Disequilibrium of unknown cause in older people

Towards an explanation for 'unexplained' dizziness in older people

BACKGROUND

Subjective unsteadiness or dizziness, usually without increase in body sway, is common in older people. The absence of mechanistic understanding of such symptoms renders clinical management difficult. Here, we explore the mechanisms behind such idiopathic dizziness (ID), focusing on postural control abnormalities.

METHODS

Thirty patients with ID and 30 age-matched controls stood on a moving platform. Platform oscillations were randomly delivered at different velocities (from 0 to 0.2 m/s). Markers of postural control, including objective sway (trunk sway path, recorded via a sensor attached to vertebrae C7), stepping responses, subjective instability and anxiety ratings were obtained. MRI scans were available for correlations with levels of cerebral small vessel disease in 28 patients and 24 controls.

RESULTS

We observed a significant relationship between objective and subjective instability in all groups. The slope of this fit was significantly steeper for patients than controls, indicating greater perceived instability for the same body sway. Stepwise linear regression showed that the slopes of this objective-subjective instability relationship were best explained by concerns about falling (Falls Efficacy Scale-International), clinical physical functioning (Short Physical Performance Battery) and, to some degree, by neuroimaging markers of cerebral small vessel disease. In addition, patients had a reduced stepping threshold, suggesting an overly cautious postural response.

CONCLUSION

The distorted perception of instability and subtle impairments in balance control, including abnormal and overly cautious stepping responses, underlies the emergence of ID. It appears to relate to changes in postural performance, psychological functioning and disruption of postural brain networks associated with cerebral small vessel disease.

A link between frontal white matter integrity and dizziness in cerebral small vessel disease

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Idiopathic dizziness in older people is associated with more vascular risk.

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Idiopathic dizziness is also associated with impaired balance and cognition.

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These findings co-occur with more frontal markers of cerebral small vessel disease.

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Small vessel disease may contribute to dizziness through its effects on balance.

One in three older people (>60 years) complain of dizziness which often remains unexplained despite specialist assessment. We investigated if dizziness was associated with vascular injury to white matter tracts relevant to balance or vestibular self-motion perception in sporadic cerebral small vessel disease (age-related microangiopathy). We prospectively recruited 38 vestibular clinic patients with idiopathic (unexplained) dizziness and 36 age-matched asymptomatic controls who underwent clinical, cognitive, balance, gait and vestibular assessments, and structural and diffusion brain MRI. Patients had more vascular risk factors, worse balance, worse executive cognitive function, and worse ankle vibration thresholds in association with greater white matter hyperintensity in frontal deep white matter, and lower fractional anisotropy in the genu of the corpus callosum and the right inferior longitudinal fasciculus. A large bihemispheric white matter network had less structural connectivity in patients. Reflex and perceptual vestibular function was similar in patients and controls. Our results suggest cerebral small vessel disease is involved in the genesis of dizziness through its effect on balance.

Small vessel disease disrupts EEG postural brain networks in 'unexplained dizziness in the elderly'

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Unexplained dizziness in the elderly may result from cerebral small vessel disease.

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Dizzy elderly patients differed from controls in EEG power when standing.

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EEG power when standing correlated with subjective (perceived) instability.

Objective

To examine the hypothesis that small vessel disease disrupts postural networks in older adults with unexplained dizziness in the elderly (UDE).

Methods

Simultaneous electroencephalography and postural sway measurements were undertaken in upright, eyes closed standing, and sitting postures (as baseline) in 19 younger adults, 33 older controls and 36 older patients with UDE. Older adults underwent magnetic resonance imaging to determine whole brain white matter hyperintensity volumes, a measure of small vessel disease. Linear regression was used to estimate the effect of instability on electroencephalographic power and connectivity.

Results

Ageing increased theta and alpha desynchronisation on standing. In older controls, delta and gamma power increased, and theta and alpha power reduced with instability. Dizzy older patients had higher white matter hyperintensity volumes and more theta desynchronisation during periods of instability. White matter hyperintensity volume and delta power during periods of instability were correlated, positively in controls but negatively in dizzy older patients. Delta power correlated with subjective dizziness and instability.

Conclusions

Neural resource demands of postural control increase with age, particularly in patients with UDE, driven by small vessel disease.

Significance

EEG correlates of postural control saturate in older adults with UDE, offering a neuro-physiological basis to this common syndrome.

Neurological update: dizziness

The diagnosis and management of vertigo remains a challenge for clinicians, including general neurology. In recent years there have been advances in the understanding of established vestibular syndromes, and the development of treatments for existing vestibular diagnoses. In this 'update' I will review how our understanding of previously "unexplained" dizziness in the elderly is changing, explore novel insights into the pathophysiology of vestibular migraine, and its relationship to the newly coined term 'persistent postural perceptual dizziness', and finally discuss how a simple bedside oculomotor assessment may help identify vestibular presentations of stroke.

Theoretical framework for "unexplained" dizziness in the elderly: The role of small vessel disease

In this paper we postulate that disruption of connectivity in the human brain can lead to dizziness, a symptom normally associated with focal disease of the vestibular system. The specific case that we will examine is the development of "unexplained" dizziness in the elderly-an extremely common clinical problem. Magnetic resonance imaging of the brain in the elderly usually show variable degrees of multifocal micro-angiopathy (small vessel white matter disease, SVD); thus, we review the literature, present a conceptual model and report preliminary quantitative EEG data in support of the hypothesis that such hemispheric SVD leads to central nervous system disconnection that elderly patients report as dizziness. Loss of connectivity by age-related build-up of SVD could lead to dizzy feelings through one or more of the following mechanisms: disconnection of cortical vestibular centers, disconnection between frontal gait centers and the basal ganglia, and disconnection between intended motor action (efference copy) and sensory re-afference. Finally, we propose that SVD-mediated dysregulation of cerebral blood pressure is linked to dizziness during standing and walking in elderly patients with "unexplained" dizziness.

