Eye-head coordination during postural perturbation as a predictor of falls in community-dwelling elderly women

Vestibulo-Ocular Reflex Suppression: Clinical Relevance and Assessment in the Digital Age

Background

Visual acuity and image stability are crucial for daily activities, particularly during head motion. The vestibulo-ocular reflex (VOR) and its suppression (VORS) support stable fixation of objects of interest. The VOR drives a reflexive eye movement to counter retinal slip of a stable target during head motion. In contrast, VORS inhibits this countermovement when the target stimulus is in motion. The VORS allows for object fixation when it aligns with the direction of the head's movement, or when an object within or outside the peripheral vision needs to be focused upon.

Summary

Deficits of the VORS have been linked to age-related diseases such as balance deficits associated with an increased fall risk. Therefore, the accurate assessment of the VORS is of particular clinical relevance. However, current clinical assessment methods for VORS are mainly qualitative and not sufficiently standardised. Recent advances in digital health technology, such as smartphone-based videooculography, offer a promising alternative for assessing VORS in a more accessible, efficient, and quantitative manner. Moreover, integrating mobile eye-tracking technology with virtual reality environments allows for the implementation of controlled VORS assessments with different visual inputs. These assessment approaches allow the extraction of novel parameters with potential pathomechanistic and clinical relevance.

Key Messages

We argue that researchers and clinicians can obtain a more nuanced understanding of this ocular stabilisation reflex and its associated pathologies by harnessing digital health technology for VORS assessment. Further research is warranted to explore the technologies' full potential and utility in clinical practice.

Aging

This chapter reviews studies that have examined age-related anatomic and functional changes in sensory, neuromuscular, and cognitive systems that impair the control of balance and gait. Specifically, we examine age-related changes in peripheral systems: lower-limb sensation, visual functions such as contrast sensitivity and depth perception, vestibular sense, strength, and power in the lower-limb muscle groups, as well as central factors including processing speed and executive functioning. Significant impairments in any one of the above systems can predispose older people to falls, with the risk of falling increasing substantially with the number of impairments present. There is increasing evidence that interventions aimed at addressing specific sensory and neuromuscular impairments can improve balance control and reduce fall risk. In particular, task-specific exercise can improve muscle strength, balance, gait and mobility and prevent falls in older people.

Association between vestibulo-ocular reflex suppression, balance, gait, and fall risk in ageing and neurodegenerative disease: protocol of a one-year prospective follow-up study

Background

Falls frequency increases with age and particularly in neurogeriatric cohorts. The interplay between eye movements and locomotion may contribute substantially to the occurrence of falls, but is hardly investigated. This paper provides an overview of current approaches to simultaneously measure eye and body movements, particularly for analyzing the association of vestibulo-ocular reflex (VOR) suppression, postural deficits and falls in neurogeriatric risk cohorts. Moreover, VOR suppression is measured during head-fixed target presentation and during gaze shifting while postural control is challenged. Using these approaches, we aim at identifying quantitative parameters of eye-head-coordination during postural balance and gait, as indicators of fall risk.

Methods/Design

Patients with Progressive Supranuclear Palsy (PSP) or Parkinson’s disease (PD), age- and sex-matched healthy older adults, and a cohort of young healthy adults will be recruited. Baseline assessment will include a detailed clinical assessment, covering medical history, neurological examination, disease specific clinical rating scales, falls-related self-efficacy, activities of daily living, neuro-psychological screening, assessment of mobility function and a questionnaire for retrospective falls. Moreover, participants will simultaneously perform eye and head movements (fixating a head-fixed target vs. shifting gaze to light emitting diodes in order to quantify vestibulo-ocular reflex suppression ability) under different conditions (sitting, standing, or walking). An eye/head tracker synchronized with a 3-D motion analysis system will be used to quantify parameters related to eye-head-coordination, postural balance, and gait. Established outcome parameters related to VOR suppression ability (e.g., gain, saccadic reaction time, frequency of saccades) and motor related fall risk (e.g., step-time variability, postural sway) will be calculated. Falls will be assessed prospectively over 12 months via protocols and monthly telephone interviews.

