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The effect of fear of falling on vestibular feedback control of balance.

ABSTRACT: Vestibular sensation contributes to cervical-head stabilization and fall prevention. To what extent fear of falling influences the associated vestibular feedback processes is currently undetermined. We used galanic vestibular stimulation (GVS) to induce vestibular reflexes while participants stood at ground level and on a narrow walkway at 3.85 m height to induce fear of falling. Fear was confirmed by questionnaires and elevated skin conductance. Full-body kinematics was measured to differentiate the whole-body centre of mass response (CoM) into component parts (cervical, axial trunk, appendicular short latency, and medium latency). We studied the effect of fear of falling on each component to discern their underlying mechanisms. Statistical parametric mapping analysis provided sensitive discrimination of early GVS and height effects. Kinematic analysis revealed responses at 1 mA stimulation previously believed marginal through EMG and force plate analysis. The GVS response comprised a rapid, anode-directed cervical-head acceleration, a short-latency cathode-directed acceleration (cathodal buckling) of lower extremities and pelvis, an anode-directed upper thorax acceleration, and subsequently a medium-latency anode-directed acceleration of all body parts. At height, head and upper thorax early acceleration were unaltered, however, short-latency lower extremity acceleration was increased. The effect of height on balance was a decreased duration and increased rate of change in the CoM acceleration pattern. These results demonstrate that fear modifies vestibular control of balance, whereas cervical-head stabilization is governed by different mechanisms unaffected by fear of falling. The mechanical pattern of cathodal buckling and its modulation by fear of falling both support the hypothesis that short-latency responses contribute to regulate balance.

SUBMITTER: de Melker Worms JLA

PROVIDER: S-EPMC5617925 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The vestibular system is involved in gaze stabilization and standing balance control. However, it is unclear whether vestibular dysfunction affects both processes to a similar extent. Therefore, the objective of this study was to determine how the reliance on vestibular information during standing balance control is related to gaze stabilization deficits in patients with vestibular dysfunction. Eleven patients with vestibular dysfunction and twelve healthy subjects were included. Gaze stabilization deficits were established by spontaneous nystagmus examination, caloric test, rotational chair test, and head impulse test. Standing balance control was assessed by measuring the body sway (BS) responses to continuous support surface rotations of 0.5° and 1.0° peak-to-peak while subjects had their eyes closed. A balance control model was fitted on the measured BS responses to estimate balance control parameters, including the vestibular weight, which represents the reliance on vestibular information. Using multivariate analysis of variance, balance parameters were compared between patients with vestibular dysfunction and healthy subjects. Robust regression was used to investigate correlations between gaze stabilization and the vestibular weight. Our results showed that the vestibular weight was smaller in patients with vestibular dysfunction than in healthy subjects (F?=?7.67, p?=?0.011). The vestibular weight during 0.5° peak-to-peak support surface rotations decreased with increasing spontaneous nystagmus eye velocity (??=?-0.82, p?<?0.001). In addition, the vestibular weight during 0.5° and 1.0° peak-to-peak support surface rotations decreased with increasing ocular response bias during rotational chair testing (??=?-0.72, p?=?0.02 and ??=?-0.67, p?=?0.04, respectively). These findings suggest that the reliance on vestibular information during standing balance control decreases with the severity of vestibular dysfunction. We conclude that particular gaze stabilization tests may be used to predict the effect of vestibular dysfunction on standing balance control.

Project description:BackgroundBalance impairment is one of the most distressing symptoms in Parkinson's disease (PD) even with pharmacological treatment (levodopa). A complementary treatment is high frequency stimulation in the subthalamic nucleus (STN). Whether STN stimulation improves postural control is under debate. The aim of this study was to explore the effects of STN stimulation alone on balance performance as assessed with clinical performance tests, subjective ratings of fear of falling and posturography.MethodsTen patients (median age 66, range 59-69 years) with bilateral STN stimulation for a minimum of one year, had their anti-PD medications withdrawn overnight. Assessments were done both with the STN stimulation turned OFF and ON (start randomized). In both test conditions, the following were assessed: motor symptoms (descriptive purposes), clinical performance tests, fear of falling ratings, and posturography with and without vibratory proprioceptive disturbance.ResultsSTN stimulation alone significantly (p = 0.002) increased the scores of the Berg balance scale, and the median increase was 6 points. The results of all timed performance tests, except for sharpened Romberg, were significantly (p <or= 0.016) improved. The patients rated their fear of falling as less severe, and the total score of the Falls-Efficacy Scale(S) increased (p = 0.002) in median with 54 points. All patients completed posturography when the STN stimulation was turned ON, but three patients were unable to do so when it was turned OFF. The seven patients with complete data showed no statistical significant difference (p values >or= 0.109) in torque variance values when comparing the two test situations. This applied both during quiet stance and during the periods with vibratory stimulation, and it was irrespective of visual input and sway direction.ConclusionIn this sample, STN stimulation alone significantly improved the results of the clinical performance tests that mimic activities in daily living. This improvement was further supported by the patients' ratings of fear of falling, which were less severe with the STN stimulation turned ON. Posturography could not be performed by three out of the ten patients when the stimulation was turned OFF. The posturography results of the seven patients with complete data showed no significant differences due to STN stimulation.

Project description:BackgroundFear of falling (FOF) negatively affects health-related quality of life and is common in neurogeriatric patients, however, related parameters are not well understood. This study investigated the relationship between FOF, physical performance (as assessed with the Short Physical Performance Battery and its subscores) and other aspects of sarcopenia in a sample of hospitalized neurogeriatric patients.MethodsIn 124 neurogeriatric patients, FOF was assessed with the Falls Efficacy Scale International (FES-I). Physical performance was measured using the Short Physical Performance Battery (SPPB) including walking duration, balance and five times sit-to-stand task (5xSST) subscores. Appendicular skeletal muscle mass (ASMM) was estimated with the cross-validated Sergi equation using Bioelectrical impedance analysis measures. The Depression im Alter-Skala (DIA-S) was used to assess depressive symptoms. Multiple regression models with FES-I score as outcome variable were computed using backward selection with AICc as selection criterion, including: (i) SPPB total score, ASMM/height2, grip strength, age, gender, positive fall history, number of medications, use of a walking aid, DIA-S score and Montreal Cognitive Assessment (MoCA) score; and (ii) SPPB subscores, ASMM/height2, grip strength, age, gender, positive fall history, number of medications, DIA-S score and MoCA score, once with and once without including use of a walking aid as independent variable.ResultsLower SPPB total score, as well as lower SPPB balance and 5xSST subscores were associated with higher FES-I scores, but SPPB walking duration subscore was not. Moreover, DIA-S, number of medications and use of a walking aid were significantly associated with FOF.ConclusionOur preliminary results suggest that -if confirmed by subsequent studies- it may be worthwhile to screen patients with low SPPB balance and 5xSST subscores for FOF, and to treat especially these mobility deficits in neurogeriatric patients with FOF. Moreover, training neurogeriatric patients to use their walking aids correctly, critical evaluation of medication and treating depressive symptoms may further help reduce FOF in this highly vulnerable cohort.

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The effect of fear of falling on vestibular feedback control of balance.

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