Continuous Head Motion is a Greater Motor Control Challenge than Transient Head Motion in Patients with Loss of Vestibular Function

Background. The vestibular system is vital for gaze stability via the vestibulo-ocular reflex, which generates compensatory eye motion in the direction opposite to head motion. Consequently, individuals with peripheral vestibular loss demonstrate impaired gaze stability that reduces functional capacity and quality of life. To facilitate patients’ compensatory strategies, two classes of gaze stabilization exercises are often prescribed: (i) transient (eg, ballistic) and (ii) continuous. However, the relative benefits of these two classes of exercises are not well understood. Objective. To quantify head motion kinematics in patients with vestibular loss while they performed both classes of exercises. Methods. Using inertial measurement units, head movements of 18 vestibular schwannoma patients were measured before and after surgical deafferentation and compared with age-matched controls. Results. We found that the head movement during both classes of exercises paralleled those of natural head movement recorded during daily activities. However, head movement patterns were more informative for continuous than transient exercises in distinguishing patients from healthy controls. Specifically, we observed coupling between kinematic measures in control subjects that was absent in patients for continuous but not transient head motion exercises. In addition, kinematic measures (eg, cycle duration) were predictive of standard clinical measures for continuous but not transient head motion exercises. Conclusions. Our data suggest that performing continuous head motion is a greater motor control challenge than transient head motion in patients with less reliable vestibular feedback during the sub-acute stage of recovery, which may also prove to be a reliable measure of progression in vestibular rehabilitation protocols.

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Effects of vestibular neurectomy and neural compensation on head movements in patients undergoing vestibular schwannoma resection

Scientific Reports ◽

10.1038/s41598-020-79756-3 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Omid A. Zobeiri ◽

Gavin M. Mischler ◽

Susan A. King ◽

Richard F. Lewis ◽

Kathleen E. Cullen

Keyword(s):

Vestibular Schwannoma ◽

Normal Subjects ◽

Head Movements ◽

Head Motion ◽

Vestibular Loss ◽

Vestibular Neurectomy ◽

Time Points ◽

Head Kinematics ◽

Kinematic Measures ◽

Vestibular Damage

AbstractThe vestibular system is vital for maintaining balance and stabilizing gaze and vestibular damage causes impaired postural and gaze control. Here we examined the effects of vestibular loss and subsequent compensation on head motion kinematics during voluntary behavior. Head movements were measured in vestibular schwannoma patients before, and then 6 weeks and 6 months after surgical tumor removal, requiring sectioning of the involved vestibular nerve (vestibular neurectomy). Head movements were recorded in six dimensions using a small head-mounted sensor while patients performed the Functional Gait Assessment (FGA). Kinematic measures differed between patients (at all three time points) and normal subjects on several challenging FGA tasks, indicating that vestibular damage (caused by the tumor or neurectomy) alters head movements in a manner that is not normalized by central compensation. Kinematics measured at different time points relative to vestibular neurectomy differed substantially between pre-operative and 6-week post-operative states but changed little between 6-week and > 6-month post-operative states, demonstrating that compensation affecting head kinematics is relatively rapid. Our results indicate that quantifying head kinematics during self-generated gait tasks provides valuable information about vestibular damage and compensation, suggesting that early changes in patient head motion strategy may be maladaptive for long-term vestibular compensation.

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Active head movements facilitate compensation for effects of prism displacement on dynamic gait12

Journal of Vestibular Research ◽

10.3233/ves-2006-161-203 ◽

2006 ◽

Vol 16 (1-2) ◽

pp. 29-33

Author(s):

Kim R. Gottshall ◽

Michael E. Hoffer ◽

Helen S. Cohen ◽

Robert J. Moore

Keyword(s):

