Increased Body Sway Research Articles

Physiological factors associated with injurious falls in older people living in the community.

Performance in six tests of sensorimotor function was measured in 50 subjects who were admitted to an acute hospital because of a fall (ICD codes E880-888), but who did not suffer a fracture of the lower limbs as a result. Performances in these tests were compared with 50 subjects of the same age and sex who had not fallen in the previous 12 months. It was found that those admitted to hospital because of a fall had decreased tactile sensation, reduced quadriceps strength and increased body sway on firm and compliant surfaces. The fallers also performed poorly in clinical tests of static and dynamic balance. Psychoactive-drug use was associated with falling and a number of test measures, including body sway, static balance, dynamic balance and quadriceps strength. Twenty-seven percent of fallers had poor outcomes, in that 1 year after testing, they had either suffered three or more additional falls, been readmitted to hospital, been transferred to nursing homes or died.

Effect of dexmedetomidine and midazolam on human performance and mood

The effects of dexmedetomidine (DXM), a novel alpha 2-adrenoceptor agonist, on human performance and mood were studied in a double-blind randomized crossover study in 12 healthy student volunteers. Single IM doses of dexmedetomidine, 0.6 microgram/kg (DXM1) and 1.2 micrograms/kg (DXM2), 80 micrograms/kg midazolam (MID) and saline placebo, were given at one-week intervals. Performance was measured objectively and mood was assessed subjectively with visual analogue scales (VAS) at baseline and 40 min, 2 h, 4 h and 6 h after each injection. Blood pressure and heart rate in the sitting position were measured and venous blood was sampled during each testing round. DXM1 did not significantly impair cognitive (digit symbol substitution), coordinative (tracking) or reactive skills, and at 6 h it shortened reaction time and reduced errors in complex tracking. It produced exophoria, increased body sway with the eyes open and impaired subjective performance on VAS. The higher dose dexmedetomidine also caused impaired cognitive, coordinative and reactive skills (although a trend towards improved coordination was found at 6 h), reduced attention, produced exophoria, increased body sway with the eyes open and caused drowsiness, clumsiness, passiveness and mental slowness on the appropriate VAS scales. MID resembled DXM2 in impaired objective and subjective measures of skilled performance, although the objective effects of MID were of speedier onset and shorter duration. In contrast to MID, DXM caused a significant and dose-dependent decrease in systolic and diastolic blood pressure still detectable 6 h after injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical Pharmacology of Lamotrigine

The pharmacokinetics and pharmacodynamics of lamotrigine (LTG), a new antiepileptic drug (AED), were studied in healthy volunteers. In an open dose-escalating study, LTG 240 mg produced peak plasma concentrations of around 3 micrograms/mg with no significant adverse events. Subsequent pharmacokinetic studies revealed complete oral absorption, first-order kinetics with a mean half-life of approximately 1 day, and elimination mainly as a glucuronide in the urine. Early studies in patients with epilepsy revealed more rapid metabolism when given with enzyme-inducing AEDs and delayed metabolism by valproate. A placebo-controlled, double-blind study compared LTG 120 and 240 mg with phenytoin (PHT) 500 and 1,000 mg, and diazepam (DZP) 10 mg. Visual analogue scales showed sedation after PHT 1,000 mg and DZP 10 mg, but not after LTG. Smooth pursuit eye movements and adaptive tracking were impaired by DZP and PHT 1,000 mg. LTG did not affect these variables. A comparison of LTG 150 and 300 mg and carbamazepine (CBZ) 200, 400, and 600 mg demonstrated impairment of smooth pursuit and saccadic eye movements by CBZ 600 and 400 mg, but not by LTG. Additionally, CBZ 600 mg impaired adaptive tracking and increased body sway and heart rate. These studies have shown LTG to have desirable and predictable pharmacokinetic properties for an AED. Pharmacodynamic effects were absent, suggesting a high therapeutic index.

Postural Stability and Associated Physiological Factors in a Population of Aged Persons

A battery of 13 visual, vestibular, sensorimotor, and balance tests was administered to 95 elderly persons (mean age 82.7 years) to examine the relationships between specific sensorimotor functions and measures of postural stability. When subjects stood on a firm surface, increased body sway was associated with poor tactile sensitivity and poor joint position sense. When subjects stood on a compliant surface (which reduced peripheral sensation) with their eyes open, increased body sway was associated with poor visual acuity and contrast sensitivity, reduced vibration sense, and decreased ankle dorsiflexion strength as well as reduced joint position sense. Increased body sway with eyes closed on the compliant surface was associated with poor tactile sensation, reduced quadriceps and ankle dorsiflexion strength, and increased reaction time. Poor performance in two clinical measures of postural stability was associated with reduced sensation in the lower limbs as measured by joint position sense, tactile sensitivity and vibration sense, reduced quadriceps and ankle dorsiflexion strength, and slow reaction times. The prevalence of vestibular impairments was high in this group, but vestibular function was not significantly associated with sway under any of the test conditions. The results suggest that reduced sensation, muscle weakness in the legs, and increased reaction time are all important factors associated with postural instability. An analysis of the percentage increases in sway under conditions where visual and peripheral sensation systems are removed or diminished, compared with sway under optimal conditions, indicated that peripheral sensation is the most important sensory system in the maintenance of static postural stability.

