A dual-task study of interference between mental activity and control of balance

OBJECTIVE: This study aimed to examine interference between mental activity and control of balance. STUDY DESIGN: In a mixed design, dual-task study, the performance of patients and healthy control subjects was compared on computerized dynamic posturography, on a visuospatial mental task, and when performing the mental task while balancing. SETTING: The study was performed at a tertiary referral outpatient neuro-otology clinic. PATIENTS AND SUBJECTS: The patient group comprised 24 patients seen consecutively at the clinic because of vertigo and dizziness. The control group consisted of 24 subjects with no complaint or medical history of dizziness or balance disorder, matched with the patients for age and gender. MAIN OUTCOME MEASURES: Performance on a visuospatial mental task and on the computerized dynamic posturography test (conditions 4 and 5) was measured. RESULTS: Balancing on the posturography test resulted in a deterioration in performance on the mental task for both patients and control subjects. The effect was more marked when subjects had their eyes closed. Results on the balance test showed that normal subjects and patients with normal balance also swayed more when performing the mental task, whereas patients who had failed the posturography test swayed less when performing the mental task. CONCLUSIONS: These results show that mental performance deteriorates when performing a demanding balance task. In addition, in both normal subjects and patients, balance also may be affected by mental activity in complex and varied ways that merit further investigation.     

Regulation and function of tinman during dorsal mesoderm induction and heart specification in Drosophila

Sensory-motor control of upright human posture may be organized in a top-down fashion such that certain head-trunk coordination strategies are employed to optimize visual and/or vestibular sensory inputs. Previous quantitative models of the biomechanics of human posture control have examined the simple case of ankle sway strategy, in which an inverted pendulum model is used, and the somewhat more complicated case of hip sway strategy, in which multisegment, articulated models are used. While these models can be used to quantify the gross dynamics of posture control, they are not sufficiently detailed to analyze head-trunk coordination strategies that may be crucial to understanding its underlying mechanisms. In this paper, we present a biomechanical model of upright human posture that extends an existing four mass, sagittal plane, link-segment model to a five mass model including an independent head link. The new model was developed to analyze segmental body movements during dynamic posturography experiments in order to study head-trunk coordination strategies and their influence on sensory inputs to balance control. It was designed specifically to analyze data collected on the EquiTest (NeuroCom International, Clackamas, OR) computerized dynamic posturography system, where the task of maintaining postural equilibrium may be challenged under conditions in which the visual surround, support surface, or both are in motion. The performance of the model was tested by comparing its estimated ground reaction forces to those measured directly by support surface force transducers. We conclude that this model will be a valuable analytical tool in the search for mechanisms of balance control.     

Posturography does not test vestibulospinal function

The clinical usefulness of posturography is unknown, despite its costing more than +500 per test in some areas of the United States, including Boston. We cross-sectionally and prospectively studied blinded vestibulo-ocular and vestibulospinal tests from 29 stable patients with chronic vestibular hypofunction; 22 patients were affected bilaterally (BVH), and 7 were affected unilaterally (UVH). Vestibulo-ocular function was assessed by electronystagmographic caloric stimulation and sinusoidal vertical axis rotation gains at 0.05 Hz. Vestibulospinal function was assessed by moving-platform and visualsurround posturography sensory organization tests (SOTs), paced and free gait in a gait laboratory, and clinical tests of timed gait and standing. Posturography SOT moving-platform tests 4 through 6, designed to assess vestibular function, correlated significantly (r < or = 0.72, P > or = 0.01) with vestibulo-ocular tests in 5 of 6 comparisons among BVH patients. Posturography SOT results, however, correlated poorly with other vestibulospinal measures: correlations were statistically significant for only 7 of 18 comparisons with clinical balance and gait function (r < or = 0.69, P > or = 0.01) and with 2 of 12 comparisons for gait laboratory dynamic stability measures (r < or = 0.55, P > or = 0.01) among the BVH patients. When both the platform and visual surround moved (SOT 6), however, correlations were statistically significant with static standing clinical measures (r = 0.51 to 0.69, P < 0.01) and with whole-body maximum moment arm during paced gait (r = 0.55, P < 0.01). Posturography scores for the UVH patients did not significantly correlate with any vestibulo-ocular or other vestibulospinal measures. These data indicate that among patients with BVH posturography SOT scores relate at best modestly with accepted measure of vestibulo-ocular function, less well with clinical measures of balance control, and poorly with dynamic gait-performance measures. We conclude that posturography SOT does not assess vestibulospinal function.     