Head Movement ◽

Sensory Modality ◽

Normal Subjects ◽

The Body ◽

Head Movements ◽

Head Motion ◽

Control Group ◽

Entire Body ◽

Group 3 ◽

Group 2

Study design: Four groups, between-subjects study. Objectives: To investigate the effects of exercise on adaptation of normal subjects who had been artificially spatially disoriented. Background: Many patients referred for rehabilitation experience sensory changes, due to age or disease processes, and these changes affect motor skill. The best way to train patients to adapt to these changes and to improve their sensorimotor skills is unclear. Using normal subjects, we tested the hypothesis that active, planned head movement is needed to adapt to modified visual input. Methods and measures: Eighty male and female subjects who had normal balance on computerized dynamic posturography (CDP) and the dynamic gait index (DGI), were randomly assigned to four groups. All groups donned diagonally shift lenses and were again assessed with CDP and DGI. The four groups were then treated for 20 min. Group 1 (control group) viewed a video, Group 2 performed exercise that involved translating the entire body through space, but without separate, volitional head movement, Group 3 performed exercises which all incorporated volitional, planned head rotations, and Group 4 performed exercises that involved translating the body (as in Group 2) and incorporated volitional, planned head motion (as in Group 3). All subjects were post-tested with CDP and DGI, lenses were removed, and subjects were retested again with CDP and DGI. Results: The groups did not differ significantly on CDP scores but Groups 3 and 4 had significantly better DGI scores than Groups 1 and 2. Conclusions: Active head movement that is specifically planned as part of the exercise is more effective than passive attention or head movements that are not consciously planned, for adapting to sensorimotor change when it incorporates active use of the changed sensory modality, in this case head motion.

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Reduced Purposeful Head Movements During Community Ambulation Following Unilateral Vestibular Loss

Neurorehabilitation and Neural Repair ◽

10.1177/1545968318770271 ◽

2018 ◽

Vol 32 (4-5) ◽

pp. 309-316 ◽

Cited By ~ 5

Author(s):

Serene Sulyn Paul ◽

Leland E. Dibble ◽

Raymond G. Walther ◽

Clough Shelton ◽

Richard Klaus Gurgel ◽

...

Keyword(s):

Head Movement ◽

Cross Sectional Study ◽

Head Movements ◽

Healthy Individuals ◽

Cross Sectional ◽

Vestibular Loss ◽

Vestibular Hypofunction ◽

Large Head ◽

Community Ambulation ◽

Measurement Units

Background. Individuals with unilateral vestibular hypofunction (UVH) alter their movement and reduce mobility to try to stabilize their gaze and avoid symptoms of dizziness and vertigo. Objective. To determine if individuals with UVH 6 weeks after surgery demonstrate altered head and trunk kinematics during community ambulation. Methods. A total of 15 vestibular schwannoma patients with documented postoperative unilateral vestibular loss and 9 healthy controls with symmetrical vestibulo-ocular reflexes participated in this cross-sectional study. Head kinematics (head turn frequency, amplitude, and velocity) and head-trunk coordination during community ambulation were obtained from inertial measurement units for all head movements and within specific amplitudes of head movement. Results. Individuals with UVH made smaller (mean 26° [SD = 3°] vs 32° [SD = 6°]), fewer (mean 133 [SD = 59] vs 221 [SD = 64]), and slower (mean 75°/s [SD = 8°/s] vs 103°/s [SD = 23°/s]) head turns than healthy individuals ( P < .05) but did not demonstrate significantly increased head-trunk coupling (mean 38% [SD = 18%] vs 31% [SD = 11%], P = .22). When small (≤45°) and large (>45°) head turns were considered separately, individuals with UVH demonstrated increased head-trunk coupling compared with healthy individuals for large head turns (mean 54% [SD = 23%] vs 33% [SD = 10%], P = .005). Conclusions. This study demonstrated that although walking at an adequate speed, individuals with UVH made fewer, smaller, and slower head movements symmetrically in both directions compared with healthy individuals and did not decouple their head movement relative to their trunk when required to make larger purposeful head turns during community ambulation.

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Vestibular Gaze Stabilization: Different Behavioral Strategies for Arboreal and Terrestrial Avians

Journal of Neurophysiology ◽

10.1152/jn.00966.2004 ◽

2005 ◽

Vol 93 (3) ◽

pp. 1165-1173 ◽

Cited By ~ 22

Author(s):

Asim Haque ◽

J. David Dickman

Keyword(s):

Avian Species ◽

Head Movements ◽

Head Motion ◽

Behavioral Strategies ◽

Specific Behavior ◽

Gaze Stabilization ◽

High Frequencies ◽

Gaze Stability ◽

Species Specific

In birds, it is thought that head movements play a major role in the reflexive stabilization of gaze and vision. In this study, we investigated the contributions of the eye and head to gaze stabilization during rotations under both head-fixed [vestibuloocular (VOR)] and head-free conditions in two avian species: pigeons and quails. These two species differ both in ocular anatomy (the pigeon has 2 distinct foveal regions), as well as in behavioral repertoires. Pigeons are arboreal, fly extended distances, and can navigate. Quails are primarily engrossed in terrestrial niches and fly only short distances. Unlike the head-fixed VOR gains that were under-compensatory for both species, gaze gains under head-free conditions were completely compensatory at high frequencies. This compensation was achieved primarily with head movements in pigeons, but with combined head and eye-in-head contributions in the quail. In contrast, eye-in-head motion, which was significantly reduced for head-free compared with head-fixed conditions, contributed very little to overall gaze stability in pigeons. These results suggest that disparity between the stabilization strategies employed by these two birds may be attributed to differences in species-specific behavior and anatomy.