Objective measures of gait and balance in healthy non-falling adults as a function of age

BACKGROUND

Neurodegenerative diseases increase in incidence with age. Prior studies using differing populations and gait paradigms have reported various parameters changing with age, some of which correlate with falls and mortality. Here we use three different paradigms to evaluate gait and balance in healthy non-fallers.

RESEARCH QUESTION

What objective gait and balance parameters are correlated with aging.

METHODS

Healthy subjects aged 21-79 years without histories of falls, lower extremity orthopedic procedures or chronic pain were included. Subjects walked on a 20 × 4 foot pressure sensor mat (Zeno Walkway, Protokinetics, Havertown, PA) under three different gait paradigms, (i) steady-state gait, (ii) dual-task while texting on a cellular phone and (iii) tandem gait. Data was collected and analyzed using PKMAS software (Protokinetics). Linear regression analysis, stepwise multivariate analysis, and grouped analysis of gait parameters was performed using SPSS 24 (IBM).

RESULTS

Seventy-five subjects were enrolled. Grouped analysis and linear regression analysis showed differing significance in parameters tested. Step-wise multivariate analysis of all 31 parameters assessed from three different gait paradigms, showed weak but significant correlations in age with (i) stride-to-stride variability in (i) integrated-pressure of footsteps and (ii) stride-length during steady-state gait, (iii) mean stride-length on dual-task, and (iv) mean step-width on tandem gait (R2 = 0.382, t = 2.26, p = 0.026).

SIGNIFICANCE

In a population of healthy subjects without prior history of falls or medical illness that should affect gait, there were weak but significant age-related changes in objective measures of steady state gait and balance. Future prospective longitudinal data will help predict the relevance of this in relation to falls in the elderly.

Age-Related Vestibular Loss: Current Understanding and Future Research Directions

The vestibular system sub-serves a number of reflex and perceptual functions, comprising the peripheral apparatus, the vestibular nerve, the brainstem and cerebellar processing circuits, the thalamic relays, and the vestibular cerebral cortical network. This system provides signals of self-motion, important for gaze and postural control, and signals of traveled distance, for spatial orientation, especially in the dark. Current evidence suggests that certain aspects of this multi-faceted system may deteriorate with age and sometimes with severe consequences, such as falls. Often the deterioration in vestibular functioning relates to how the signal is processed by brain circuits rather than an impairment in the sensory transduction process. We review current data concerning age-related changes in the vestibular system, and how this may be important for clinicians dealing with balance disorders.

Vestibular perception and the vestibulo-ocular reflex in young and older adults

OBJECTIVES

Quantification of the perceptual thresholds to vestibular stimuli may offer valuable complementary information to that provided by measures of the vestibulo-ocular reflex (VOR). Perceptual thresholds could be particularly important in evaluating some subjects, such as the elderly, who might have a greater potential of central as well as peripheral vestibular dysfunction. The authors hypothesized that perceptual detection and discrimination thresholds would worsen with aging, and that there would be a poor relation between thresholds and traditional measures of the angular VOR represented by gain and phase on rotational chair testing.

DESIGN

The authors compared the detection and discrimination thresholds of 19 younger and 16 older adults in response to earth-vertical, 0.5 Hz rotations. Perceptual results of the older subjects were then compared with the gain and phase of their VOR in response to earth-vertical rotations over the frequency range from 0.025 to 0.5 Hz.

RESULTS

Detection thresholds were found to be 0.69 ± 0.29 degree/sec (mean ± standard deviation) for the younger participants and 0.81 ± 0.42 degree/sec for older participants. Discrimination thresholds in younger and older adults were 4.83 ± 1.80 degree/sec and 4.33 ± 1.57 degree/sec, respectively. There was no difference in either measure between age groups. Perceptual thresholds were independent of the gain and phase of the VOR.

CONCLUSIONS

These results indicate that there is no inevitable loss of vestibular perception with aging. Elevated thresholds among the elderly are therefore suggestive of pathology rather than normal consequences of aging. Furthermore, perceptual thresholds offer additional insight, beyond that supplied by the VOR alone, into vestibular function.

White matter microstructural organization and gait stability in older adults

Understanding age-related decline in gait stability and the role of alterations in brain structure is crucial. Here, we studied the relationship between white matter microstructural organization using Diffusion Tensor Imaging (DTI) and advanced gait stability measures in 15 healthy young adults (range 18–30 years) and 25 healthy older adults (range 62–82 years). Among the different gait stability measures, only stride time and the maximum Lyapunov exponent (which quantifies how well participants are able to attenuate small perturbations) were found to decline with age. White matter microstructural organization (FA) was lower throughout the brain in older adults. We found a strong correlation between FA in the left anterior thalamic radiation and left corticospinal tract on the one hand, and step width and safety margin (indicative of how close participants are to falling over) on the other. These findings suggest that white matter FA in tracts connecting subcortical and prefrontal areas is associated with the implementation of an effective stabilization strategy during gait.

Workload influence on fatigue related psychological and physiological performance changes of aviators

OBJECTIVE

We evaluated a variety of non-invasive physiological technologies and a series of test approaches for examination of aviator performances under conditions of mental workload in order to provide a standard real-time test for physiological and psychological pilot fatigue assessments.

