Journal of Vestibular Research - Volume 18, issue 2-3

Authors: Kondrachuk, A.V. | Sirenko, S.P. | Boyle, R.

Article Type: Research Article

Abstract: The effect of different densities of a cupula and endolymph on the dynamics of the semicircular canals is considered within the framework of a simplified one-dimensional mathematical model where the canal is approximated by a torus. If the densities are equal, the model is represented by Steinhausen's phenomenological equation. The difference of densities results in the complex dynamics of the cupulo-endolymphatic system, and leads to a dependence on the orientation of both the gravity vector relative to the canal plane and the axis of rotation, as well as on the distance between the axis of rotation and the center of …the semicircular canal. Our analysis focused on two cases of canal stimulation: rotation with a constant velocity and a time-dependent (harmonically oscillating) angular velocity. Two types of spatial orientation of the axis of rotation, the axis of canal symmetry, and the vector of gravity were considered: i) the gravity vector and axis of rotation lie in the canal plane, and ii) the axis of rotation and gravity vector are normal to the canal plane. The difference of the cupula and endolymph densities reveals new features of cupula dynamics, for instance – a shift of the cupula to a new position of equilibrium that depends on the gravity vector and the parameters of head rotation, and the onset of cupula oscillations with multiple frequencies that results in the distortion of cupula dynamics relative to harmonic stimulation. Factors that might influence the density difference effects and the conditions under which these effects occur are discussed. Show more

Keywords: Semicircular canal, cupula, endolymph, modeling

DOI: 10.3233/VES-2008-182-301

Citation: Journal of Vestibular Research, vol. 18, no. 2-3, pp. 69-88, 2008

Authors: Valli, Paolo | Botta, Laura | Zucca, Gianpiero | Valli, Stefano | Buizza, Angelo

Article Type: Research Article

Abstract: The physical mechanisms responsible for cupulolithiasis and canalolithiasis have been investigated by two groups of experiments in isolated posterior semicircular canal (SCC) of frog (Rana esculenta L.). First, clouds of 10-30 isolated otoconia were let to fall (snowfall of otoconia) either through the ampulla onto the cupula, or inside the long arm of the canal, opposite to the cupula. Second, microspheres ranging 30 to 350 μm in diameter were gently moved to and fro inside the long arm of the canal by a micromanipulator. The effects were evaluated by recording the firing rate (Nfr) of the ampullary nerve. Snowfall of …otoconia produced detectable changes of Nfr only when otoconia got in contact with the cupula, but not when falling through the endolymph. Movement of the microspheres in the canal long arm induced Nfr changes only if the microsphere diameter exceeded about 50 μm. Although the exact microsphere size needed for receptor stimulation may depend on the experimental conditions, these results strongly suggest that debris moving inside a SCC (canalolithiasis) can produce transcupular pressures able to stimulate ampullar receptors only if they have suitable size, whereas isolated otoconia cannot, except when lying on the cupula (cupulolithiasis). Show more

Keywords: Benign Paroxysmal Positional Vertigo (BPPV), canalolithiasis, cupulolithiasis, frog, isolated semicircular canal, otoconia

DOI: 10.3233/VES-2008-182-302

Citation: Journal of Vestibular Research, vol. 18, no. 2-3, pp. 89-96, 2008

Authors: Nooij, Suzanne A.E. | Bos, Jelte E. | Groen, Eric L.

Article Type: Research Article

Abstract: Adaptation to a novel gravitational state involves adaptation of vestibular mediated responses, in particular those mediated by the otolith organs. The present paper investigates whether the orientation of Listing's plane, which is under control of otolith signals, is affected by sustained exposure to hypergravity. Subjects were exposed to four G-loads differing in duration (45 or 90 min) and magnitude (2 or 3G). During centrifugation subjects were in a supine position, directing the gravito-inertial acceleration along the naso-occipetal axis. We determined the orientation of Listing's plane before and after each centrifuge run, with the head erect and tilted in pitch. Head …tilt in pitch induced a counter-pitch of Listing's plane, which was found to be less pronounced after centrifugation. In addition, exposure to 3G for 90~min induced a small backward tilt of Listing's plane compared to the pretest orientation (head erect). In order to explain these results a hypothesis is discussed, proposing that the orientation of Listing's plane in the head is governed by a head fixed orientation vector that is modulated by the direction of gravity relative to the head. Sustained centrifugation is proposed to decrease this gravitational modulation, leading to the effects observed. This could reflect a shift towards a more body centered frame of reference. Show more

Keywords: Three-dimensional eye movements, listing's plane, hypergravity, vestibular adaptation, head pitch