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Head movement kinematics are altered during gaze stability exercises in vestibular schwannoma patients

Scientific Reports ◽

10.1038/s41598-021-86533-3 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Lin Wang ◽

Omid A. Zobeiri ◽

Jennifer L. Millar ◽

Michael C. Schubert ◽

Kathleen E. Cullen

Keyword(s):

Standard Of Care ◽

Head Movements ◽

Vestibular Loss ◽

Gaze Stabilization ◽

Head Kinematics ◽

Gaze Stability ◽

Post Surgery ◽

Before And After ◽

Healthy Control ◽

Clinical Measures

AbstractGaze stability is the ability of the eyes to fixate a stable point when the head is moving in space. Because gaze stability is impaired in peripheral vestibular loss patients, gaze stabilization exercises are often prescribed to facilitate compensation. However, both the assessment and prescription of these exercises are subjective. Accordingly, here we quantified head motion kinematics in patients with vestibular loss while they performed the standard of care gaze stability exercises, both before and after surgical deafferentation. We also correlate the head kinematic data with standard clinical outcome measures. Using inertial measurement units, we quantified head movements in patients as they transitioned through these two vestibular states characterized by different levels of peripheral damage. Comparison with age-matched healthy control subjects revealed that the same kinematic measurements were significantly abnormal in patients both pre- and post-surgery. Regardless of direction, patients took a longer time to move their heads during the exercises. Interestingly, these changes in kinematics suggest a strategy that existed preoperatively and remained symmetric after surgery although the patients then had complete unilateral vestibular loss. Further, we found that this kinematic assessment was a good predictor of clinical outcomes, and that pre-surgery clinical measures could predict post-surgery head kinematics. Thus, together, our results provide the first experimental evidence that patients show significant changes in head kinematics during gaze stability exercises, even prior to surgery. This suggests that early changes in head kinematic strategy due to significant but incomplete vestibular loss are already maladaptive as compared to controls.

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Short-Latency Covert Saccades - The Explanation for Good Dynamic Visual Performance After Unilateral Vestibular Loss?

Frontiers in Neurology ◽

10.3389/fneur.2021.695064 ◽

2021 ◽

Vol 12 ◽

Author(s):

Julia Sjögren ◽

Mikael Karlberg ◽

Craig Hickson ◽

Måns Magnusson ◽

Per-Anders Fransson ◽

...

Keyword(s):

Visual Perception ◽

Head Movement ◽

Position Error ◽

Head Movements ◽

Visual Performance ◽

Head Impulse Test ◽

Vestibular Loss ◽

Intact Side ◽

Head Impulse ◽

Head Impulses

Background: Functional head impulse test (fHIT) tests the ability of the vestibulo-ocular reflex (VOR) to allow visual perception during head movements. Our previous study showed that active head movements to the side with a vestibular lesion generated a dynamic visual performance that were as good as during movements to the intact side.Objective: To examine the differences in eye position during the head impulse test when performed with active and passive head movements, in order to better understand the role of the different saccade properties in improving visual performance.Method: We recruited 8 subjects with complete unilateral vestibular loss (4 men and 4 women, mean age 47 years) and tested them with video Head Impulse Test (vHIT) and Functional Head Impulse Test (fHIT) during passive and active movements while looking at a target. We assessed the mean absolute position error of the eye during different time frames of the head movement, the peak latency and the peak velocity of the first saccade, as well as the visual performance during the head movement.Results: Active head impulses to the lesioned side generated dynamic visual performances that were as good as when testing the intact side. Active head impulses resulted in smaller position errors during the visual perception task (p = 0.006) compared to passive head-impulses and the position error during the visual perception time frame correlated with shorter latencies of the first saccade (p < 0.001).Conclusion: Actively generated head impulses toward the side with a complete vestibular loss resulted in a position error within or close to the margin necessary to obtain visual perception for a brief period of time in patients with chronic unilateral vestibular loss. This seems to be attributed to the appearance of short-latency covert saccades, which position the eyes in a more favorable position during head movements.