METHODS

Twenty-one male aviators were selected for a simulated flight in a hypobaric cabin with artificial altitude conditions of 2400 meter above sea level. The simulated flight lasted for 1.5 h, and was repeated for two times with an intervening 0.5 h rest period outside the hypobaric cabin. Subjective criteria (a fatigue assessment instrument [FAI]) and objective criteria (a standing-position balance test as well as a critical flicker fusion frequency (CFF) test) were used for fatigue evaluations.

RESULTS

No significant change was observed in the FAI scores before and after the simulated flight, indicating that there was no subjective fatigue feeling among the participants. However, significant differences were observed in the standing-position balance and CFF tests among the subjects, suggesting that psychophysiological indexes can reflect mental changes caused by workload to a certain extent. The CFF test was the simplest and clearly indicated the occurrence of workload influences on pilot performances after a simulated flight.

CONCLUSIONS

Results showed that the CFF test was the easiest way to detect workload caused mental changes after a simulated flight in a hypobaric cabin and reflected the psychophysiological state of aviators. We suggest that this test might be used as an effective routine method for evaluating the workload influences on mental conditions of aviators.

Motor Activity in Aging: An Integrated Approach for Better Quality of Life

Old age is normally associated with stereotypical structural and physiological changes in the brain that are caused by deterioration in elementary cognitive, sensory, and sensorimotor functions as well as increased susceptibility to stress. These changes are connected with gait impairment and falls, especially among patients with common neurological diseases. Even in the absence of history of falling or when there is no physical injury after a fall, many older people develop a fear of falling that leads to restricted mobility, reduced activity, depression, social isolation, worsened metabolic disease, and increasing risk of cardiovascular morbidity and mortality. Although links between cognitive decline and age-associated brain changes have been clarified, relationships between gait disorders and psychophysiological alterations in aging are less well understood. This review focuses on two crucial elements of aged individuals with gait disorders: characteristic comorbidities in the elderly and the psychophysiological effects of physical exercise in the elderly with gait disorder. We propose an integrated approach to studying elderly subjects with gait disorder before starting a program of motor rehabilitation with wearable robotic devices, in order to investigate the effectiveness and safety of the ambulatory training.

Characterization of presbyequilibrium among institutionalized elderly persons

OBJECTIVE

The aim was to characterize dizziness, vertigo, poor maintenance of posture, and sudden instabilities (called presbyequilibrium) among institutionalized elderly to model and identify possible treatable causes.

METHODS

A questionnaire based study focusing on symptoms among 72 elderly persons from a single residential facility and followed them for 3 years.

RESULTS

Dizziness, vertigo, poor maintenance of posture, and black-outs were reported by 68% of the 72 elderly and make them at risk for falls, and reduced quality of life. The most common complaint was postural instability, with a tendency to fall. "Spinning" vertigo and "floating" sensation had a strong inter-correlation and correlated with habitual falls. The various dizziness symptoms often occurred in combinations. Attacks of self-experienced syncope never occurred alone but always in combination with "spinning vertigo" or "tendency to fall". In factorial analysis, presbyequilibrium could be divided into six categories. Two of these categories correlated with falls.

CONCLUSIONS

Among elderly, presbyequilibrium is commonly characterized by a combination of phenomena involving perceptual, orientation, postural, and autonomic manifestations. It is often difficult to obtain an accurate history from the elderly and the presence of vestibular symptoms is frequently overlooked. Taking a careful history and utilizing the classification of symptoms that emerged from the factorial analysis may give a deeper understanding of the etiology of presbyequilibrium, thereby facilitating appropriate rehabilitation.

Balance and gait problems in the elderly

Gait and balance problems are common with advancing age. Disorders of balance and gait are particularly important in the elderly because they compromise independence and contribute to the risk of falls and injury. Although they are considered as separate clinical entities, balance and gait disturbance are often intertwined. Here, we discuss the principal anatomical and physiologic mechanisms responsible for balance and gait. We also review the different types of fall patterns commonly seen in subjects and a classification scheme for various gait disorders. Furthermore, we consider the relationship between balance and gait disorders and subcortical vascular disease. Potential interventions and therapies in those individuals with balance and gait disorders are also discussed.

Predictors of postural stability in children with ADHD

OBJECTIVE

As children with ADHD who have more inattention problems are more frequently with fine motor problems, it is not clear whether postural balance problems are associated with different subtypes of ADHD. This study investigates the predictors of postural stability in children with ADHD considering the covariant factors of age, gender, and comorbidities.

METHOD

A total of 103 children with ADHD are studied using Poor Postural Stability Questionnaire filled out by their parents.

RESULTS

Linear regression analysis indicates that only oppositional-defiant behavior score is the predictor of seeking-movement subscale score. ADHD type does not predict the score of avoiding-postural-instability subscale, whereas separation anxiety score did so.

CONCLUSION

ADHD subtypes do not have distinct clinical profiles of the balance problems. Postural stability in children with ADHD depends on the comorbid psychiatric disorders rather than ADHD subtypes.

White matter fractional anisotropy predicts balance performance in older adults

Aging is characterized by brain structural changes that may compromise motor functions. In the context of postural control, white matter integrity is crucial for the efficient transfer of visual, proprioceptive and vestibular feedback in the brain. To determine the role of age-related white matter decline as a function of the sensory feedback necessary to correct posture, we acquired diffusion weighted images in young and old subjects. A force platform was used to measure changes in body posture under conditions of compromised proprioceptive and/or visual feedback. In the young group, no significant brain structure-balance relations were found. In the elderly however, the integrity of a cluster in the frontal forceps explained 21% of the variance in postural control when proprioceptive information was compromised. Additionally, when only the vestibular system supplied reliable information, the occipital forceps was the best predictor of balance performance (42%). Age-related white matter decline may thus be predictive of balance performance in the elderly when sensory systems start to degrade.

