Journal of Vestibular Research - Volume 11, issue 6

Authors: Kolev, Ognyan I.

Article Type: Research Article

Abstract: Purpose: To further investigate the direction of (I) nystagmus and (II) self-motion perception induced by two stimuli: (a) caloric vestibular stimulations and (b) a sudden halt during vertical axis rotation. Subjects and methods: Twelve normal humans received caloric stimulation at 44°C, 30°C, and 20°C while in a supine position with the head inclined 30° upwards. In a second test they were rotated around the vertical axis with the head randomly placed in two positions: tilted 30° forward or tilted 60° backward, at a constant velocity of 90°/sec for 2 minutes and then suddenly stopped. After both tests …they were asked to describe their sensations of self-motion. Eye movements were recorded with an infrared video-technique. Results: Caloric stimulation evoked only horizontal nystagmus in all subjects and induced a non-uniform complex perception of angular in frontal and transverse planes (the former dominated) and linear movements along the antero-posterior axis (sinking dominated) of the subject's coordinates. The self-motion was felt with the whole body or with a part of the body. Generally the perception evoked by cold (30°C) and warm (44°C) calorics was similar, although there were some differences. The stronger stimulus (20°C) evoked not only quantitative but also qualitative differences in perception. The abrupt halt of rotation induced self-motion perception and nystagmus only in the plane of rotation. The self-motion was felt with the whole body. Conclusion: There was no difference in the nystagmus evoked by caloric stimulation and a sudden halt of vertical axis rotation (in head positions to stimulate the horizontal canals); however, the two stimuli evoked different perceptions of self-motion. Calorics provoked the sensation of self-rotation in the frontal plane and linear motion, which did not correspond to the direction of nystagmus, as well as arcing and a reset phenomenon during angular and linear self-motion, caloric-induced self-motion can be felt predominantly or only with a part of the body, depending on the self-motion intensity. The findings indicate that, unlike the self-motion induced by sudden halt of vertical axis rotation, several mechanisms take part in generating caloric-induced self-motion. Show more

Keywords: caloric test, vertical axis rotation, eye movement, self-motion perception, vestibular stimulation

DOI: 10.3233/VES-2002-11601

Citation: Journal of Vestibular Research, vol. 11, no. 6, pp. 349-355, 2002

Authors: Tang, Yong | Lopez, Ivan | Baloh, Robert W.

Article Type: Research Article

Abstract: An unbiased stereological method was used to assess the effect of aging on the number of neurons in the human medial vestibular nucleus. We studied 13 normal brainstem specimens (age at death from 40 to 93 years) that were part of a prior study that counted neuronal profiles and used a correction factor to estimate the number of neurons in the human vestibular nucleus. On average, we found 151 · 10 3 (CV = 0.15 ) neurons in the medial vestibular nucleus, which is 18% significant decrease in the number of neurons …with aging. This age-related neuronal loss in the vestibular nucleus could have important functional implications regarding the well-known deterioration in balance that occurs with aging. Show more

Keywords: human medial vestibular nucleus, neuron, number, aging, stereology, fractionator

DOI: 10.3233/VES-2002-11602

Citation: Journal of Vestibular Research, vol. 11, no. 6, pp. 357-363, 2002

Authors: Furman, Joseph M. | Redfern, Mark S.

Article Type: Research Article

Abstract: This study assessed visual-otolith interaction in healthy older humans and compared responses from older subjects to those of younger subjects. Using off-vertical axis rotation (OVAR) to stimulate the otolith organs, eye movement responses, measured using electro-oculography, were recorded during rotation in the dark, rotation with an earth-fixed lighted visual surround, and rotation with a subject-fixed fixation target. Results indicated that older subjects, like young subjects, exhibit a modulation component that was as large during rotation with a lighted earth-fixed visual surround as that seen in the dark and a modulation component during rotation with a subject-fixed visual target that was …incompletely suppressed. The modulation component was, in general, larger in the older subjects. This study confirms findings from a previous study of visual-otolith interaction in young subjects and suggests that older subjects, like young subjects, have difficulty visually suppressing the modulation component induced by off-vertical axis rotation. Show more

Keywords: vestibulo-ocular reflex, otolith, human, aging

DOI: 10.3233/VES-2002-11603

Citation: Journal of Vestibular Research, vol. 11, no. 6, pp. 365-370, 2002

Authors: Buchanan, John J. | Horak, Fay B.