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Combined eye-head gaze shifts in the primate. III. Contributions to the accuracy of gaze saccades

Journal of Neurophysiology ◽

10.1152/jn.1990.64.6.1873 ◽

1990 ◽

Vol 64 (6) ◽

pp. 1873-1891 ◽

Cited By ~ 73

Author(s):

R. D. Tomlinson

Keyword(s):

Head Movement ◽

Head Movements ◽

Whole Body ◽

Midsagittal Plane ◽

Gaze Shifts ◽

Gaze Shift ◽

The Gaze ◽

Gaze Stability ◽

Gaze Saccade ◽

Gaze Saccades

1. The behavior of the combined eye-head gaze saccade mechanism was investigated in the rhesus monkey under both normal circumstances and in the presence of perturbations delivered to the head by a torque motor. Animals were trained to follow a target light that stepped at regular intervals through an angle of 68 degrees (+/- 34 degrees with respect to the midsagittal plane). Thus all primary saccades were center crossing. On randomly occurring trials the torque motor was pulsed so as to perturb the trajectory of the head, thus allowing us to assess both the functional state of the vestibuloocular reflex (VOR) and the effects of such perturbations on gaze saccade accuracy (gaze is defined as the sum of eye-in-head plus head-in-space, and a gaze saccade as a combined eye-head saccadic gaze shift). 2. Gaze shifts can be divided into two discrete sections: the portion during which the gaze angle is changing (the saccadic portion), and the portion during which the gaze is stationary but the head continues to move (the terminal head-movement portion). For the system to accurately acquire eccentric targets, at least two criteria must be met: 1) the saccadic portion must be accurate, and 2) the compensatory eye movement that occurs during the terminal head-movement portion must be equal and opposite to the head movement, thereby maintaining gaze stability. Perturbations delivered during the terminal head-movement portion of the gaze shift indicated that VOR was functioning normally, and thus we concluded that the compensatory eye movements that accompany head movements were vestibular in origin. 3. As reported previously, during the saccadic portion of large-amplitude gaze saccades, the VOR ceases to function. In spite of this observation, the accuracy of the gaze saccade is not affected by perturbations delivered to the head. Gaze accuracy is maintained both by changing the duration of the saccadic portion and by altering the head trajectory. 4. Because rhesus monkeys often make very rapid head movements (1,200 degrees/s), we wished to discover the velocity range over which the monkey VOR might be expected to operate. Accordingly, in a second series of experiments, VOR function was assessed during passive whole-body rotations with the head fixed. By the use of spring-assisted manual rotations, peak velocities up to 850 degrees/s were achieved. When VOR gain was measured during such rotations, it was found to be equal to 0.9 up to the maximum velocities used.(ABSTRACT TRUNCATED AT 400 WORDS)

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Role of pinnae and head movements in localizing pure tones 1The authors would like to thank Mr. Remi Humbert for implementing the experiment in Turbo Pascal and for his further assistance.

Swiss Journal of Psychology ◽

10.1024//1421-0185.58.3.170 ◽

1999 ◽

Vol 58 (3) ◽

pp. 170-179 ◽

Cited By ~ 4

Author(s):

Barbara S. Muller ◽

Pierre Bovet

Keyword(s):

Sound Source ◽

Head Movement ◽

Movement Analysis ◽

Head Movements ◽

Sound Sources ◽

Localization Accuracy ◽

Sound Effects ◽

Posterior Quadrant ◽

Localization Performance ◽

Pure Tones

Twelve blindfolded subjects localized two different pure tones, randomly played by eight sound sources in the horizontal plane. Either subjects could get information supplied by their pinnae (external ear) and their head movements or not. We found that pinnae, as well as head movements, had a marked influence on auditory localization performance with this type of sound. Effects of pinnae and head movements seemed to be additive; the absence of one or the other factor provoked the same loss of localization accuracy and even much the same error pattern. Head movement analysis showed that subjects turn their face towards the emitting sound source, except for sources exactly in the front or exactly in the rear, which are identified by turning the head to both sides. The head movement amplitude increased smoothly as the sound source moved from the anterior to the posterior quadrant.