The Tullio Phenomenon in Patients with Meniere's Disease as Revealed with Posturography

The effect of low frequency sound (LFS) on postural stability was studied in 55 healthy volunteers and in 50 patients with Menière's disease. The sound levels ranged from 130 to 132 dB and were given at frequencies of 25, 50 and 63 Hz. The patients with Menière's disease displayed increased body sway during stimulation. In the individual response, 26% of the patients with Menière's disease experienced significant body sway. The results demonstrate that subjects with Menière's disease are sensitive to low frequency sound. The activation of vestibulo-spinal responses by low frequency sound seems to be a result of the Tullio phenomenon, in which sound energy activates the vestibular end-organ.

Positional nystagmus and body sway after alcohol ingestion

Positional nystagmus and body sway were measured for 8 hours following alcohol ingestion in 27 human volunteers. The intensity of positional alcohol nystagmus phase I (PAN-I) correlated well with blood alcohol concentration (BAC) along the time axis; the correlation coefficient between PAN-I and BAC 1 hour after alcohol ingestion was 0.62 ( P < .01). The minimum threshold BAC resulting in PAN-I was 0.23 mg/mL. Body sway was measured by stabilometry. The circumscribed area of posturography before and after alcohol ingestion was compared. Temporal changes in body sway and BAC were also closely correlated. The BAC threshold for increased body sway was estimated to be somewhere between 0.5 and 0.8 mg/mL, considerably higher than the threshold for PAN-I. Measurements of blood acetaldehyde, the dehydrated product of ethanol metabolism, showed no correlation with either the intensity of PAN or changes in body sway. The intensity of PAN and body sway measured at the time of peak BAC 1 hour after alcohol ingestion, however, showed significant positive correlation ( r = .50, n = 25; P < .01).

Computer‐analysed EEG and psychometric assessment of two new non‐benzodiazepine tranquillizers in healthy volunteers

AbstractThe effects on CEEG, psychomotor performance and attention of diazepam 10 mg, RU 43028 100 mg, RU 32698 100 mg and placebo administered orally have been investigated in 12 healthy subjects in a double‐blind controlled study. The effects of the compounds were evaluated by objective tests (CEEG, measurement of body sway, critical flicker fusion, visual reaction time, tapping test, arithmetical calculation) and subjective measurements (visual analogue scales and side‐effects questionnaire). Measurements were taken before treatment and after 30 min, 2 h, 3.5 h and 6.5 h. Placebo and RU 43028 did not affect any of the tests used. Diazepam induced an increase in beta rhythms and a decrease in theta and alpha rhythms on CEEG. These expected patterns were correlated with plasma concentrations. It also induced sedative side‐effects characterized by an increase of body sway and reaction time and a decrease of CFF and arithmetical calculation. RU 32698 displayed on atypical profile on CEEG with a reduction of alpha and theta rhythms without changes in beta and delta rhythms. It did not have any psychometric incapacitating effect.

Imbalance and Chronic Secretory Otitis Media in Children: Effect of Myringotomy and Insertion of Ventilation Tubes on Body Sway

We studied balance in 34 children with chronic secretory otitis media and compared them with 34 age- and sex-matched control children between the ages of 3 and 5 years. In addition to history and examination, objective measurements were obtained by use of a fixed force plate body sway platform in both the control group and the group with chronic secretory otitis media. We took measurements in both groups at an interval of 4 months to ensure that any improvement in body sway could not be attributed to normal maturation. Eight parameters of body sway were compared, including three new parameters not described elsewhere (mean squared velocity, the number of intersections, and velocity moment). Our study showed that balance is significantly worse in children with chronic secretory otitis media compared to a control group. Furthermore, the increased body sway of children with chronic secretory otitis media was returned to the normal range by myringotomy and insertion of ventilation tubes.