Gait disorders of unknown cause in the elderly: Clinical and MRI findings

BACKGROUND

Disequilibrium of unknown cause in older people has been associated with white matter lesions on neuroimaging studies.

OBJECTIVE

To investigate the relationship between gait and balance problems in the elderly, white matter hyperintensities, and vascular risk factors.

METHODS

We studied clinical and neuroimaging features in 30 people older than 65 years of age with gait disorders of unknown cause and 30 age- and sex-matched controls. Patients and controls underwent the same extensive quantitative test battery. White matter lesions on MRI scans were graded in different brain regions.

RESULTS

History of hypertension was more common among patients than controls (60% vs. 27%, p=0.012). On all scales, patients with gait disorders scored worse than controls. The frequency of white matter lesions was significantly higher in patients than in controls (p<0.001). In a multivariate logistic regression analysis in which diagnosis (patient vs. control) was the dependent variable, there was an association between diagnosis and white matter signal hyperintensity score (p<0.001) and history of hypertension (p=0.039).

CONCLUSIONS

Gait disorders of unknown cause in older people are associated both with white matter lesions on MRI scans and with history of hypertension.

Higher level gait disorders

Higher level gait disorders are common in the elderly. The pathophysiology of these gait disorders is poorly understood, and the nomenclature used to describe them is confusing and the subject of ongoing debate. It is suggested that higher level gait disorders can be explained in terms of breakdown in the organization of equilibrium and locomotion.

Higher level gait disorders

This short review is derived from the contributions of the authors at a meeting on gait disorders and higher mental function held in Madrid in February 2006 and is submitted at the request of the meeting convenor, Dr N Giladi.

Neurological gait disorders in elderly people: clinical approach and classification

Gait disorders are common and often devastating companions of ageing, leading to reductions in quality of life and increased mortality. Here, we present a clinically oriented approach to neurological gait disorders in the elderly population. We also draw attention to several exciting scientific developments in this specialty. Our first focus is on the complex and typically multifactorial pathophysiology underlying geriatric gait disorders. An important new insight is the recognition of gait as a complex higher order form of motor behaviour, with prominent and varied effects of mental processes. Another relevant message is that gait disorders are not an unpreventable consequence of ageing, but implicate the presence of underlying diseases that warrant specific diagnostic tests. We next discuss the core clinical features of common geriatric gait disorders and review some bedside tests to assess gait and balance. We conclude by proposing a practical three-step approach to categorise gait disorders and we present a simplified classification system based on clinical signs and symptoms.

Postural control after a night without sleep

The present study analysed the efficiency of postural control after 12 h of nocturnal forced wakefulness using Romberg's test comprising 1 min of recording with eyes-open and 1 min of recording with eyes-closed, with a 1 min break between the two sessions. Our aim was to see if the decreased postural control efficiency after a sleepless night was unspecific (in both eyes-closed and eyes-open conditions) or selective (in only one of the conditions). A total of 55 students spent a whole night awake at our laboratory and were tested at 22:00 and 08:00 h. In general, the results showed that postural sway increased, performing the recording from eyes-open to eyes-closed condition. The statokinesigram length (SL or efficiency of the postural system) increased after the sleepless night, while in eyes-open condition, the length in function of surface (LFS or accuracy of postural control) and Romberg's index (or contribution of vision to maintain posture) significantly decreased. This could indicate that after a night without sleep, there is a slower elaboration of visual inputs in the postural control process. On the basis of these results, the effects of sleep deprivation on cognitive performance were considered from a neuropsychological point of view.

The meaning of distal sensory loss and absent ankle reflexes in relation to age

CONTEXT

Polyneuropathy is a common disease and is more prevalent (at least 3 %) in elderly people. However, routine neurological examination of healthy elderly people may show distal sensory loss and absent tendon reflexes, which can obscure the distinction from polyneuropathy.

OBJECTIVE

To investigate the relation between age and the prevalence of distal sensory loss, absent tendon reflexes, or muscle weakness, and to ascertain above which age these neurological signs could be considered as normal in ageing.

DATA SOURCES

PubMed, Embase, the Cochrane Library, and Current Contents from 1960 until 2004. Reference lists of relevant studies were searched for additional studies, reviews or textbooks.

STUDY SELECTION

Studies reporting on neurological signs upon routine neurological examination in generally healthy adult persons were considered for inclusion. Two reviewers independently assessed study eligibility and performed study inclusion. Of 629 studies initially identified, 50 (8 %) met the inclusion criteria.

DATA EXTRACTION

Two reviewers independently performed data extraction and assessed study quality based on study design and the rigour by which confounding co-morbidity was excluded.

DATA SYNTHESIS

The 50 included studies comprised a total of 9,996 adult persons. Assuming heterogeneity between studies, the prevalence data from different studies were pooled for separate age groups with a random-effects model. In healthy persons older than 60 years the prevalence of absent vibration sense at the big toes (29 % [95 % CI 18 % to 38%]) or ankles (15 % [95 % CI 11 % to 20%]), and absent ankle reflexes (23 % [95 % CI 16 % to 30 %]) was increased.

CONCLUSIONS

Self-declared healthy adult persons younger than 60 years do not have neurological signs. After the age of 60 absent vibration sense at the big toes or ankles, and absent ankle reflexes are more prevalent, although the majority does not have these neurological signs. It seems more appropriate to apply different diagnostic criteria for polyneuropathy in adult persons younger and older than 60 years.