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Two conditions to fully recover dynamic canal function in unilateral peripheral vestibular hypofunction patients

Journal of Vestibular Research ◽

10.3233/ves-201557 ◽

2021 ◽

pp. 1-15

Author(s):

Michel Lacour ◽

Alain Thiry ◽

Laurent Tardivet

Keyword(s):

Crucial Role ◽

Recovery Process ◽

Head Impulse Test ◽

Additional Parameter ◽

Vestibular Loss ◽

Horizontal Canal ◽

Lateral Canal ◽

Gaze Stability ◽

Vestibular Hypofunction ◽

Anterior Canal

BACKGROUND: The crucial role of early vestibular rehabilitation (VR) to recover a dynamic semicircular canal function was recently highlighted in patients with unilateral vestibular hypofunction (UVH). However, wide inter-individual differences were observed, suggesting that parameters other than early rehabilitation are involved. OBJECTIVE: The aim of the study was to determine to what extent the degree of vestibular loss assessed by the angular vestibulo-ocular reflex (aVOR) gain could be an additional parameter interfering with rehabilitation in the recovery process. And to examine whether different VR protocols have the same effectiveness with regard to the aVOR recovery. METHODS: The aVOR gain and the percentage of compensatory saccades were recorded in 81 UVH patients with the passive head impulse test before and after early VR (first two weeks after vertigo onset: N = 43) or late VR (third to sixth week after onset: N = 38) performed twice a week for four weeks. VR was performed either with the unidirectional rotation paradigm or gaze stability exercises. Supplementary outcomes were the dizziness handicap inventory (DHI) score, and the static and dynamic subjective visual vertical. RESULTS: The cluster analysis differentiated two distinct populations of UVH patients with pre-rehab aVOR gain values on the hypofunction side below 0.20 (N = 42) or above 0.20 (N = 39). The mean gain values were respectively 0.07±0.05 and 0.34±0.12 for the lateral canal (p < 0.0001), 0.09±0.06 and 0.44±0.19 for the anterior canal (p < 0.0001). Patients with aVOR gains above 0.20 and early rehab fully recovered dynamic horizontal canal function (0.84±0.14) and showed very few compensatory saccades (18.7% ±20.1%) while those with gains below 0.20 and late rehab did not improve their aVOR gain value (0.16±0.09) and showed compensatory saccades only (82.9% ±23.7%). Similar results were found for the anterior canal function. Recovery of the dynamic function of the lateral canal was found with both VR protocols while it was observed with the gaze stability exercises only for the anterior canal. All the patients reduced their DHI score, normalized their static SVV, and exhibited uncompensated dynamic SVV. CONCLUSIONS: Early rehab is a necessary but not sufficient condition to fully recover dynamic canal function. The degree of vestibular loss plays a crucial role too, and to be effective rehabilitation protocols must be carried out in the plane of the semicircular canals.

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Development of a trunk motor paradigm for use in neuroimaging

Translational Neuroscience ◽

10.1515/tnsci-2020-0116 ◽

2020 ◽

Vol 11 (1) ◽

pp. 193-200

Author(s):

Elizabeth Saunders ◽

Brian C. Clark ◽

Leatha A. Clark ◽

Dustin R. Grooms

Keyword(s):

Motor Control ◽

Maximum Voluntary Contraction ◽

Voluntary Contraction ◽

Erector Spinae ◽

Head Motion ◽

Low Back ◽

Cyclic Contraction ◽

Cyclic Contractions ◽

Measurement Units ◽

Healthy Participants

AbstractThe purpose of this study was to quantify head motion between isometric erector spinae (ES) contraction strategies, paradigms, and intensities in the development of a neuroimaging protocol for the study of neural activity associated with trunk motor control in individuals with low back pain. Ten healthy participants completed two contraction strategies; (1) a supine upper spine (US) press and (2) a supine lower extremity (LE) press. Each contraction strategy was performed at electromyographic (EMG) contraction intensities of 30, 40, 50, and 60% of an individually determined maximum voluntary contraction (MVC) (±10% range for each respective intensity) with real-time, EMG biofeedback. A cyclic contraction paradigm was performed at 30% of MVC with US and LE contraction strategies. Inertial measurement units (IMUs) quantified head motion to determine the viability of each paradigm for neuroimaging. US vs LE hold contractions induced no differences in head motion. Hold contractions elicited significantly less head motion relative to cyclic contractions. Contraction intensity increased head motion in a linear fashion with 30% MVC having the least head motion and 60% the highest. The LE hold contraction strategy, below 50% MVC, was found to be the most viable trunk motor control neuroimaging paradigm.

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