Evaluation and comparison of the interaction between alcohol and moclobemide or clomipramine in healthy subjects

The interaction of clomipramine and moclobemide with alcohol was compared in a double blind parallel groups study in 24 healthy volunteers. Moclobemide was given at the highest recommended therapeutic dose (200 mg t.i.d.) and clomipramine in a subtherapeutic dose (25 mg b.i.d.) because of its poor tolerance in healthy subjects. Psychometric evaluations were performed during a placebo run-in phase; after a 5-day treatment period; assessments were made before, and again 1 h and 4 h after alcohol ingestion. Alcohol doses were pre-determined for each subject in order to produce a blood alcohol concentration of 0.6 g/l 1 h after alcohol intake and this individual alcohol dose was given on test days. The day before alcohol intake tests for autonomic functions were made to assess the anticholinergic effects of the drugs. Alcohol significantly increased body sway, decreased critical flicker fusion frequency, prolonged choice reaction time, impaired copying skills, impaired memory and increased the subjective feelings of satisfaction and tension. Drugs increased the effect of alcohol on body sway and this was essentially due to clomipramine. Clomipramine both without and with alcohol increased body sway, prolonged choice reaction time more than did moclobemide. Clomipramine seemed to diminish alcohol-induced memory impairment in one of the memory tests used. Subjects taking clomipramine had significantly more adverse effects after alcohol ingestion than did subjects of the moclobemide group. In contrast to moclobemide, clomipramine produced a moderate but significant drop in standing systolic blood pressure and a clear inhibition of salivary excretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Significance of pressor input from the human feet in lateral postural control:The Effect of Hypothermia on Galvanically Induced Body-sway

The significance to human postural control of pressor information from the feet was investigated during vestibular disturbance in seven normal subjects who were exposed to bipolar biaural galvanic stimulation of the vestibular nerves before and after their feet were anaesthetized with hypothermia. The increase in body sway in the lateral plane induced by the galvanic stimulus was enhanced when the feet were anaesthetized, and adaptation of postural control to the galvanic stimulus was delayed. It is concluded that pressor information from the feet contributes significantly to postural control in humans and is important in compensating for vestibular disturbance.

Disability in anterior cruciate ligament insufficiency: An analysis of 19 untreated patients

We analyzed the knee function in 19 consecutive patients with chronic instability after an anterior cruciate ligament rupture. Muscle strength, standing balance, activity level, functional knee score, and a performance test were evaluated. Reduced quadriceps muscle strength compared with the noninjured limb was associated with reduced performance as measured by the one-leg hop test and the Lysholm knee score. No weakness in the hamstrings was found. The patients had impaired standing balance with increased body sway in the frontal plane when standing on both the injured and noninjured limb.

Risk Factors for Falls in a Community-Based Prospective Study of People 70 Years and Older

We investigated factors associated with falls in a community-based prospective study of 761 subjects 70 years and older. The group experienced 507 falls during the year of monitoring. On entry to the study a number of variables had been assessed in each subject. Variables associated with an increased risk of falling differed in men and women. In men, decreased levels of physical activity, stroke, arthritis of the knees, impairment of gait, and increased body sway were associated with an increased risk of falls. In women, the total number of drugs, psychotropic drugs and drugs liable to cause postural hypotension, standing systolic blood pressure of less than 110 mmhg, and evidence of muscle weakness were also associated with an increased risk of falling. Most falls in elderly people are associated with multiple risk factors, many of which are potentially remediable. The possible implications of this in diagnosis and prevention are discussed.

Posturography and the dizzy patient: a neurological study of 133 patients.

A total of 133 dizzy patients under the age of 60 years were examined using a stable balance plate (posturography, PG). All the patients were thoroughly examined neurologically before PG and classified into 7 diagnostic categories. Comparison was made between these categories and PG results. The referent group consisted of 116 healthy individuals. The patients with CNS lesions had more body sway than controls or the patients with peripheral vestibular lesions, whose sway did not significantly differ from that of the controls. The PG parameters that most clearly separated the patients from the controls were the total length of the movement of the center of gravity, and the sway in lateral and antero-posterior directions. Analysis of the frequency of the sway or calculation of the Romberg index did not reveal significant differences between the categories. Men swayed more than women. Age did not correlate with PG results. Stable posturography offers useful quantitative supplementary information as a part of the examination of a dizzy patient. Increased body sway suggests a lesion in the CNS.

Non-invasive estimation of afferent inputs for postural stability under low levels of alcohol.

The maintenance of human equilibrium is a complex process. Several physiological systems provide afferent information for postural stabilization. This study describes a noninvasive methodology to estimate the relative roles of interacting afferent inputs relevant for postural control. A multiaxis force platform in conjunction with specially designed test procedure provided semi-quantitative insight into the roles of vision, proprioceptors and vestibular apparatus in controlling postural sway when it was perturbed by a central nervous system perturbator such as alcohol. Experiments were conducted on 10 male and 10 female subjects. The males did not show statistically significant increases in body sway at these low levels of alcohol. For the females, the present methodology could detect subtle changes in postural sway at low blood alcohol levels ranging between 0.015% and 0.03%. At these low levels of alcohol, the results from females show that when the vision was excluded and the proprioception was modified, the postural sway was most affected. The postural instability experienced in this condition is probably due to inappropriate responses to proprioceptive inputs and lack of vision. Both male and female subjects showed a strong "eyes by standing surface" interaction. The proprioceptor manipulation alone did not affect the postural stability.