Dizziness from whiplash and head injury: differences between whiplash and head injury

OBJECTIVE: Large discrepancies exist in the literature regarding incidence and types of symptomatology in whiplash. This is because of the evolution of whiplash injury over the years with the advent of head rests and seat belts. Previous authors have regarded symptoms of dizziness as a result of brainstem or cerebellar injury or both. It has been difficult in those studies to ascribe a mechanism of injury, as patients with whiplash injury only have been grouped with those who have incurred mild traumatic brain injury as a result of a significant blow to the head. The authors saw the need to delineate patients who had suffered whiplash injury from those who also had suffered mild head injury, as defined in the rehabilitation-neurosurgical literature, to attempt to define differences in symptoms, abnormalities, and mechanisms of recovery in these two groups. STUDY DESIGN: The study design was a retrospective case review. SETTING: The study was conducted at a tertiary-quaternary referral clinic. PATIENTS: The records of 36 patients were reviewed. Nineteen of these patients suffered a whiplash-associated disorder and 17 suffered a mild head injury as well. These patients were referred for assessment of symptoms persisting for at least 2 years after their injury. Patients were excluded if they had not completed clinical assessment, including electronystagmography (ENG) and computerized dynamic posturography (CDP). INTERVENTIONS: A full history, otolaryngologic examination, including assessment of eye movements, corneal reflexes and gait, as well as an investigation, including ENG and CDP, and history taking and detailed recording of related complaints immediately before diagnostic work-up were performed. MAIN OUTCOME MEASURES: Symptoms reported by patients who had received either whiplash alone or whiplash plus mild head trauma as defined in the literature were measured. Patients were classified according to type of accident, type of injury suffered, and degree and nature of posturographic abnormalities. RESULTS: Patients often have similar complaints regardless of whether or not they had suffered a head injury. Although CDP showed abnormalities in both groups, standard ENG assessment, including caloric testing, showed abnormalities only in the head-injured group. The posturographic abnormalities also were analyzed in both groups, and it was found that there was a correlation between the type of posturographic abnormality and the type of injury suffered. Although ENG testing is done routinely, posturography is shown to be more sensitive in picking up abnormalities. In addition, the authors have shown that posturography can delineate the type of injury suffered by exhibiting the compensation strategy used as well as the efficacy of that compensation strategy. CONCLUSIONS: Because ENG abnormalities are limited to patients who have suffered a head injury, the inference is that these two groups of patients have suffered damage at different sites along the balance system pathways, but both of these lesions can lead to similar symptoms. Although the mechanisms of whiplash injury and how they affect the vestibular system are poorly understood, posturography testing is essential in inferring how a patient is recovering by measuring how and how well the patient is overcoming his or her deficit. This has important medical legal implications regarding legitimizing a patient's problem, prognostic factors, as well as rehabilitation plans, measures, and outcomes.     

Concept identification and practice in brain-damaged and process-reactive schizophrenic groups.

A nonverbal concept identification task involving easy and difficult subtests was given to groups of process and reactive schizophrenic, brain-damaged, and control patients. The same test was administered twice. Brain-damaged and process schizophrenic groups had poorer overall performance than the other 2 groups but did not differ from each other significantly. However, patterns of improvement on the easy and difficult subtests were different for the schizophrenic vs. brain-damaged groups. Implications for "organic" vs. "functional" explanations of process schizophrenia were discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transsexualism

Stabilometry, which measures the body's center of pressure (COP) movements, during relaxed standing, has been used to distinguish individuals with vestibular and neurologic dysfunctions from normal subjects. The purpose of this study was to determine whether mathematical differences in the magnitudes of the COP obtained from six somatosensory testing conditions could be used to discriminate between different types of balance deficits. Stabilometry measures, using a fixed force platform, were obtained from normal (N = 52) and dizzy (N = 149), peripheral vestibular dysfunction (PVD), post-concussion syndrome (PCS), psychogenic (PSG), and unknown/undetermined etiology (UNK). The data significantly differentiated CVD, PVD and PSG patients from normals and between some of the dizzy groups: CVD versus PVD, PCS; and PSG versus CVD, PVD, PCS and UNK. The measures of anterior-posterior COP movements provided the greatest discrimination.     

