Journal of Vestibular Research - Volume 9, issue 4

Authors: Allum, John H.J. | Shepard, Neil T.

Article Type: Research Article

Abstract: Dynamic posturography comprises a series of balance control tests which help physicians overcome numerous diagnostic and treatment challenges arising when examining patients complaining of a debilitating balance disorder. These challenges include the specific differential diagnosis, documentation of symptoms and assessment of functional disability. It must be determined whether the cause of the disability is an organic sensory deficit, a central nervous system (CNS) lesion or a non-organic (that is, possibly psychogenic or just overtly simulated) disorder. This review is targeted towards providing the reader (a) an overview of the effects sensori-motor deficits have on balance control, specifically vestibulo-spinal and proprioceptive …reflex deficits; and, (b) how these effects may be assessed objectively in a clinical setting to differentiate between various organic and non-organic balance-disorders. The techniques used to study these effects are based on the analysis of both rapid balance-correcting and slow balance-stabilizing responses to fast and slow movements in the pitch plane of the support surface on which the test subject stands. Show more

Keywords: human postural control, human balance control, peripheral vestibular deficit, lower-leg proprioceptive loss, balance disorders, EMG activity, motion analysis

DOI: 10.3233/VES-1999-9401

Citation: Journal of Vestibular Research, vol. 9, no. 4, pp. 223-252, 1999

Authors: Whitney, S.L. | Hudak, M.T. | Marchetti, G.F.

Article Type: Research Article

Abstract: Vestibular dysfunction can have a tremendous impact on an individual’s quality of life. The purpose of this paper is to determine if the level of handicap reported by individuals on the Dizziness Handicap Inventory (DHI), an inventory developed for use with individuals with complaints of dizziness symptoms, will be consistent with that reported on the Activities-specific Balance Confidence Scale (ABC), a tool developed for use with elderly individuals that attempts to assess a person’s confidence level in performing activities of daily living (ADL’s). A sample of convenience was used consisting of 71 subjects (15 males and 56 females) from a …local Balance and Vestibular Clinic. The subjects ranged in age from 26 to 88 years of age. Both the DHI and the ABC were administered as part of an initial physical therapy evaluation to new patients at the clinic. A moderately strong negative correlation was found between the scores of the two inventories (r s = − 0.6350 ). The results suggest that the ABC is a valid tool for use with individuals with complaints of dizziness. Show more

Keywords: dizziness, falls, fear, daily living activities

DOI: 10.3233/VES-1999-9402

Citation: Journal of Vestibular Research, vol. 9, no. 4, pp. 253-259, 1999

Authors: Matheson, Anna J. | Darlington, Cynthia L. | Smith, Paul F.

Article Type: Research Article

Abstract: Vestibular dysfunction can have a tremendous impact on an individual’s quality of life. The purpose of this paper is to determine if the level of handicap reported by individuals on the Dizziness Handicap Inventory (DHI), an inventory developed for use with individuals with complaints of dizziness symptoms, will be consistent with that reported on the Activities-specific Balance Confidence Scale (ABC), a tool developed for use with elderly individuals that attempts to assess a person’s confidence level in performing activities of daily living (ADL’s). A sample of convenience was used consisting of 71 subjects (15 males and 56 females) from a …local Balance and Vestibular Clinic. The subjects ranged in age from 26 to 88 years of age. Both the DHI and the ABC were administered as part of an initial physical therapy evaluation to new patients at the clinic. A moderately strong negative correlation was found between the scores of the two inventories (r s = − 0.6350 ). The results suggest that the ABC is a valid tool for use with individuals with complaints of dizziness. Show more

Keywords: aging, vestibular system, posture

DOI: 10.3233/VES-1999-9403

Citation: Journal of Vestibular Research, vol. 9, no. 4, pp. 261-264, 1999

Authors: Borello-France, Diane F. | Gallagher, Jere D. | Redfern, Mark | Furman, Joseph M. | Carvell, George E.

Article Type: Research Article

Abstract: This study compared voluntary movement strategies of patients with unilateral peripheral vestibular hypofunction with those of age-matched healthy control subjects. All subjects performed three voluntary movement tasks with their dominant upper extremity: a forward flexion arm movement through 90 degrees, a reach to an overhead target, and a reach to a side target. Subjects performed the movement tasks sitting and standing (Body Position), and under precued and choice reaction time (RT) conditions (Task Certainty). Measures of motor planning and movement execution included RT and movement time (MT), respectively. Statistical analysis included separate Group x Task Certainty x Body Position ANOVA …calculations for each task. Across tasks, results suggested no between group differences for RT. A Task Certainty main effect for the side and overhead tasks indicated that the choice RT situation resulted in longer RTs as compared to the precued RT condition. Movement time differed between the two groups. Across all three voluntary movement tasks, vestibular impaired subjects moved more slowly than control subjects. Providing vestibular subjects with a precue did not bring MT performance to the level of controls. Body position influenced MT for the side task only. Across both groups of subjects, MT for the side task was longer when performed in the standing position. The results of this study suggest that individuals with unilateral peripheral vestibular hypofunction initiate voluntary movement responses with similar timing as control subjects, but require more time to complete the movement. Vestibular rehabilitation should include goal-directed movement and should address issues of movement speed. Show more

Keywords: unilateral peripheral vestibular hypofunction, voluntary movement control, reaction time, movement time

DOI: 10.3233/VES-1999-9404

Citation: Journal of Vestibular Research, vol. 9, no. 4, pp. 265-275, 1999

Authors: Carpenter, Mark G. | Frank, James S. | Silcher, Cathy P.

