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Biomedical subjects

A C Geurts

Publications and source records attributed to A C Geurts.

14 recordsLinked to original sources
PubMed2001

Postural control and cognitive task performance in healthy participants while balancing on different support-surface configurations.

Postural control during normal upright stance in humans is a well-learned task. Hence, it has often been argued that it requires very little attention. However, many studies have recently shown that postural control is modified when a cognitive task is executed simultaneously especially in the elderly and in the presence of pathology. This study examined postural control modifications when a cognitive task of varying difficulty levels is added. Postural stance difficulty was also varied. Results from this study suggest that a generalized capacity interference may occur due to the larger interference found with the addition of a cognitive task in the more novel and difficult postural task. Because the performance of the cognitive task was tapered by a speed-difficulty trade-off, it was not possible to determine whether a change in the level of difficulty of the cognitive task occurred and if it would produce larger dual-task interference.

Adult↗
PubMed2000

Postural control in rheumatoid arthritis patients scheduled for total knee arthroplasty.

OBJECTIVE: To investigate the use of compensatory visual and attentional control strategies for standing balance in patients with rheumatoid arthritis (RA) with severe knee joint impairment. DESIGN: Experimental 2-group design. SETTING: Specialized clinic for orthopedics, rheumatology, and rehabilitation in The Netherlands. PARTICIPANTS: Eighteen patients without comorbidity (age range, 65 +/- 7.7 yr; 16 women, 2 men) from a consecutive sample of patients with RA scheduled for total knee arthroplasty; 23 controls of the same age group also were tested (13 women, 10 men). MAIN OUTCOME MEASURES: By means of a dual-plate force platform, the velocity of center of pressure (COP) fluctuations were analyzed in the anteroposterior and lateral sway directions during quiet standing with eyes open, eyes closed, and while performing a secondary attention-demanding arithmetic task. RESULTS: Patients showed an average 80% greater COP velocity in both directions of sway compared with controls. In addition, stability deteriorated substantially more in patients than controls when deprived of visual information, which was associated with the degree of knee destruction. The effect of the arithmetic task was small and similar in patients and controls. CONCLUSION: RA patients with severe knee joint impairment can have a substantial basic postural instability; their relatively high reliance on visual information suggests impaired sensory feedback from the lower limbs. Current research is aimed at determining whether these postural deficits can be improved by total knee replacement.

Activities of Daily Living↗
PubMed2000

Kinematic assessment of manual skill following functional hand surgery in tetraplegia.

To determine whether surgical key grip reinforcement actually leads to a better movement ability we developed a procedure for the kinematic analysis of manual skill following hand surgery in tetraplegia. The functional results of surgery in 5 cases were examined by the kinematic analysis of drawing movements using an electronic pen and a digitizer under 3 conditions: with eyes open, with eyes closed, and while performing a concurrent arithmetic task. Movement velocity and dysfluency (ie, the number of velocity changes per centimeter) were measured before and at several moments after surgery during subsequent rehabilitation. Both movement velocity and dysfluency showed good stability across repeated trials and were consistently affected by visual deprivation. Movement velocity showed a 39% increment between the first and last assessment. Although grip strength increased in all patients, it was not associated with the change of movement velocity. These results suggest that other factors (eg, deep sensibility, cognition, muscle coordination) play a critical role in the ability to use improved grip force for controlling drawing movements and emphasize the value of a kinematic assessment besides measuring isolated grip force in the evaluation of functional hand surgery.

Adult↗
PubMed2000

Systematic review of aetiology and treatment of post-stroke hand oedema and shoulder-hand syndrome.