The efficacy of ciprofloxacin and doxycycline against experimental tularaemia

A group of patients with balance complaints (n = 16) was compared with a group of normal subjects (n = 17) by means of posturography, subjective assessments of balance, anxiety and unsteadiness when standing on a force platform with eyes closed. Postural instability was induced by vibratory stimulation of the calf muscles (20, 40, 60, 80 and 100 Hz). As a control condition, the arm (biceps) was stimulated at similar frequencies. In order to control for arousal, blood pressure and heart beat were assessed. Furthermore, questionnaire responses on psychological measures were collected. Results showed clear differences between the groups in terms of imbalance and self-reports. However, the 2 groups displayed similar increases of imbalance during calf stimulation and no increase during arm stimulation. Patients generally rated less increase of unsteadiness when the calf was stimulated than did the controls. No differences in arousal were found between the groups or within conditions. Results are discussed in terms of the proposed desynchrony between symptoms and complaints.     

Influence of visual control, conduction, and central integration on static and dynamic balance in healthy older adults

Aging is associated with decreased balance abilities, resulting in an increased risk of fall. In order to appreciate the visual, somatosensory, and central signals involved in balance control, sophisticated methods of posturography assessment have been developed, using static and dynamic tests, eventually associated with electromyographic measurements. We applied such methods to a population of healthy older adults in order to appreciate the respective importance of each of these sensorial inputs in aging individuals. Posture control parameters were recorded on a force-measuring platform in 41 healthy young (age 28.5 +/- 5.9 years) and 50 older (age 69.8 +/- 5.9 years) adults, using a static test and two dynamic tests performed by all individuals first with eyes open, then with eyes closed. The distance covered by the center of foot pressure, sway area, and anteroposterior oscillations were significantly higher, with eyes open or closed, in older people than in young subjects. Significant differences were noted in dynamic tests with longer latency responses in the group of old people. Dynamic recordings in a sinusoidal test had a more regular pattern when performed eyes open in both groups and evidenced significantly greater instability in old people. These data suggest that vision remains important in maintaining postural control while conduction and central integration become less efficient with age.     

Identification and characterization of two thrombin-activatable fibrinolysis inhibitor isoforms

OBJECT: The indications, operative findings, and outcomes of vestibular schwannoma microsurgery are controversial when it is performed after stereotactic radiosurgery. To address these issues, the authors reviewed the experience at two academic medical centers. METHODS: During a 10-year interval, 452 patients with unilateral vestibular schwannomas underwent gamma knife radiosurgery. Thirteen patients (2.9%) underwent delayed microsurgery at a median of 27 months (range 7-72 months) after they had undergone radiosurgery. Six of the 13 patients had undergone one or more microsurgical procedures before they underwent radiosurgery. The indications for surgery were tumor enlargement with stable symptoms in five patients, tumor enlargement with new or increased symptoms in five patients, and increased symptoms without evidence of tumor growth in three patients. Gross-total resection was achieved in seven patients and near-gross-total resection in four patients. The surgery was described as more difficult than that typically performed for schwannoma in eight patients, no different in four patients, and easier in one patient. At the last follow-up evaluation, three patients had normal or near-normal facial function, three patients had moderate facial dysfunction, and seven had facial palsies. Three patients were incapable of caring for themselves, and one patient died of progression of a malignant triton tumor. CONCLUSIONS: Failed radiosurgery in cases of vestibular schwannoma was rare. No clear relationship was demonstrated between the use of radiosurgery and the subsequent ease or difficulty of delayed microsurgery. Because some patients have temporary enlargement of their tumor after radiosurgery, the need for surgical resection after radiosurgery should be reviewed with the neurosurgeon who performed the radiosurgery and should be delayed until sustained tumor growth is confirmed. A subtotal tumor resection should be considered for patients who require surgical resection of their tumor after vestibular schwannoma radiosurgery.     

The vestibular & balance center: tools for diagnosing the dizzy patient

Without access to adequate diagnostic facilities, management of vestibular and balance disorders can be a frustrating process for both clinicians and patients. Expert clinical staff and state-of-the-art tools for the evaluation of balance disorders and dizziness are available within the vestibular and balance center. These centers can provide referring physicians and their patients with access to diagnostic expertise and facilities not practical within a general practice environment. Providing detailed evaluative reports, balance centers can help the referring physician define directions for surgical and medical treatment and assist in the management and rehabilitative treatment of acute and chronic dizziness and balance dysfunction.     