Article Type: Research Article

Abstract: One possible factor influencing the control of upright stance is the perceived threat to one's personal safety, i.e. balance confidence. We explored this factor by examining the control of stationary stance when standing on an elevated platform under various conditions of reduced visual and vestibular inputs. Twenty-eight adults (14 male and 14 female, mean age = 23.5 years) participated in the experiment. Postural control was examined by recording the amplitude variability (RMS) and mean power frequency (MPF) of center of pressure excursions (COP) over a 2-minute interval while participants stood in a normal stance on a low (0.19 m) and …a high (0.81 m) platform with toes positioned either at or away from the edge of the platform. Vision was manipulated through eyes open and eyes closed trials. Vestibular input was reduced by tilting the head into extension [1]. Anterior-posterior RMS and MPF of COP were significantly influenced by an interaction between surface height and vision. When vision was available, a significant decrease in RMS was observed during quiet standing on a high surface compared to a low surface independent of step restriction. When vision was available MPF increased when subjects were raised from a low to a high surface. The mean position of the COP was significantly influenced by an interaction between height and step restriction. Differences in RMS and MPF responses to height manipulation were observed between genders in eyes closed conditions. Vestibular input influenced postural control at both low and high levels with significant increases in RMS when vestibular input was reduced. The reciprocal changes observed in RMS and MPF suggest modifications to postural control through changes in ankle stiffness. Vision appears to play a role in increasing ankle stiffness when balance confidence is compromised. Show more

Keywords: fear of falling, centre of pressure, vision, vestibular, height, postural control

DOI: 10.3233/VES-1999-9405

Citation: Journal of Vestibular Research, vol. 9, no. 4, pp. 277-286, 1999

Authors: Fushiki, Hiroaki | Takata, Satoru | Nagaki, Yasunori | Watanabe, Yukio

Article Type: Research Article

Abstract: We have used optokinetic stimulation in patients with unilateral age-related macular degeneration (AMD) and central scotoma to investigate the possible contribution of the central visual field to circular vection (CV). Six patients aged 42–73 years with unilateral AMD and an aged-matched control group of nine elderly adults aged 47–75 years were examined. Monocular visual field defects were verified with the Goldmann perimeter by kinetic perimetry. The device used to induce CV was a random dot pattern projected onto a hemispherical dome with a radius of 75 cm. The pattern was rotated horizontally at a constant acceleration of 1 deg/s 2 …. Monocular stimuli were randomly repeated two to three times in both temporal-nasal (T-N) and nasal-temporal (N-T) directions. The latency of onset of CV was measured for each stimulus presentation. In the age-matched control group the CV latencies varied from 4.2 to 72.0 s. In each case, however, the CV latencies were stable. No significant differences in CV latencies were found between right and left eyes in both stimulus directions (p > 0.05 ). In patients with AMD, no statistically significant difference in CV latency was found between the affected and unaffected eyes (p > 0.05 ). Marked central visual field loss in AMD does not significantly impair peripherally induced CV. Our results are compatible with the hypothesis that the peripheral retina dominates CV. Show more

Keywords: self-motion, central vision loss, peripheral retina, optokinetic

DOI: 10.3233/VES-1999-9406

Citation: Journal of Vestibular Research, vol. 9, no. 4, pp. 287-291, 1999

Authors: Dai, Mingjia | Klein, Avniel | Cohen, Bernard | Raphan, Theodore

Article Type: Research Article

Abstract: The time constant of the angular vestibulo-ocular reflex (aVOR), measured from the response to steps of rotation about a yaw axis, has frequently been estimated as a single exponential. However, the slow phase velocity envelope during per- or post-rotatory nystagmus is more accurately represented by two exponential modes. One represents activity in the vestibular nerve induced by deflection of the cupula, the other by activation that the input from the canals produces in the central velocity storage integrator. The sum of the cupula and the integrator responses describes the overall response of slow phase eye velocity and can be approximated …by a double exponential. Frequently, there is a plateau in the initial portion of eye velocity response, but this may be masked by habituation, making the cupula contribution unobservable and impossible to estimate. Using a model-based technique to analyze responses with a clear plateau, we estimated peripheral and central vestibular time constants by double exponential fits to slow phase eye velocity. Cupular time constants were varied from 1 to 10 s to identify values that gave optimal fits of the data according to a Chi-square criterion. The mean cupular time constant for 10 human subjects was 4.2 ± 0.6 s. Fits of the data were also good for time constants between 3.5 to 7 s, but not for 1 to 3 or 7.5 to 10 s. The estimated cupular time constants also fit responses where there was no plateau. In 8 monkeys, cupular time constants were estimated as 3.9 ± 0.5 s, which agreed with those derived from activity in the vestibular nerve. There was no difference between monkey and human cupular time constants from these estimates. It is likely that the human cupular time constant is similar to that of the monkey and shorter than previously thought. Show more

Keywords: vestibulo-ocular reflex (VOR), cupula, velocity storage, yaw axis time constant, human, monkey

DOI: 10.3233/VES-1999-9407

Citation: Journal of Vestibular Research, vol. 9, no. 4, pp. 293-301, 1999