Discussion

This study protocol describes an experimental setup allowing the analysis of simultaneously assessed eye, head and body movements. Results will improve our understanding of the influence of the interplay between eye, head and body movements on falls in geriatric high-risk cohorts.

Electronic supplementary material

The online version of this article (doi:10.1186/s12883-015-0447-5) contains supplementary material, which is available to authorized users.

Risk factors for falls in multiple sclerosis: an observational study

Background:

People with multiple sclerosis (MS) experience frequent falls, which are associated with impairments and limitations to activities and participations.

Objective:

The objective of this paper is to evaluate falls risk factors using robust clinical measures.

Methods:

A total of 150 individuals (confirmed MS diagnosis, Expanded Disability Status Scale (EDSS) 3.5–6.5) were recruited, with 148 participants included in the final analysis. Demographic data were collected and performance assessed in eight predictor measures (Physiological Profile Assessment (PPA), Brief Ataxia Rating scale, Ashworth scale (Ashworth), Modified Falls Efficacy scale, Symbol Digit Modalities Test, dual-task interference, lying/standing blood pressure, static/dynamic visual acuity). Participants prospectively recorded falls over three months using a daily diary. People were classified as “fallers” based on reports of ≥ two falls.

Results:

A total of 104 participants recorded 672 falls; 78 (52.7%) reported ≥ two falls. Continence issues, previous falls history and use of prescribed medications were each associated with increased risk of being a “faller”. Ashworth and PPA risk score contributed significantly to a logistic regression model predicting faller/non-faller classification. The reduced model (Ashworth, PPA, EDSS) showed fair-to-good predictive ability (ROC c-statistic 0.73, sensitivity 70%, specificity 69%).

Conclusion:

This study confirms the high prevalence of falls in ambulant people with MS. Important potentially modifiable risk factors are identified, suggesting aspects to target in falls interventions.

Perception of the postural vertical and falls in older people

BACKGROUND

Research on the relationship between vestibular function and falls in older people is sparse. The perception of the postural vertical (PPV) provides an indicator measure of vestibular (otolith) function in the absence of visual input and diminished somatosensory feedback.

OBJECTIVE

This study examined whether impaired PPV is associated with falls in this group.

METHODS

One hundred and ninety-five people aged 70 plus years stood blindfolded on a motorised platform that could be tilted in the roll plane and attempted to adjust it so that their bodies were aligned to the vertical. Somatosensory feedback was minimised as the base and vertical support surfaces on the tilting platform were covered in thick soft foam rubber. PPV error from true vertical and PPV variability (°) were calculated. Participants also underwent an assessment of distal tactile sensitivity and the physiological profile assessment (PPA); fallers were defined as those who had one or more falls during a prospective 12-month follow-up period.

RESULTS

Eighty-eight participants (45%) reported falling in the follow-up year. Increased PPV error and variability were correlated with increased lateral sway in a condition of absent visual input and reduced foot somatosensory feedback (eyes closed/foam; r range = 0.16-0.20, p < 0.05) and with composite PPA fall risk scores (r range = 0.22-0.26, p < 0.05). PPV variability was a significant and independent predictor of falls after adjusting for the composite PPA scores, age and gender [adjusted RR = 1.42 (1.01-1.98)].

CONCLUSIONS

Older people with increased PPV variability are at increased risk of falls. These findings indicate that assessment of PPV may augment fall risk assessments in older people.

Sensory system function and postural stability in men aged 30-80 years

OBJECTIVE

To examine age-related changes in postural stability and sensory system functioning in men aged 30-80 years.

DESIGN

Observational, cross-sectional study.

METHODS

One hundred six healthy men aged 30-80 years participated. Personal characteristics were recorded and outcome measures included: velocity of sway during bilateral stance on a firm and foam surface (eyes open (EO) and eyes closed (EC)), balancing on one leg (EO and EC), lower limb somatosensation (tactile acuity, vibration threshold and joint position error), high-contrast visual acuity (HCVA) and low-contrast visual acuity (LCVA), edge contrast sensitivity and vestibular-ocular reflex (VOR) control.