Antiepileptic drugs and their impact on balance

Antiepileptic drugs (AEDs) are being used with increasing frequency, not only to manage epilepsy, but also in the treatment of other conditions including neuropathic pain, migraine headaches and psychiatric conditions requiring mood stabilization. Although AEDs as a class are commonly prescribed in older patients and those with a predisposition to imbalance, the effect these drugs exert on gait and equilibrium has received very little study. Data from controlled efficacy and safety trials suggests that some AEDs are more apt to affect balance than others, even at therapeutic doses. In particular, phenytoin, primidone and phenobarbital produce more dizziness than some of the newer AEDs such as lamotrigine, levetiracetam and oxcarbazepine. For some of the other new AEDs, the data are simply not sufficient to estimate their effect on balance. This article reviews the current evidence that may guide the clinician in choosing a medication likely to have a low impact on gait and balance. Considering the risks and morbidity associated with imbalance and falls, particularly in the elderly, the direct effects of AEDs on balance should be examined further.

Clinical characteristics of elderly patients with a cautious gait of unknown origin

OBJECTIVE

To evaluate and systematically characterize a group of older adults with disturbed gait of unknown origin.

DESIGN

Cross-sectional study.

SETTING

Outpatient clinic in a movement disorders unit.

PARTICIPANTS

Twenty-five patients (mean age 78.4 years) with a disturbed gait of unknown origin were compared with twenty-eight age matched "healthy" controls (mean age 78.2).

MEASUREMENT

Detailed medical history, geriatric and neurological assessments.

RESULTS

Patients walked more slowly (P<0.0001) and with shorter strides (P<0.0001) compared with controls. Muscle strength was lower, and static and dynamic balance and gait performance were worse among the patients (P<0.0001). The patients also tended to be more depressed (P<0.0001),more anxious (P<0.002), had a greater fear of falling (P<0.0001) and had lower scores on the Mini-Mental State Examination (P<0.005). There was no difference in the frequency of cerebellar or pyramidal signs in the two groups. However, neurological testing revealed that extrapyramidal (P<0.0001) and frontal release signs (P<0.0001) were more common among the patients. Neuroradiological findings were rare among the patients and they did not explain the changes in gait speed or fear of falling.

CONCLUSIONS

Older adults with a disturbed gait of unknown origin appear to share common characteristics. They walk more slowly than "healthy" controls with increased unsteadiness and with excessive fear of falling. The extrapyramidal, frontal lobe, and limbic systems apparently play an important role, to different degrees, in what can be viewed as a multisystem neurodegenerative syndrome clearly different from "aging."

Falls and vestibular impairment

Unexplained fall is one of the commonest presentations to the Accident and Emergency (A & E) department of a hospital. The objective of this study is to assess the proportion of patients with symptoms of vestibular impairment among those presenting to an A & E department with an unexplained fall. Out of the total 3139 patients (fallers) presenting to an A & E department in 6 months, 546 had no known cause for the fall. Of these, 428 (76%) completed the vestibular symptom scale questionnaire. The presence and severity of vestibular symptoms for the past 12 months were assessed. The results showed that 80% of these patients had symptoms of vestibular impairment. We conclude that a large proportion of unexplained fallers suffered from symptoms of vestibular impairment within the last year, which may be responsible for their imbalance and falls. Identifying this group of patients is important as their symptoms and the resultant postural instability can be ameliorated by vestibular rehabilitation exercises.

Age-dependent variations in the directional sensitivity of balance corrections and compensatory arm movements in man

We investigated the effects of ageing on balance corrections induced by sudden stance perturbations in different directions. Effects were examined in biomechanical and electromyographic (EMG) recordings from a total of 36 healthy subjects divided equally into three age groups (20-34, 35-55 and 60-75 years old). Perturbations consisted of six combinations of support-surface roll (laterally) and pitch (forward-backward) each with 7.5 deg amplitude (2 pure pitch, and 4 roll and pitch) delivered randomly. To reduce stimulus predictability further and to investigate scaling effects, perturbations were at either 30 or 60 deg s(-1). In the legs, trunk and arms we observed age-related changes in balance corrections. The changes that appeared in the lower leg responses included smaller stretch reflexes in soleus and larger reflexes in tibialis anterior of the elderly compared with the young. For all perturbation directions, onsets of balance correcting responses in these ankle muscles were delayed by 20-30 ms and initially had smaller amplitudes (between 120-220 ms) in the elderly. This reduced early activity was compensated by increased lower leg activity after 240 ms. These EMG changes were paralleled by comparable differences in ankle torque responses, which were initially (after 160 ms) smaller in the elderly, but subsequently greater (after 280 ms). Findings in the middle-aged group were generally intermediate between the young and the elderly groups. Comparable results were obtained for the two different stimulus velocities. Stimulus-induced trunk roll, but not trunk pitch, changed dramatically with increasing age. Young subjects responded with early large roll movements of the trunk in the opposite direction to platform roll. A similarly directed but reduced amplitude of trunk roll was observed in the middle-aged. The elderly had very little initial roll modulation and also had smaller stretch reflexes in paraspinals. Balance-correcting responses (over 120-220 ms) in gluteus medius and paraspinals were equally well tuned to roll in the elderly, as in the young, but were reduced in amplitude. Onset latencies were delayed with age in gluteus medius muscles. Following the onset of trunk and hip balance corrections, trunk roll was in the same direction as support-surface motion for all age groups and resulted in overall trunk roll towards the fall side in the elderly, but not in the young. Protective arm movements also changed with age. Initial arm roll movements were largest in the young, smaller in the middle aged, and smallest in the elderly. Initial arm roll movements were in the same direction as initial trunk motion in the young and middle aged. Thus initial roll arm movements in the elderly were directed oppositely to those in the young. Initial pitch motion of the arms was similar across age groups. Subsequent arm movements were related to the amplitude of deltoid muscle responses which commenced at 100 ms in the young and 20-30 ms later in the elderly. These deltoid muscle responses preceded additional arm roll motion which left the arms directed 'downhill' (in the direction of the fall) in the elderly, but 'uphill' (to counterbalance motion of the pelvis) in the young. We conclude that increased trunk roll stiffness is a key biomechanical change with age. This interferes with early compensatory trunk movements and leads to trunk displacements in the direction of the impending fall. The reversal of protective arm movements in the elderly may reflect an adaptive strategy to cushion the fall. The uniform delay and amplitude reduction of balance-correcting responses across many segments (legs, hips and arms) suggests a neurally based alteration in processing times and response modulation with age. Interestingly, the elderly compensated for these 'early abnormalities' with enlarged later responses in the legs, but no similar adaptation was noted in the arms and trunk. These changes with age provide an insight into possible mechanisms underlying falls in the elderly.