Maximal functional capacity in patients with endomyocardial fibrosis

We evaluated objectively the cardiocirculatory dysfunction of patients with EMF, and related the functional class (FC-NYHA) to the data obtained by analysis of maximal functional capacity. We studied 55 subjects, divided into three groups: group 1 (G1) 21 (38.1%) normal persons, group 2 (G2) seven (12.7%) patients with EMF who were in FC I or II, and group 3 (G3) 27 (49%) patients in FC III or IV. Maximal oxygen consumption (VO2max) and O2 pulse index (PO2max) were obtained using a Beckman computerized gas analyser. The mean values were significantly different among the three groups. We conclude that the greater the clinical impairment, the greater the alterations that occur in the indices of cardiac function.     

Functional outcome of vestibular rehabilitation in patients with abnormal sensory-organization testing

A goal of vestibular rehabilitation is to improve the functional status of patients with balance disorders. Despite the focus of vestibular rehabilitation on function, few objective data describe the outcome of vestibular rehabilitation in terms of balance function. In this prospective observational study, we tested a well-defined patient cohort (n = 67) with abnormal pretreatment sensory-organization testing who were undergoing vestibular rehabilitation. Patient outcomes were determined by using objective and subjective measures of function before and after rehabilitation. Overall, 60% of patients showed objective improvement of balance function; 25% of patients improved to normal. Analysis of success and failure of vestibular rehabilitation is important as an aid to appropriate patient counseling and efficient use of rehabilitation resources.     

Influence of heroin addiction of neuropsychological functioning.

Compared performance of 25 heroin-addicted veterans, 25 brain-damaged veterans, and 25 normal controls on the Halstead Impairment Index. All subtests significantly discriminated between the brain-damaged group and the heroin-addicted and normal groups, but there were no significant differences between the latter 2 groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of certain language and communication environments in early childhood on the development of language in deaf individuals

Four groups of deaf subjects between the age of 10-0 and 18-11 years were tested, employing the Test of Syntactic Ability, and the language subtests of the Stanford Achievement Test, in a study of the influence of early language and communication environment on later syntactic language ability. The groups, 18 subjects in each, were dichotomized by whether the parents were hearing or deaf and further subgrouped by the language ability of the parents if the parents were deaf, and by the amount and intensity of oral preschool training provided by the parents if the parents were hearing. The groups were labeled by the type of language used with them in infancy and early childhood: manual English, average manual, intensive oral, and average oral. Results showed significant superiority of the manual English group over the two oral groups on five of the six major test structures of the Test of Syntactic Ability. On the Stanford Achievement Test, the manual English group performed significantly better than the other three groups on all four subtests. The two manual groups performed significantly better than the two oral groups on every test measure employed.     

Clinimetrics of postural instability in Parkinson's disease

Judgement of the ability to recover balance after a sudden shoulder pull is used as a clinical measure of postural instability in Parkinson's disease. To further evaluate its merits, we compared this 'retropulsion test' with dynamic posturography in 23 Parkinson patients. Dynamic posturography involved 20 serial 'toe-up' support surface rotations, which induced backward body sway. We found a moderate correlation (Spearman's p = 0.54; P < 0.05) between the retropulsion test and body sway after platform rotations during the 'off' phase, but no correlation during the 'on' phase (Spearman's p = 0.43; P = 0.11). These results cast doubt on the use of the retropulsion test as a measure of postural instability in Parkinson's disease.     

Age-associated differences in sensori-motor function and balance in community dwelling women

Tests of visual, vestibular, sensori-motor and balance function were administered to 550 women, aged between 20 and 99 years at a Balance and Gait Laboratory. All of the sensory, motor and balance system measures showed significant age-associated differences. Multiple regression analyses revealed that the measures of lower limb sensation were the consistent sensori-motor factors contributing to balance under normal conditions (standing on a firm surface with eyes open or closed). Under more challenging conditions (standing on foam with eyes open) vision, strength and reaction time played significant roles, whilst when standing on foam with eyes closed, vestibular function also made a significant contribution. Analysis of percentage increases in sway under conditions where visual and peripheral sensation systems were removed or diminished, compared with sway under optimal conditions, indicated that up until age 65 there was an increased reliance on vision for balance control. Beyond this age, the contribution made by vision declined, so that in the oldest age-groups reduced vision was less able to supplement peripheral input, resulting in increased sway areas. Peripheral sensation however was the most important sensory system in the maintenance of static postural stability at all ages.     

Organicity versus old age in objective and projective test performance.

