, 16 cases got no effect. Complete remission of vertigo and nystagmus was found in 72.1%, the total improvement rate was 86.9%. The vertigo and nystagmus in 51 cases of control group immediately disappeared in 1-2 weeks, 23 cases improved, 34 cases got no effect. Complete remission of vertigo and nystagmus was found in 47.2%, the total improvement rate was 68.5%, and the difference between groups was very significant (P < 0.001, P < 0.01). CONCLUSION: The canalith repositioning procedure was effective for most patients with benign paroxysmal positional vertigo and can be recommended as the first-line treatment modality.

Adult↗
PubMedDate not supplied

Interaction of semicircular canal stimulation with carotid baroreceptor reflex control of heart rate.

The carotid-cardiac baroreflex contributes to the prediction of orthostatic tolerance; experimental attenuation of the reflex response leads to orthostatic hypotension in humans and animals. Anecdotal observations indicate that rotational head movements about the vertical axis of the body can also induce orthostatic bradycardia and hypotension through increased parasympathetic activity. We therefore measured the chronotropic response to carotid baroreceptor stimulation in 12 men during varying conditions of vestibulo-oculomotor stimulation to test the hypothesis that stimulation of the semicircular canals associated with head movements in the yaw plane inhibits cardioacceleration through a vagally mediated baroreflex. Carotid-cardiac baroreflex response was assessed by plotting R-R intervals (ms) at each of 8 neck pressure steps with their respective carotid distending pressures (mmHg). Calculated baroreflex gain (maximal slope of the stimulus-response relationship) was measured under 4 experimental conditions: 1) sinusoidal whole-body yaw rotation of the subject in the dark without visual fixation (combined vestibular-oculomotor stimulation); 2) yaw oscillation of the subject while tracking a small head-fixed light moving with the subject (vestibular stimulation without eye movements); 3) subject stationary while fixating on a small light oscillating in yaw at the same frequency, peak acceleration, and velocity as the chair (eye movements without vestibular stimulation); and 4) subject stationary in the dark (no eye or head motion). Head motion alone and with eye movement reduced baseline baroreflex responsiveness to the same stimulus by 30%. Inhibition of cardioacceleration during rotational head movements may have significant impact on functional performance in aerospace environments, particularly in high-performance aircraft pilots during high angular acceleration in aerial combat maneuvers or in astronauts upon return from spaceflight who already have attenuated baroreflex functions.

Baroreflex↗
PubMedDate not supplied

Influence of otolith organs, semicircular canals, and neck afferents on post-rotatory nystagmus.

The duration of post-rotatory nystagmus is known to be shortened by head tilt, a phenomenon that has been attributed to rapid discharge of the velocity storage mechanism. The relative importance of the various sensory signals associated with post-rotatory head tilt is unknown. Using both earth-vertical axis and off-vertical axis rotation, we investigated this issue in humans by combining sudden termination of constant velocity rotation with several post-rotatory maneuvers that stimulated combinations of otolith organ, somatosensory, and vertical semicircular canal afferents. Results indicated that horizontal post-rotatory nystagmus was shortened by maneuvers that move the head from upright to off-vertical and by cessation of dynamic otolith stimuli. Somatosensory, neck afferent, and transient vestibular stimulation had no consistent effect. We conclude that tilt suppression of postrotatory nystagmus and the short time constant following off-vertical axis rotation is primarily a function of otolith influence on the velocity storage system.

Adult↗
PubMed2005

Morphological aspects of potassium flow in the semicircular canal ampulla of the pigeon.

Potassium ions are a prerequisite for the development and regulation of sensory cell stimulation in the inner ear. From the potassium-rich endolymph the ions flow into the sensory cells apically and are released basolaterally. After transport pathways of various lengths potassium is released again into the endolymph - in the cochlea by marginal cells of the stria vascularis, in the vestibular labyrinth by dark cells. While this long recycling pathway is relatively well-known in the cochlea, few studies have been conducted on the semicircular canal ampullae (SCCA) where its morphological basis is largely unknown. According to the present electron microscopic findings, potassium ions are initially released into the extracellular space during stimulation of the sensory cells and then absorbed by supporting and light cells. Finally they are transported transcellularly over numerous very long gap junctions into the region of the dark cells. From here they move to an extracellular compartment, which is more or less completely sealed off basally by basal plates of the light cells. Apically the intercellular space between light and dark cells is sealed by junctional complexes. This newly identified space in the SCCA corresponds to the extracellular compartment between the marginal and intermediate cells in the stria vascularis. At both sites, the cochlea and the SCCA, this probably serves as a regulatory valve, reservoir or storage space, particularly for potassium ions. It is likely that the different morphology of the ion transport pathways is related to the different flow levels of potassium ions expressed by the different levels of the so-called endocochlear potential and concomitant movement of other ions in the cochlea and SCCA.

Animals↗
PubMed1997

Cochlear changes following destruction of semicircular canal in healthy and previously toxin-exposed rats. An electrophysiological and morphological investigation.