Gait disorders

BACKGROUND

Disorders of gait and mobility are common neurologic abnormalities of aging and can have disastrous consequences. Etiology is multifactorial, and normal age-related changes are difficult to distinguish from those resulting from the disease.

REVIEW SUMMARY

Gait evaluation with special techniques provides scientific understanding of physiologic mechanisms, but experienced clinicians can make diagnoses based on general medical and neurologic history and physical examination. Details to observe include posture, length of stride, width of base, speed and fluidity of motion, arm swing, bilateral symmetry of motor activity, and neurologic signs. Gait disorders are classified into lowest-level, middle-level, and highest-level disorders. In lowest-level gait disorders, only one major afferent system (visual, proprioceptive, or vestibular) is affected and the disturbance is usually self-limited or compensated. Middle-level disorders include myelopathy from cervical spondylosis; spastic hemiparetic gait from unilateral impairment of the corticospinal tract; gaits associated with movement disorders; and dystonic, choreic, hemiballistic, and cerebellar ataxic gaits. Highest-level gait disorders include cautious gait, subcortical dysequilibrium, frontal dysequilibrium, isolated gait ignition failure, frontal gait, primary progressive freezing gait, and psychogenic gait disorders.

CONCLUSIONS

A treatable cause can often be found. Physical therapy with gait evaluation and training is recommended. Medication must be kept to a minimum.

Vestibulocollic reflexes: normal values and the effect of age

OBJECTIVES

To define normal values and examine the influence of ageing on vestibulocollic reflexes (VCR).

METHODS

Vestibulocollic responses to 100 dB (normal hearing level; NHL) clicks, forehead taps and galvanic stimulation were measured in 70 healthy adults aged 25-85 years.

RESULTS

Click- and galvanic-evoked responses were present bilaterally in all subjects below 60. Average click-evoked response amplitudes decreased with age, with a pronounced decline of 25-30% per decade from the 6th decade. The average click thresholds increased from 85 dB in the third decade to 96.5 dB in the 8th and 9th decades. Average galvanic-evoked VCR amplitudes decreased sharply from the seventh decade. Tap-evoked reflex amplitudes showed a milder decrease. When side to side differences in amplitude were expressed as asymmetry ratios (AR) in subjects below the age of 60, values of up to 35 and 46% were obtained for click amplitudes corrected and uncorrected for background electromyogram (EMG), up to 61% for both corrected and uncorrected tap response amplitudes, and up to 41 and 55% for corrected and uncorrected galvanic-evoked responses.

CONCLUSIONS

A normative range of values can be specified for click- and galvanic-evoked VCRs for subjects up to the age of 60. Click- and galvanic-evoked VCR amplitudes decrease rapidly thereafter while tap-evoked responses are less affected. These changes are probably due to morphological changes in the vestibular system occurring with ageing and are more marked than in several previous reports of age-related changes in caloric responses and vestibulo-ocular reflexes.

What can posturography tell us about vestibular function?

Patients with balance disorders want answers to the following basic questions: (1) What is causing my problem? and (2) What can be done about my problem? Information to fully answer these questions must include status of both sensory and motor components of the balance control systems. Computerized dynamic posturography (CDP) provides quantitative assessment of both sensory and motor components of postural control along with how the sensory inputs to the brain interact. This paper reviews the scientific basis and clinical applications of CDP. Specifically, studies describing the integration of vestibular inputs with other sensory systems for postural control are briefly summarized. Clinical applications, including assessment, rehabilitation, and management are presented. Effects of aging on postural control along with prevention and management strategies are discussed.

Neurologic disorders of gait

Gait disorders are important because of their prevalence, particularly among the elderly, and the associated risk of falls and injury. Neural networks that organize locomotion and maintain balance are briefly reviewed. Gait disorders can be classified based on observational features or by etiology. Several common disorders are discussed in more detail. Recent progress includes use of botulinum toxin for spastic gait in cerebral palsy, neurosurgical treatment of Parkinson's disease, and newer rehabilitation approaches to gait and balance training.

Equilibrium and Balance in the Elderly

Complaints of dizziness and disequilibrium increase with age. Sixty-five percent of individuals older than 60 years of age experience dizziness or loss of balance, often on a daily basis.

Some degree of imbalance is present in all individuals older than 60. This is the result of a generalized functional degradation. Initially, the imbalance is situational and manifests when the righting reflexes cannot meet the demands of a challenging environment, such as a slippery surface. As the functional degradation progresses, the imbalance occurs during everyday activities, independent ambulation becomes difficult, and the likelihood of falls increases. When instability is constant, the individual resorts to the use of a cane, a walker, or a wheelchair.

Equilibrium and limb coordination in mild cognitive impairment and mild Alzheimer's disease

OBJECTIVE

To examine changes in equilibrium and limb coordination in normal aging, mild cognitive impairment, and moderate cognitive impairment associated with early probable Alzheimer's disease (AD), by means of parametric clinical measures.