Administered the WAIS and the Holtzman Inkblot Technique (HIT) to 322 Veterans Administration domiciliary members to gain information on the nature and extent of intellectual decline from age 45-84. Multivariate statistical analyses were utilized to examine configural relationships among 4 aging groups compared with a group diagnosed as chronic brain syndrome. Multiple discriminant analysis revealed an overall statistically significant difference among the 5 group profiles. The 1st discriminant function tended to define the aging process by separating the 4 age groups. The 2nd discriminant function revealed a different patterning of test scores to be identified with the separation of the chronic brain syndrome group from the normal aging groups. Results based on 11 WAIS subtests and on 17 HIT variables were substantially similar. A final analysis utilizing both WAIS and HIT subtests revealed clearly that old age differs from younger age groups along a continuum that is quite different from that separating chronic brain syndrome patients from normal aging groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Normalization of abnormal coronary vasomotion by calcium antagonists in patients with hypertension

BACKGROUND: Endothelial dysfunction with a loss of endothelium-dependent vasodilation has been reported in patients with arterial hypertension. The purpose of the present study was to evaluate coronary vasomotor response to dynamic exercise in patients with coronary artery disease with and without arterial hypertension and to determine the effect of calcium antagonists on coronary vasomotion. METHODS AND RESULTS: Cross-sectional areas of a normal and a stenotic coronary vessel segment were examined in 79 patients with coronary artery disease at rest and during supine bicycle exercise (Ex). Change in luminal area after acute administration of a calcium antagonist (diltiazem or nicardipine), during exercise, and after sublingual nitroglycerin (percent change compared with rest = 100%) was assessed by biplane quantitative coronary arteriography. Patients were divided into two groups: Group 1 (control) consisted of 48 patients without (normotensive subjects, n = 30; hypertensive subjects, n = 18) and group 2 of 31 patients with (normotensive subjects, n = 15; hypertensive subjects, n = 16) pretreatment with a calcium antagonist immediately before exercise. The groups did not differ with regard to clinical characteristics or hemodynamic data measured during exercise. Mean aortic pressure at rest, however, was significantly increased in hypertensive patients compared with normotensive subjects in group 1 (103 mm Hg versus 92 mm Hg, P < .01) and group 2 (110 mm Hg versus 98 mm Hg, P < .025). In group 1, exercise-induced vasomotor response was significantly different between normotensive and hypertensive patients in normal (+20% versus +1%, P < .003) and stenotic vessels (-5% versus -20%, P < .025). However, in group 2 there was coronary vasodilation in normotensive and hypertensive patients for both normal (delta Ex +23% versus +21%, P = NS) and stenotic vessel segments (+24% versus +26%, P = NS). CONCLUSIONS: Abnormal coronary vasomotion during exercise can be observed in hypertensive patients with reduced vasodilator response in normal arteries and enhanced vasoconstrictor response in stenotic arteries. Calcium antagonists prevent the abnormal response of normal and stenotic coronary arteries to exercise in hypertensive patients and thus may compensate for endothelial dysfunction with reduced vasodilator response to exercise.     

The vestibulo-ocular reflex in pupils at a Dutch school for the hearing impaired; findings relating to acquired causes

The vestibulo-ocular reflex was evaluated with caloric tests and velocity step (VS) tests in 121 pupils at a school for the hearing-impaired. Vestibular impairment was found in a total of 50 pupils (41%). It was found in 17 out of the 33 (52%) pupils with acquired causes of hearing impairment and significantly more often in pupils with a pure tone hearing threshold of more than 90 dB than in those with a lower threshold. In the group with prenatal causes, 5 out of 8 rubella cases showed vestibular impairment. Four of these cases had impaired VS responses and normal caloric responses. The high proportion of vestibular impairment in the group with postnatal causes was due to 5 cases with meningitis, all of whom showed caloric weakness. Kernicterus was significantly associated with vestibular hyperreactivity (5 cases out of 7), presumably due to a central dysfunction.     

The incomplete equivalence of the paper-and-pencil and computerized versions of the General Aptitude Test Battery.

The performance of 163 applicants for the Dutch Royal Military Academy on the computerized version of the General Aptitude Test Battery (GATB) was compared with the performance of 163 matched applicants on the paper-and-pencil version. There was a modest but clearly discernible influence of computerization. A LISREL analysis showed a reasonable fit for a model postulating two factors that were equally patterned for both test versions. A model postulating equal factor loadings had to be rejected. Individual differences in both the computerized and conventional GATB were strongly related to intelligence. The computerized subtests produced faster and more inaccurate responses than the conventional subtests. Both in terms of number of solved items and correlations with other cognitive measures, the cognitively simple, clerical tests were more affected by computerization than the more complex tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)