Background and Purpose. The Functional Gait Assessment (FGA) is a 10-item gait assessment based on the Dynamic Gait Index. The purpose of this study was to evaluate the reliability, internal consistency, and validity of data obtained with the FGA when used with people with vestibular disorders. Subjects. Seven physical therapists from various practice settings, 3 physical therapist students, and 6 patients with vestibular disorders volunteered to participate. Methods. All raters were given 10 minutes to review the instructions, the test items, and the grading criteria for the FGA. The 10 raters concurrently rated the performance of the 6 patients on the FGA. Patients completed the FGA twice, with an hour's rest between sessions. Reliability of total FGA scores was assessed using intraclass correlation coefficients (2,1). Internal consistency of the FGA was assessed using the Cronbach alpha and confirmatory factor analysis. Concurrent validity was assessed using the correlation of the FGA scores with balance and gait measurements. Results. Intraclass correlation coefficients of .86 and .74 were found for interrater and intrarater reliability of the total FGA scores. Internal consistency of the FGA scores was .79. Spearman rank order correlation coefficients of the FGA scores with balance measurements ranged from .11 to .67. Discussion and Conclusion. The FGA demonstrates what we believe is acceptable reliability, internal consistency, and concurrent validity with other balance measures used for patients with vestibular disorders.

Reliability, internal consistency, and validity of data obtained with the functional gait assessment.

Trunk and head movements were characterized over a wide range of walking speeds to determine the relationship between stride length, stepping frequency, vertical head translation, pitch rotation of the head, and pitch trunk rotation as a function of gait velocity. Subjects (26-44 years old) walked on a linear treadmill at velocities of 0.6-2.2 m/s. The head and trunk were modeled as rigid bodies, and rotation and translation were determined using a video-based motion analysis system. At walking speeds up to 1.2 m/s there was little head pitch movement in space, and the head pitch relative to the trunk was compensatory for trunk pitch. As walking velocity increased, trunk pitch remained approximately invariant, but a significant head translation developed. This head translation induced compensatory head pitch in space, which tended to point the head at a fixed point in front of the subject that remained approximately invariant with regard to walking speed. The predominant frequency of head translation and rotation was restricted to a narrow range from 1.4 Hz at 0.6 m/s to 2.5 Hz at 2.2 m/s. Within the range of 0.8-1.8 m/s, subjects tended to increase their stride length rather than step frequency to walk faster, maintaining the predominant frequency of head movement at close to 2.0 Hz. At walking speeds above 1.2 m/s, head pitch in space was highly coherent with, and compensatory for, vertical head translation. In the range 1.2-1.8 m/s, the power spectrum of vertical head translation was the most highly tuned, and the relationship between walking speed and head and trunk movements was the most linear. We define this as an optimal range of walking velocity with regard to head-trunk coordination. The coordination of head and trunk movement was less coherent at walking velocities below 1.2 m/s and above 1.8 m/s. These results suggest that two mechanisms are utilized to maintain a stable head fixation distance over the optimal range of walking velocities. The relative contribution of each mechanism to head orientation depends on the frequency of head movement and consequently on walking velocity. From consideration of the frequency characteristics of the compensatory head pitch, we infer that compensatory head pitch movements may be produced predominantly by the angular vestibulocollic reflex (aVCR) at low walking speeds and by the linear vestibulocollic reflex (1VCR) at the higher speeds.

Effects of walking velocity on vertical head and body movements during locomotion

To identify vestibular influences on human walking, galvanic vestibular stimulation was applied to normal adult subjects as they walked to a previously seen target. A transmastoidal step stimulus commenced as subjects started walking. With the eyes shut, the galvanic stimulus caused large turns towards the side with the anodal current.


Ability to perceive the trajectory of gait without visual cues was measured by guiding blindfolded subjects from one arbitrary point to another, either walking or seated in a wheelchair. On reaching a destination position and removing the blindfold, subjects pointed to indicate the starting position. Subjects made considerable errors in estimating the trajectory, but were equally accurate whether in the wheelchair or walking.


To determine the effects of vestibular stimulation on the perception of trajectory, the galvanic stimulus was applied to blindfolded subjects as they were guided from one point to another in the wheelchair. The vestibular stimulus produced an illusory shift in the trajectory travelled. This shift was towards the side with the cathode, i.e. in the opposite direction to the turn produced by the stimulus during walking.