DESIGN

Case series

SETTING

Out-patient clinic.

PARTICIPANTS

A consecutive sample of 365 community-residing ambulatory volunteers (137 men, 228 women; mean age 70.4 +/- 9.4 years; mean educational attainment 14.6 +/- 3.1 years), who were followed in an ongoing longitudinal study of aging and AD, comprising cognitively intact individuals, persons with mild cognitive impairment, and patients with mild AD.

MEASUREMENTS

For general magnitude of cognitive function, the Global Deterioration Scale (GDS). For cognition, the Mini-Mental State Examination (MMSE). Equilibrium was assessed with parametric measurements of single leg stance (SLS) and tandem walking (TW). Limb coordination was assessed with parametric measurements of foot tapping (FT), alternating pronation and supination (PS), and sequential finger to thumb tapping (FTH).

MAIN RESULTS

After adjustment for age, persons with mild cognitive impairment or mild AD had significantly poorer performance on parametric clinical tests of equilibrium and limb coordination compared with cognitively intact individuals (P < .05).

CONCLUSIONS

Changes in equilibrium and limb coordination are clinically demonstrable in persons with mild cognitive impairment and mild AD using simple parametric tests. Such tests could potentially identify individuals with increased risk of falling. Early diagnosis and treatment of conditions that can jeopardize equilibrium and limb coordination, as well as balance and coordination training, might help cognitively impaired older people to maintain optimal function and may decrease the risk of falls and injuries.

Brain activation during maintenance of standing postures in humans

The regulatory mechanism of bipedal standing in humans remains to be elucidated. We investigated neural substrates for maintaining standing postures in humans using PET with our mobile gantry PET system. Normal volunteers were instructed to adopt several postures: supine with eyes open toward a target; standing with feet together and eyes open or eyes closed; and standing on one foot or with two feet in a tandem relationship with eyes open toward the target. Compared with the supine posture, standing with feet together activated the cerebellar anterior lobe and the right visual cortex (Brodmann area 18/19), and standing on one foot increased cerebral blood flow in the cerebellar anterior vermis and the posterior lobe lateral cortex ipsilateral to the weight-bearing side. Standing in tandem was accompanied by activation within the visual association cortex, the anterior and posterior vermis as well as within the midbrain. Standing with eyes closed activated the prefrontal cortex (Brodmann area 8/9). Our findings confirmed that the cerebellar vermis efferent system plays an important role in maintenance of standing posture and suggested that the visual association cortex may subserve regulating postural equilibrium while standing.

Idiopathic Bilateral Vestibular Loss

We describe the clinical and laboratory features of 13 patients with bilateral loss of peripheral vestibular sensitivity of no known cause. In the office, screening for this condition was possible using illegible e-testing and examination of the patient for refixation saccades after brisk head movements while attempting visual fixation. Diagnosis was confirmed by bilaterally reduced caloric responses (<20 degrees/second on all 4 caloric irrigations) and abnormally low gain of the vestibulo-ocular reflex on rotational chair testing. The mean age of the patients was 68 years. We noted two patterns of symptom onset: onset associated with vertigo (10 patients) and insidious progressive disequilibrium not associated with vertigo (3 patients). Only 38 % of the patients complained of subjective oscillopsia. The subjects performed poorly on platform posturography, particularly when deprived of visual and somatosensory feedback. When associated with vertigo, bilateral vestibular loss may be the result of bilateral sequential vestibular neuritis; when not associated with vertigo, disequilibrium may be caused by slow, symmetrical loss of peripheral function as a result of aging. Although the subjects in this report were elderly, idiopathic bilateral vestibular loss has been reported in patients of all ages.

"Subclinical" orthostatic hypotension is associated with dizziness in elderly patients with Parkinson disease

OBJECTIVE

To investigate risk factors associated with subjective complaints of dizziness in 12 elderly patients with Parkinson disease (PD), in whom no obvious cause for this symptom could be found.

DESIGN

A case-controlled study, with patients prospectively recruited in a nonblinded fashion.

SETTING

Patients were seen by one physician at a neurology outpatient clinic between August 1993 and August 1994.

SUBJECTS

Thirty-six patients, all over age 65 years and all with PD; 12 complained of dizziness; 24 did not.

INTERVENTIONS

Patients and controls were screened for blood pressure changes, postural instability, motor severity, multiple sensory deficits, drug use, cardiovascular disease, and diabetes mellitus.

MAIN OUTCOME MEASURES

An orthostatic decrease of systolic BP > 15 mmHg (odds ratio = 6.5; 95% confidence interval = 1.22 - 34.52; chi 2mh = 6.7; p < .01) and an orthostatic decrease of diastolic BP > 5mmHg (odds ratio = 11; 95% confidence interval = 3.15 - 38.39; chi 2mh = 7.14; p < .01) were significant risk factors for complaints of dizziness.

RESULTS

The only significant risk factors linked with dizziness were orthostatic decreases in systolic (15 mmHg) and diastolic (5 mmHg) blood pressure.

CONCLUSIONS

An orthostatic decrease in blood pressure is associated with unexplained feelings of dizziness in elderly PD patients.

The relationship of postural sway to sensorimotor function, functional performance, and disability in the elderly

OBJECTIVE

To examine the relationship of postural sway to sensorimotor impairment, functional performance, and self-reported disability.

DESIGN

Cross-sectional cohort.

SETTING

Department of Veterans' Affairs Medical Center.

PATIENTS

One hundred community-dwelling elderly unable to climb stairs step over step.