RESULTS

Men in their 60s and 70s were found to be less stable than the younger age decades when standing on a firm or foam surface. Reduced stability was evident from the 40s to 50s for one-leg-stance (EC). Lower limb somatosensation and HCVA and LCVA were significantly reduced by the 60s but edge contrast sensitivity reduced by the 50s. Age-related changes in VOR control did not emerge until the 70s in this study cohort.

CONCLUSIONS

The results show reduction in postural stability and sensory system functioning in men by the 60s supporting pre-emptive assessment of workers in industries where falls are frequent.

What is the role of falls?

There is now firm evidence to support interventions in the prevention of falls in older people, and emerging data support prevention of falls as a method of fracture prevention. This chapter discusses the epidemiology of falls, risk factors associated with an increased risk of falling, assessment of the older faller, and evidence-based approaches to the prevention of falls in the older person. Several randomized controlled trials have found that hip protectors, if worn, probably prevent hip fractures, but that poor compliance is a major issue limiting the effectiveness of this form of intervention. More data are needed to support the role of prevention of falls in preventing fractures, as well as comparative cost-effectiveness data with other evidence-based approaches to preventing fractures in an older population.

Head control: volitional aspects of rehabilitation training in patients with multiple sclerosis compared with healthy subjects

OBJECTIVE

To investigate the role of voluntary mechanisms and motor learning in head stability and the impact of longitudinal biofeedback training in head control.

DESIGN

Crossover trial and single-subject research design.

SETTING

Neurorehabilitation research institute.

PARTICIPANTS

Head stability during treadmill gait was measured in healthy subjects and patients with multiple sclerosis (MS).

INTERVENTION

The experimental condition in which subjects walked on the treadmill was compared with that in which the head was voluntarily stabilized. In another experimental condition, augmented feedback of head displacement was provided by means of a laser mounted on the head that projected a laser beam on a screen. The motor learning was investigated with biofeedback training sessions. Positional feedback was represented by the laser beam, with subjects having to stabilize the beam while walking on the treadmill.

MAIN OUTCOME MEASURE

Head angular oscillation in the sagittal and frontal planes.

RESULTS

Results showed that on verbal request, healthy subjects and patients further stabilized the head during gait, especially in the sagittal plane. Short-term feedback of head displacement was no better than self-stabilization at improving head control. Conversely, the motor learning was evident in the rehabilitation protocol: after 10 to 15 training sessions, patients with MS showed a clinically relevant decrease of head angular oscillations.

CONCLUSIONS

Voluntary mechanisms play a role in head stabilization during gait. Augmented biofeedback of head displacement may be effective in reducing head oscillations.

Incidence, circonstances et conséquences des chutes chez les patients en rééducation après un premier accident vasculaire cérébral

OBJECTIVES

To describe the incidence, circumstances, and consequences of falls in patients admitted in a rehabilitation ward after a stroke.

METHODS

Prospective monitoring of falls over four years in a neurological rehabilitation unit. Use of fall registry.

INCLUSION CRITERIA

age < 75 years, admission < 45 days after stroke onset, single stroke of 1 cerebral hemisphere (nonlacunar) or of the brain stem. Only falls due to loss of balance were considered; falls caused by a seizure or syncope were not considered.

RESULTS

Of 217 consecutive patients with the inclusion criteria, 34 had fallen at least once (15.7%) and 10 twice (4.1%). Fall incidence, defined as the number of falls per patient per day was 2.2 per thousand. Half of the patients fell the first three weeks after admission. Most falls involved getting to or from the wheelchair or the bed; 1 patient had recovered minimal postural abilities at the gym but was not independent. Traumatic lesions were noted in 13 patients: they were minor in nine and severe in four, including three fractures.

CONCLUSION

Falls due to loss of balance are a major problem in patients undergoing rehabilitation after a stroke. Getting to and from wheelchairs in the bedroom and bathroom by patients who are not allowed to do so play a key role in many falls. Prevention programs should consider this information.