We conclude that galvanic vestibular stimulation during walking causes subjects to turn from their planned trajectory. In part, this altered course may compensate for an altered perception of trajectory produced by the stimulus. However, altered perception of the vertical or the base of support, or direct vestibulo-fugal influences on the leg muscles could contribute to the changes in gait.







When we walk towards a destination it is neither necessary nor common for us to keep our vision continuously fixed on the target. Once a target has been seen, it is possible to shut the eyes and walk directly to it if it is not too distant. In this situation, proprioceptive sensory inputs from the limbs and the vestibular organs provide information about the trajectory and stability of the body. Proprioceptive input from muscles and joints of the pelvis and hips can contribute to the sensation of the trajectory walked (Gordon et al. 1995). The vestibular organs provide signals about both the linear and angular acceleration of the head in space, and could also contribute to a sensation of trajectory if the frequency and acceleration of normal walking are appropriate. Patients who suffer pathological vestibular disorders commonly stagger and turn to one side. This is likely to arise from an inability to maintain vertical balance as shown by their similar problem when standing. However, an altered perception of trajectory might also contribute to this deviation from the intended path.

Human standing is thought to depend on a combined reflex response to proprioceptive, visual and vestibular sensory inputs. Vestibular input is not necessary to provide postural responses to correct the natural sway and perturbations of standing (Fitzpatrick et al. 1992) and does not contribute to the perception of sway during standing (Fitzpatrick & McCloskey, 1994). However, when vestibular input is inappropriate because of vestibular pathology or vestibular stimulation, stable standing is compromised.

In standing human subjects, galvanic vestibular stimulation evokes a prolonged ‘galvanic body sway’ (Coates, 1973) and transient electromyographic (EMG) responses in the leg muscles (Nashner & Wolfson, 1974; Britton et al. 1993). When a stimulus current is passed between the mastoid processes so that the current is anodal on one side and cathodal on the other, subjects sway towards the direction of the anode. If the head is facing forward subjects sway laterally, but if the head is turned to face the side, sway is in the antero-posterior plane. In part, this body sway might be a reaction to a perception of sway in the opposite direction that can be evoked by galvanic vestibular stimulation (Fitzpatrick et al. 1994). Other studies using galvanic vestibular stimulation in standing subjects suggest that the vestibular system establishes an internal vertical reference (Inglis et al. 1995), or is organized to keep the centre of mass of the body within safe limits relative to the area of foot contact with the ground (Day et al. 1997).

Like standing, human walking is a state of unstable equilibrium in which the body is balanced over a limited area of support. Standing approximates a state of static equilibrium with the centre of mass of the body kept above the area of the feet. Although walking represents a more complex dynamic equilibrium, it is analogous to standing in imposing restrictions on the position, velocity and acceleration of the body in relation to the moving base of support of the feet.

The present experiments investigate in normal subjects: (i) the effects of galvanic vestibular stimulation during walking, and (ii) the vestibular and proprioceptive contributions to the perceptions of a walked trajectory. The results show that at ordinary walking speeds, the perception of trajectory can be based on vestibular input, and that the availability of proprioceptive input related to walking does not further improve the accuracy of the perception of trajectory. During walking galvanic vestibular stimulation causes subjects to turn from a planned trajectory. Altered perception could contribute to this deviation.

https://physoc.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-7793.1999.0931s.x

Effects of galvanic vestibular stimulation during human walking

Vertigo. Its Multisensory Syndromes , 2nd Edition. By thomas brand. (Pp 503, US$249.00). Published by Springer, Heidelberg, 1999. ISBN 3-540-19934-9.

Thomas Brandt's masterpiece Vertigo remains mandatory reading for clinicians interested in this symptom. The basic sciences underpinning vertigo, together with the clinical diagnosis and management of all disorders characterised by this symptom, are comprehensively reported, extensively referenced, and beautifully illustrated. The book is detailed and exhaustive in its subject matter. The only area which seems to have been omitted in any depth is that of the cardiovascular causes of dizziness and vertigo.