Improvement of ataxia in alcoholic cerebellar atrophy through alcohol abstinence.

Postural instability was measured and short, medium and long latency EMG responses to angular displacement of the ankle were recorded from leg muscles in a group of 17 alcoholics who presented with clinical signs of cerebellar atrophy of the anterior lobe. Recordings were performed twice (average interval 18.5 months) to determine the effects of continued drinking versus abstinence on the signs of the cerebellar damage. Patients who were abstinent (n = 11) exhibited a significant, sometimes dramatic decrease of body sway whereas patients who continued drinking (n = 6) showed increased body sway when the eyes were closed. Short and medium latency EMG responses were unaltered in both groups of patients. The integral of the long latency response of the antagonist tended to increase with continued abuse and to decrease in abstinent patients.

Effects of antidepressants on skilled performance.

Effects of amitriptyline 50 mg, desipramine 100 mg, and zimelidine 200 mg alone and in combination with ethanol 0.8 g/kg were investigated in healthy, male volunteers. Amitriptyline increased body sway and impaired tracking as well as information processing. It had an additive deleterious pharmacodynamic interaction with ethanol. Desipramine and zimelidine were free of adverse effects on performance and did not have significant interactions with ethanol. The dose of ethanol used in the present study did not inhibit biotransformation of the antidepressants.

Mechanisms of postural ataxia after intake of alcohol.

The effect of an acute intoxication with alcohol on the stability of stance was examined in 12 healthy subjects. They drank 11 of wine within 1 h. The resulting blood alcohol concentrations ranged between 0.9 and 1.67 mg/ml. Static posturography at the end of drinking and 1 h later revealed a significant increase in body sway which was mainly due to an increase in anteroposterior sway only present with closed eyes. A comparison of the results of posturography after acute intoxication with the data of patients with permanent lesions confined to the different functional subunits of the cerebellum shows that the acute effect of alcohol largely resembles that of a chronic lesion of the cerebellar anterior lobe (the spinocerebellum).

Risk factors for fractured neck of femur in the elderly.

During a 15-month period, 47 elderly female patients admitted to hospital with a fractured neck of femur were studied immediately prior to discharge, in comparison with 34 elderly female control patients undergoing elective surgery who had been admitted over the same period to the same orthopaedic wards. The principal differences between the two populations were that the fracture patients had a lower forearm trabecular bone density, with lower bodyweight (both lower muscle mass and lower fat content), increased body sway, worse eyesight and reduced mental acuity. The serum biochemistry of the two groups was almost indistinguishable except that the fracture patients tended to have slightly lower concentrations of proteins. There was no evidence to implicate dietary vitamin D deficiency, osteomalacia, oestrogen deficiency or alcoholism in the aetiology of the fracture, nor was there evidence to suggest alterations in endocrine function with respect to cacitonin or parathyroid hormone.

Effects of xylene and alcohol on vestibular and visual functions in man.

Ten healthy male volunteers were exposed for 4 h to two concentrations [6 and 11.5 mumol/l (636 and 1,218 mg/m3)] of m-xylene or/and given single doses (0.4 and 0.8 g/kg) of ethyl alcohol. Exposure to two xylene concentrations combined with the higher dose (0.8 g/kg) of alcohol was also conducted. Vestibular functions (positional nystagmus with electronystagmography, body balance) and visual function (flicker fusion) were measured. Both alcohol doses increased body sway and the intensity of nystagmus more than either concentration of xylene did, but they had little effect on visual functions. The effects of alcohol on vestibular functions were dose-dependent. The effects of xylene alone on the vestibular system were rather small, and those on the visual functions negligible. The combined effect of alcohol and the lower concentration of xylene (6 mumol/l) on body sway was additive, but the higher xylene concentration (11.5 mumol/l) antagonized the effect of alcohol on body sway and positional nystagmus. Two subjects experienced nausea and vomited exposure to alcohol and the higher xylene concentration. Mild impairment in visual functions was noted in the combined exposure. Alcohol significantly increased the blood m-xylene concentrations, a finding that suggests that their antagonism was pharmacodynamic rather than pharmacokinetic.

Saccadic eye movements and body sway.

Different conditions of moving retinal images show differential influences on postural stability. A surrounding pattern moved during steady fixation increases body sway, but similar image motions generated by voluntary saccades do not. Mechanisms for postural control do not respond to visual feedback during saccades. Analogous principles in saccadic suppression and space constancy are discussed.