Article Type: Research Article

Abstract: Twelve subjects, 6 bilateral vestibular-loss (3 well compensated and 3 poorly compensated) and 6 controls, attempted to maintain balance during anterior-posterior sinusoidal surface translation at 6 different frequencies. For frequencies ≤ 0.25 Hz well compensated and control subjects rode the platform by fixing the head and upper-trunk with respect to the support surface, and for frequencies ≥ 0.75 Hz, these subjects fixed their head/upper-trunk in space. Poorly compensated vestibular subjects showed large head and center of mass variability and were unable to balance at frequencies requiring a head fixed in space pattern. All vestibular subjects were less stable with vision …than the controls. Without vision, vestibular subjects experienced more falls than the controls at all frequencies, with falls observed in 61% trials and 16% information is important in stabilizing head and upper-trunk motion in space. Visual and somatosensory information can compensate, in part, for vestibular-loss. The results are discussed in light of models that characterize postural control in a vestibular/visual top-down and somatosensory bottom-up manner. Show more

DOI: 10.3233/VES-2002-11604

Citation: Journal of Vestibular Research, vol. 11, no. 6, pp. 371-389, 2002

Authors: Dimitri, P.S. | Wall III, C. | Rauch, S.D.

Article Type: Research Article

Abstract: Although patient symptoms and an audiogram can typically identify the affected ear or ears in Ménière's disease, there are some cases where this differentiation is problematic. This paper concentrates on the sole use of vestibular test data to discriminate between unilateral and bilateral Ménière's disease. Patients that were known to have peripheral unilateral vestibular hypofunction (n = 104) were used as learning groups to define a region in multidimensional measurement space consisting of four vestibular test scores which summarized data from electronystagmography, sinusoidal harmonic acceleration, and computerized dynamic posturography tests. A multivariate boundary was created from the unilateral learning group …that determined thresholds for identifying bilateral vestibular hypofunction. Patients with bilateral Ménière's disease (n = 23) and with bilateral ototoxicity (n = 19) were then used as test subjects to determine the sensitivity of the multivariate boundary. Results showed up to a increase in estimated test sensitivity (specificity = 95%) bilateral vestibular hypofunction. Show more

Keywords: vestibular testing, decision analysis, Ménière's disease, ototoxicity, unilateral vestibular hypofunction, bilateral vestibular hypofunction

DOI: 10.3233/VES-2002-11605

Citation: Journal of Vestibular Research, vol. 11, no. 6, pp. 391-404, 2002

Authors: Dimitri, P.S. | Wall III, C. | Rauch, S.D.

Article Type: Research Article

Abstract: This paper discusses the use of vestibular testing to discriminate between right (n = 29) and left (n = 27) Ménière's disease. We examined reduced vestibular response (RVR), directional preponderance, and spontaneous and positional nystagmus measurements from electronystagmography, as well as the asymmetry measurements from the sinusoidal harmonic acceleration test, to determine whether multivariate logistic regression could improve upon the discrimination performance of RVR alone. We found that patients with a spontaneous or positional nystagmus often had a “recovery nystagmus”, beating in the opposite direction of that predicted for an acute lesion. When present, the direction and magnitude of such …nystagmus could be used in the classification algorithm to increase the discriminatory power over RVR alone, but in these patients the rotation test asymmetry measurements were rendered useless. In the absence of spontaneous or positional nystagmus, asymmetry measurements significantly enhanced right/left discrimination. Directional preponderance was insignificant in determining the side of lesion. Show more

Keywords: vestibular testing, Ménière's disease, decision analysis, unilateral vestibular hypofunction

DOI: 10.3233/VES-2002-11606

Citation: Journal of Vestibular Research, vol. 11, no. 6, pp. 405-412, 2002