There is a broad introduction covering the pathophysiology underpinning vestibular disorders, vertigo, dizziness, and falls; the clinical assessment of such a patient; and the management strategies, together with their rationale. Common disorders—namely, acute peripheral vestibular episodes and Meniere's disease, are well covered, in addition to the rarer …

Vertigo. Its Multisensory Syndromes

Unilateral long-lasting vibration was applied to the sternomastoid muscle to assess the influence of asymmetric neck proprioceptive input on body orientation during stepping-in-place. Blindfolded s...

https://www.physiology.org/doi/pdf/10.1152/jn.00198.2002

Neck muscle vibration and spatial orientation during stepping in place in humans

The purpose of this study was to clarify the role of the vestibular system in human locomotion. The subjects were nine healthy controls, nine patients with unilateral vestibular deficiency (UVD) and nine patients with bilateral vestibular deficiency (BVD). The UVD subjects were Meniere's disease patients who were being treated with administration of gentamicin into the tympanic cavity. BVD subjects were hearing-impaired individuals who showed no response to the ice-water caloric test. A total of 13 markers were attached to the head, trunk (C7), hip and foot in order to measure translational and rotational motions with the aid of a video image processing system. All subjects were instructed to restrict their stride length to 80 cm while walking on a treadmill and watching a visual target. However, walking speed varied depending on the ability of the subject to maintain body equilibrium. The results showed that walking speed and step frequency were significantly lower for the UVD and BVD groups than for the...

Three-dimensional analysis of human locomotion in normal subjects and patients with vestibular deficiency.

Human locomotion was analysed in the sagittal and coronal planes using a position detector system composed of 2 infrared video cameras and a data processor. Normal healthy volunteers with 8 marker points on the body were asked to walk in place (WIP) and on a treadmill (WOT). Vertical and medial/lateral (M/L) translational movements were measured. Head angular movements in the sagittal (pitch) and coronal (roll) planes were also analysed. Pitch movements counteracted the vertical head movements. Head movement was remarkably attenuated in the vertical axis compared with that of the trunk. However, head M/L movement showed no difference with that of the lower part of the body. Ice water caloric stimulation was introduced to cause acute unilateral vestibular deficit. The stride length and step cycle became small after caloric stimulation in WOT, but not in WIP. The characteristic change in locomotive pattern was a large lateral sway of the hip joint occurring to the side away from calorization (right) during one foot standing (right foot) (t-test, p = 0.057). Measurement of M/L sway amplitude showed an increase only at the hip joint. As the changes in head and neck movements were not significant after caloric stimulation, it appears that the vestibulo-spinal reflex contributes little to maintaining the dynamic balance of the upper body. The importance of the hip joint for locomotion (hip strategy) was confirmed from the present data.

3D Analysis of Human Locomotion Before and After Caloric Stimulation

Effects of caloric vestibular stimulation on head and trunk movements during walking.

Linear acceleration (CF) caused by centrifugal force results in ocular deviation and change in spatial orientation. Thirteen healthy human subjects and one labyrinthine defective (LD) subject were exposed to CF to examine the change in spatial orientation and eye position. CF was applied by rotating the subject at a 90 cm off-center position (eccentric rotation). Constant angular velocities of 80, 100, 120 and 140 deg/sec depicted CF of 0.18 to 0.55 G. CF was introduced in two chair positions as it affects along the inter-aural (X) or naso-occipital (Y) axes. Subjects were asked to adjust an LED bar to a perpendicular position while the chair was rotated in the darked room. Judgement for visual vertical was very accurate when the chair was stationary (with deviation of the bar within 1.1 degrees). Under CF along the X-axis, judgement for subjective perpendicular changed (i.e., toward the center of rotation). Amplitude of the tilting angle significantly increased as a function of CF (ANOVA, p<0.05). However, no significant change in bar deviation was found in one LD subject during the rotation. Also, CF along the Yaxis did not cause any significant deviation of the bar in healthy volunteers. Eye movement during eccentric rotation was analyzed by using an infrared video camera and computer analyzing system. Torsional eye deviations with amplitudes of 0.1 to 1.5 degrees were detected under CF along the X-axis. Under CF along the Y-axis, upward eye deviations with amplitudes of 1.6 to 3.2 degrees were detected. As the amplitude of eye deviation was very small in both conditions, it is assumed that the gain of otolithocular reflex had only a small gain. The linear acceleration acting upon the head had a larger influence upon spatial orientation than upon the oculomotor system.

Effects of Centrifugal Force upon Spatial Orientation and Eye Position in Human Subjects

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Three-dimensional analysis of human locomotion in normal subjects and patients with vestibular deficiency.

3D Analysis of Human Locomotion Before and After Caloric Stimulation

Effects of caloric vestibular stimulation on head and trunk movements during walking.

Effects of Centrifugal Force upon Spatial Orientation and Eye Position in Human Subjects