DOI: 10.3233/VES-2008-182-303

Citation: Journal of Vestibular Research, vol. 18, no. 2-3, pp. 97-105, 2008

Authors: Konishi, Taku | Suetsugu, Akira | Matsushima, Takaji

Article Type: Research Article

Abstract: We measured the change in subjective straight-ahead (SSA) as a function of time after vestibular stimulation. Blindfolded subjects were exposed to sudden stops after constant velocity (72°/s) z-axis rotation. They were then asked to open their eyes and continuously adjust the position of a laser spot to the position perceived as straight ahead (visual localization of SSA) immediately, or after a 10 s or 20 s delay following the sudden stop. The deviation of SSA increased to 20 s in the opposite direction of acceleration and then decreased gradually when the visual localization task was started immediately after sudden stops. …The time courses changed systematically when the task was started after a delay of 10 s or 20 s following sudden stops: the initial increase component and maximum magnitude of the SSA deviation fell off with delay length, but the increase-decrease pattern was preserved. These delay effects on the time course of the SSA deviation might reflect that the velocity-to-orientation/position integrator for perception of body orientation in vestibular system might be inactivated temporarily during the delay period after vestibular stimulation without visual input. Show more

Keywords: Vestibular system, subjective straight-ahead, time course, visual and vestibular integration

DOI: 10.3233/VES-2008-182-304

Citation: Journal of Vestibular Research, vol. 18, no. 2-3, pp. 107-116, 2008

Authors: Jombik, Peter | Bahyl, Vladimir | Drobny, Michal | Spodniak, Pavel

Article Type: Research Article

Abstract: Recently several studies have yielded evidence that impulses of bone-conducted (BC) sound can produce short-latency myogenic responses in the extraocular muscles, which are probably mediated by otolithic afferents. These responses, although miniscule, can be recorded with surface electrodes and are termed ocular vestibular evoked myogenic potentials (oVEMP). It is assumed that in response to low-frequency BC-sound stimuli the head moves predominantly along the axis from the site of the applied stimulus to the opposite side. Thus, oppositely-directed accelerations along a particular axis would produce oppositely-directed compensatory vestibulo-ocular responses (VOR) and oVEMPs. The aim of this study was to investigate whether …the oVEMPs would reflect these direction-dependent VOR responses. Single cycles of 125 and 250 Hz BC tones were applied to opposite sides of two approximately orthogonal, naso-occipital (x) and vertical (z) axes of the head. oVEMP responses were recorded with standard bilateral vertical EOG montages. The responses in all twelve healthy subjects showed consistent differences with regard to the latency and/or shape of the response to stimuli applied to opposite sides of the head. These differences likely reflect different patterns of electro-myographic activity of the extraocular muscles, which may be mediated by groups of vestibular (probably otolithic) afferents with differently-orientated spatial polarization vectors. Show more

Keywords: Vestibulo-ocular reflex (VOR), ocular vestibular-evoked myogenic potentials (oVEMP), bone-conducted (BC) sound

DOI: 10.3233/VES-2008-182-305

Citation: Journal of Vestibular Research, vol. 18, no. 2-3, pp. 117-128, 2008

Authors: Jáuregui-Renaud, Kathrine | Ramos-Toledo, Verónica | Aguilar-Bolaños, Miriam | Montaño-Velázquez, Bertha | Pliego-Maldonado, Alejandro

Article Type: Research Article

Abstract: To compare the frequency of symptoms of detachment from the self or from the environment (DD) in patients with an acquired deficiency of the special senses, a questionnaire for DD symptoms [12] and the GHQ12 questionnaire for common mental disorders [16] were auto-administered to patients with hearing-loss (N = 40), peripheral vestibular disease (N = 40) or bilateral retinal disease (N = 40), and to 80 healthy subjects. Patients with retinal disease and patients with vestibular disease reported DD symptoms more frequently & severe than patients with hearing loss and healthy subjects. DD scores were related to the GHQ12 scores …and to the type of sensory dysfunction. DD symptoms are more frequent & severe in patients with an acquired deficiency of the special senses, associated to symptoms of common mental disorders. Show more

Keywords: Derealisation, vestibular, vision, hearing

DOI: 10.3233/VES-2008-182-306

Citation: Journal of Vestibular Research, vol. 18, no. 2-3, pp. 129-137, 2008

Authors: Gabilan, Yeda P.L. | Perracini, Mônica R. | Munhoz, Mario S.L. | Gananç, Fernando F.

Article Type: Research Article

Abstract: Purpose: To explore the effects of aquatic physiotherapy on individuals with unilateral vestibular hypofunction and examine the association of therapeutic effects with age, time since symptom onset and use of antivertigo medication. Study design: Exploratory study. Setting: Tertiary referral center. Patients: Twenty-one patients presenting chronic dizziness with uncompensated unilateral vestibular loss. Intervention: All patients underwent a regimen of 10 sessions of aquatic physiotherapy for vestibular rehabilitation. Main outcome measures: Patient evaluation prior to and following rehabilitation involved the application of the Brazilian version of the Dizziness Handicap Inventory …(DHI), dynamic computerized posturography and the self-perception scale of dizziness intensity. Statistical analysis compared average variables prior to and following rehabilitation using the Student t test. Results: Brazilian DHI total scores were lower following rehabilitation (p = 0.001). Posturography revealed a reduction in the variation of body displacement following rehabilitation in the average stability and anterior/posterior stability indexes (p = 0.001) and in the average medial/lateral stability index (p = 0.003). Self-perception of dizziness intensity was lower following rehabilitation (p = 0.001). No association between age, time since symptom onset and use of antivertigo medication and rehabilitation therapeutic effects were found. Conclusion: Unilateral vestibular hypofunction patients undergoing aquatic physiotherapy for vestibular rehabilitation achieved an improvement in quality of life, body balance and self-perception of dizziness intensity, regardless of age, time since symptom onset, and use of antivertigo medication. Show more