MAIN OUTCOME MEASURES

Postural sway (area of ellipse and path length, eyes open and closed), sensorimotor (strength, sensation, range of motion, central processing time), functional performance (functional reach, timed gait, mobility skills, endurance), and disability (MOS-SF36, Falls Efficacy Scale [FES]).

RESULTS

Postural sway area measures correlated with sensorimotor measures: (1) During eyes-closed conditions, increased sway occurs in individuals with sensory deficits (p < .05); (2) Sway was positively correlated with tibialis anterior latency (p < .05); (3) Sway area measures increased with increased strength (p < .05). The sway/strength relationship may be explained by week subjects improving their stability by limiting rather than increasing sway. Sway was not significantly correlated with any measures of physical performance. Sway was correlated with some measures of disability: (1) Eyes-closed measures of postural sway were correlated with FES scores (p < .05); (2) Sway was not correlated with the MOS-36 physical functioning question. When controlling for functional measures, eyes-closed measures of sway significantly predicted FES scores (p < .03).

CONCLUSIONS

Measures of postural sway are more likely capturing sensorimotor deficits rather than differentiating functional performance abilities, and the relationship between postural sway and self-reported disability is inconsistent.

Neurotology

As in most areas of clinical medicine, the history often is the key to determining the diagnosis in patients presenting with neurotologic symptoms. The most common cause of vertigo--benign positional vertigo--can be diagnosed at the bedside based on the characteristic history and the finding of fatigable positional nystagmus on the Dix-Hallpike positional test. Furthermore, it can be cured with a simple positioning maneuver. Quantitative auditory and vestibular function tests are important for documenting the site and severity of deficit in patients with chronic neurotologic symptoms. Only a few presentations (listed in section on acute vertigo) require immediate neuroimaging.

Posturography and balance problems in older people

OBJECTIVE

To determine which measurements and test conditions on posturography are most useful for identifying balance problems in older people.

SUBJECTS

Two samples of 70 community-dwelling older subjects (> 75 years). One group (controls) considered their balance normal for their age, and the other (patients) complained of imbalance.

MEASUREMENTS

Velocity of sway on static (with and without foam) and dynamic posturography, Tinetti gait and balance score, self-reported fear of falling, and number and circumstances of falls.

RESULTS

Mean sway velocity was significantly increased in patients compared with controls. The greatest difference between patients and controls occurred with measures of anterior-posterior sway velocity during angular tilt of the platform. Sway velocity was not significantly increased in patients or controls who reported falls compared with those who did not report falls. Even when comparing those who fell as a result of loss of balance with those who fell because of trips or slips, there was no significant difference in sway velocity. By contrast, those who reported fear of falling (patients and controls) had significantly increased sway velocity compared with those who did not report fear of falling.

CONCLUSION

On average, velocity of sway (particularly in the anterior-posterior direction) is higher in older subjects who complain of imbalance compared with age-matched controls, and the difference is greater with dynamic posturography than with static posturography. However, the posturography data provided little information about the cause of the imbalance and did not correlate with the frequency of reported falls.

Biomechanical assessment of quiet standing and changes associated with aging

The kinematics of standing balance were analyzed in 24 normal subjects, aged 21 to 78 years, to examine differences attributable to age, visual input, and sex. Movements of individual body segments, displacement of the center of gravity (COG), and position of the center of pressure (COP) were measured, and total path length and variability about the mean position were derived from the resulting values. Aging was associated with an increase in variability of the COG, head, and hip, but not in path length. The changes, which may be clinically interpreted as excess postural sway, do not show stability deficits as a consequence of aging. On the contrary, older subjects seem to adopt a postural control strategy that achieves comparable stability during quiet standing. Eye closure increased the anterior-posterior COP path length without corresponding changes in the COG, indicating an increase in small accelerations without associated instability. There was more medial-lateral movement in women than in men. Quantitative electromyographic measures showed that, in general, quiet standing requires very little muscular activity. We conclude that the task of quiet standing produces no evidence of postural instability concurrent with aging. The altered postural control strategy may be less effective when balance is suddenly or severely compromised.

Genetic factors in the etiology of idiopathic Parkinson's disease

Overshadowed by a vigorous search for an environmentally-derived toxin that would be possibly relevant for the pathogenesis of idiopathic Parkinson's disease (PD), genetic factors have largely been neglected for this condition during the last two decades. Recent descriptions of kindreds over three or more generations with several family members affected have renewed the interest in genetics of PD. Concurring with this, diagnostic concepts and pathologic criteria for PD and for idiopathic Lewy-body (LB) disease have been reevaluated such that LB-proven parkinsonism is sufficiently differentiated from familial parkinsonism without LB pathology. Surveys on genetic epidemiology in PD have confirmed the 19th century's notion that 10 to 15% of PD index cases report a further family member with PD. These figures were, however, substantiated on a statistical basis only in single surveys when comparisons were made with the numbers of PD relatives in control index cases. Twin studies did not reveal a higher rate of concordance within monozygotic pairs than in dizygotic pairs. Tests of striatal 18-F-Dopa uptake in clinically unaffected mono- and dizygotic co-twins did not alter the ratio between the concordance rates. Though not excluded by the twin studies, multifactorial (or polygenic) inheritance as well as mitochondrial inheritance are at present less likely to cover most of the inheritance pattern in familial LB parkinsonism. Instead, autosomal dominant inheritance with reduced penetrance is the most probable inheritance pattern for most of the reported pedigrees. Molecular genetic investigations have to consider the biochemical basis of the age- and region-specific pathology of PD. The first analyses of linkage and allelic associations gave inconclusive results in sporadic and familial PD. The hunt for metabolic factors that link geno- and phenotype expression in PD will continue.