One group of Sprague-Dawley rats (group A, n = 6) was treated by instilling Pseudomonas aeruginosa exotoxin A (PaExoA), and another (group B, n = 6) treated similarly with Haemophilus influenzae type b endotoxin (HiBEndo). In group A a 20 dB hearing loss was observed, predominantly in the high-frequency region, which was reversible within 1 month. In group B no significant hearing impairment was noted. Between 1 and 6 months later, the lateral and posterior semicircular canals (SCCs) were ablated unilaterally. Control rats (group C, n = 8) were subjected to ablation only. All rats were cochleotomized contralaterally prior to labyrinthine surgery. Frequency-specific evoked potential testing at 2-31.5 kHz tone bursts was performed before and directly after surgery, 6, 24 and 48 hours and 1, 4 and 16 weeks postoperatively. After surgery in 18 rats, thresholds rose immediately, predominantly at 2, 4 and 6 kHz, followed by varying degrees of recovery. Greatest immediate postoperative hearing loss was observed in group A; no rat recovered completely and two rats showed severe permanent threshold elevation. All group B rats recovered completely, except one showing moderate threshold impairment. No permanent hearing loss was observed in group C. This study shows that destruction of SCCs in rats does not necessarily cause permanent hearing loss, even if the fluid spaces are not sealed off. However, previous exposure of the middle ear to PaExoA (but not HiBEndo) renders the cochlea more vulnerable and can result in persistent hearing loss.

Animals↗
PubMed2002

Occurrence of semicircular canal involvement in benign paroxysmal positional vertigo.

OBJECTIVES: To study the occurrence of each variant of benign paroxysmal positional vertigo (BPVV) and to present some specific clinical features and the results of their treatment by appropriate repositioning maneuvers. STUDY DESIGN: A retrospective review of the records of patients with BPPV. SETTING: Neurotology clinic of the ear, nose, and throat department of a general hospital. PATIENTS: One hundred twenty-two patients were included in the study, 54 male and 68 female, mean ages 61.8 and 59.6 years, respectively, ranging in age from 25 years to 86 years and with symptoms lasting for an average of 124 days. The diagnosis of each type of BPPV was based on the history of the patients and on the positive results of the appropriate provoking maneuver. METHODS: From all the patients, a comprehensive history was obtained, followed by clinical examination of the ears, nose, and throat and a complete audiologic and neurotologic examination, including electronystagmography. All patients were treated with an appropriate repositioning maneuver, depending on the type of BPPV. RESULTS: Of 122 patients, 110 had posterior canal involvement, 10 had horizontal canal involvement, and only 2 had the anterior canal variant. The canalith repositioning procedure was immediately successful in 106 patients and in 8 more patients proved successful after its repetition in a second session, resulting in a total success rate of 93.4%. CONCLUSIONS: All the BPPV variants shared the same clinical and demographic characteristics and responded equally well to treatment. However, differential diagnosis was necessary to apply the appropriate canalith repositioning procedure. Although data from clinical and histologic studies do not fully account for the observed relative occurrence of each variant of BPPV, a satisfactory explanation may be provided by the anatomic location of each semicircular canal and additionally by self-treatment of most cases of the horizontal and the anterior canal variety.

Adult↗
PubMed1996

Skew deviation of the eyes in normal human subjects induced by semicircular canal stimulation.

Computerised video-oculography and scleral search coils were used to record the horizontal, vertical and torsional binocular eye movements of human subjects exposed to roll oscillation at 0.4 Hz about earth-horizontal and earth-vertical naso-occipital axes in darkness. The stimuli provoked a dominant torsional ('ocular counter-rolling') response with a ratio of peak slow phase eye velocity to stimulus velocity which was not significantly different for earth-horizontal (0.39, SD 0.08) or earth-vertical axis orientations (0.40, SD 0.08). For all conditions the responses also had a head-vertical component which was disconjugate ('skew deviation'). The cumulative, vertical, slow phase divergence was 5.8 degrees, SD 1.3 degrees, about upright and 4.3 degrees, SD 0.6 degrees, when supine. This is the first demonstration that dynamic roll stimuli provoke a skew deviation in normal human subjects. At the frequency tested, the skew was driven by vertical semicircular canal stimulation.

Adult↗
PubMed2005

On the role of otoliths and semicircular canals in spatial orientation: Dynamics of the visually perceived eye level during gondola centrifugation.

The visually perceived eye level (VPEL) was measured during gondola centrifugation. Subjects (N = 11) were seated upright, facing motion in a swing-out gondola The head was adjusted so that Reid's baseline was tilted 10 degrees anterior end up. The subjects were requested to adjust the position of a small luminous dot so that it was perceived as gravitationally at eye level. In the 1-g environment, the VPEL was a few degrees below the true gravitational eye level (M = -1.75 degrees, SD = 1.90 degrees). After rapid acceleration of the centrifuge to 2 G (vectorial sum of the earth gravity force and the centrifugal force), there was an exponentially increasing depression of the VPEL. The initial value was -6.4 degrees +/- 5.2 degrees. During 10 min at 2 G, the VPEL approached an asymptotic value of -24.8 degrees +/- 5.4 degrees. The time constant showed a large interindividual variability, ranging from 59 to 1,000 sec (M = 261 sec, median = 147 sec). The findings are discussed, taking into consideration otolith-semicircular-canal interaction, as well as memory functions of the vestibular system.

Adult↗