Keywords: Vestibular hypofunction, dizziness, rehabilitation, vestibular adaptation, balance

DOI: 10.3233/VES-2008-182-307

Citation: Journal of Vestibular Research, vol. 18, no. 2-3, pp. 139-146, 2008

Authors: Scherer, Matthew | Migliaccio, Americo A. | Schubert, Michael C.

Article Type: Research Article

Abstract: While active dynamic visual acuity (DVA) has been shown to improve with gaze stabilization exercises, we sought to determine whether DVA during {passive} head impulses (pDVA) would also improve following a rehabilitation course of vestibular physical therapy (VPT) in patients with unilateral and bilateral vestibular hypofunction. VPT consisted of gaze and gait stabilization exercises done as a home exercise program. Scleral search coil was used to characterize the angular vestibulo-ocular reflex (aVOR) during pDVA before and after VPT. Mean duration of VPT was 66 ± 24 days, over a total of 5 ± 1.4 outpatient visits. Two of three subjects …showed improvements in pDVA with a mean reduction of 43% (LogMAR 0.58 to 0.398 and 0.92 to 0.40). Our data suggest improvements in pDVA may be due in part to improvements in aVOR velocity and acceleration gains or reduced latency of the aVOR. Each subject demonstrated a reduction in the ratio of compensatory saccades to head impulses after VPT. Preliminary data suggest that active gaze stability exercises may contribute to improvements in pDVA in some individuals. Show more

Keywords: Vestibular rehabilitation, vestibulo-ocular reflex, dynamic visual acuity, compensatory saccades

DOI: 10.3233/VES-2008-182-308

Citation: Journal of Vestibular Research, vol. 18, no. 2-3, pp. 147-157, 2008

Authors: Yanik, Burcu | Külcü, Duygu Geler | Kurtais, Yesim | Boynukalin, Serife | Kurtarah, Hanifi | Gökmen, Derya

Article Type: Research Article

Abstract: The aim of this study was to adapt the Vertigo Symptom Scale (VSS) and the Vertigo Dizziness Imbalance (VDI) Questionnaires to the Turkish population and investigate the reliability and validity of the Turkish version. One hundred and three patients with Benign Paroxysmal Positional Vertigo (BPPV) were included in the study. The patients were evaluated with the VSS and the VDI twice, at recruitment and 24 hours later. To perform concurrent validity study study, patients were also assessed by the Beck Depression Inventory (BDI) and the Medical Outcomes Survey Short Form 36 (SF-36) which were formerly proved to be valid and …reliable for use in Turkish population. The internal consistency of the VSS, VDI-symptom scale, and VDI-health-related quality of life scale were good with Cronbach's alpha of 0.91, 0.85, and 0.93 respectively which showed high reliability for the Turkish versions. Test-retest reliability was also good, with a high intraclass correlation coefficent (ICC) between the two time points; being 0.83 for the VSS, 0.90 for the VDI-symptom scale and 0.89 for the VDI-health related quality of life scale. Regarding concurrent validity, significant expected correlations were detected between the VSS and BDI (r = 0.55 p < 0.001) and the VSS and SF-36 (r = −0.43 p < 0.001). Significant low correlations were detected between the VDI-SS and BDI (r = 0.20 p < 0.05) and the VDI-SS and SF-36 (r = −0.21 p < 0.05). High correlations were observed between the VDI-HRQoL and BDI (r = −0.75 p < 0.001) and the VDI-HRQoL and SF-36 (r = 0.82, p < 0.001) which indicates high concurrent validity. The correlation between VDI-SS subscale scores and VDI-HRQoL subscale scores were 0.028 (P = 0.778) at the first time point. From the perspective of discriminant validity, it means that the VDI-SS measures a construct different from the one underlying the VDI-HRQoL. The adaptation of the VSS and VDI to the Turkish population was successful and both scales were found to be valid and reliable. Thus, they can be used in Turkish people with BPPV for assessment and monitoring the treatments. Besides, the results of the national studies in which these Turkish versions are used can be compared with those of the international studies. Show more

Keywords: Vertigo, reliability, validity

DOI: 10.3233/VES-2008-182-309

Citation: Journal of Vestibular Research, vol. 18, no. 2-3, pp. 159-170, 2008