Studies on the aetiology and treatment of post-stroke hand oedema and shoulder-hand syndrome (SHS) published from January 1973 until August 1998 were identified. Eleven studies were included with at least some control for confounding. These were evaluated on 11 methodological criteria and by standardized effect sizes. There were five aetiological studies: four cohort studies and one study consisting of two case series using a within-subjects design. The matters investigated included lymph scintigraphy in hand oedema, bone scintigraphy, putative risk factors and the existence of autonomic dysregulation and peripheral nerve lesions in SHS. There were six therapeutic studies: one randomized controlled trial, one non-randomized controlled trial, one cohort study and three case series, of which two studies used a within-subjects design. These studies investigated continuous passive motion and neuromuscular stimulation in hand oedema as well as oral corticosteroids, intramuscular calcitonin and trauma prevention in SHS. A great diversity of pathophysiological and therapeutic insight was found. Based on systematic analysis of the literature, the following conclusions seem justified: (i) the shoulder is involved in only half of the cases with painful swelling of wrist and hand, suggesting a "wrist-hand syndrome" between simple hand oedema and SHS; (ii) hand oedema is not lymphoedema; (iii) SHS usually coincides with increased arterial blood flow; (iv) trauma causes aseptic joint inflammations in SHS; (v) no specific treatment has yet proven its advantage over other physical methods for reducing hand oedema; and (vi) oral corticosteroids are the most effective treatment for SHS.

Edema↗
PubMed1999

Is postural control associated with mental functioning in the persistent postconcussion syndrome?

OBJECTIVE: To investigate whether balance is associated with mental functioning after mild traumatic brain injury (MTBI). DESIGN: Experimental two-group design. SETTING: Outpatient rehabilitation department. PATIENTS AND OTHER PARTICIPANTS: From a consecutive sample of referred MTBI patients, 15 subjects who complained of imbalance were included (8 men and 7 women, age 35.9+/-8.6yrs). Subjects with detectable neurologic impairments were excluded. Twenty healthy control subjects of the same age group also were tested. MAIN OUTCOME MEASURES: In both groups, a force platform recorded center-of-pressure (CP) fluctuations during standing and weight shifting in different conditions. For the patients, attention and mental speed were assessed with the Symbol-Digit Substitution Test of the Wechsler Adult Intelligence Scale (Dutch version), verbal learning and memory were assessed with the 15-Words Test, and emotional distress was assessed with the Symptom Checklist-90. RESULTS: Compared with controls, patients showed an overall increase of 60% in CP velocity and an overall weight-shifting speed 25% slower (p < .005), indicating static and dynamic postural instability. Only performance on the Symbol-Digit Substitution Test was associated with both static and dynamic balance (p < .02), giving an explained variance of over 40%. CONCLUSION: The results indicate a possible association of balance with cognitive performance but not with emotional well-being after MTBI, suggesting an organic rather than a functional cause of postural instability. Further research is needed to assess the possible clinical implications.

Adult↗
PubMed1997

Axillary brachial plexus blockade for the reflex sympathetic dystrophy syndrome.

The reflex sympathetic dystrophy syndrome (RSD) is a neurogenic pain syndrome that is characterized by pain, vasomotor and dystrohic changes and often motor impairments. Although the exact pathogenesis of RSD is unknown, for long the sympathetic nervous system was thought to play a dominant role and pharmacological and surgical sympathectomies have been a mainstay in treatment procedures. However, there is growing evidence of a pivotal role of C- and A delta-fibres in the aetiology of RSD. These fibres subserve a dual sensory-effector function. Besides the initiation of afferent impulses, they release neuropeptide mediators that cause a peripheral neurogenic inflammatory reaction and central neuroplastic reactions. Brachial plexus blockade (BPB) with local anaesthetic drugs interferes with the conduction of action potentials along both sympathetic efferents and the somatosensory C- and A delta-afferents and therefore seems a potential treatment modality in RSD. The aim of this study was to draw attention on this regional anaesthetic technique that is not commonly used in RSD. In this study six patients with severe RSD of an upper extremity in varying stages were treated with BPB in the multidisciplinary setting of an out-patient rehabilitation clinic with a follow-up of 12 to 21 months. The study was not placebo controlled. Three patients responded well. In these cases the treatment interval varied from 3 to 6 months, one case had RSD stage 1 and the two others stage 2. Three patients showed poor response. In one of these patients the initial effect was good but due to an infection at the insertion site of the catheter BPB had to be discontinued. The other two poor-responders had treatment intervals of 7 and 25 months and both had stage 3 RSD. We conclude that there is theoretical and clinical support to further evaluate the effect of BPB as a treatment modality in the early stages of RSD.

Adult↗
PubMed1996

Identification of static and dynamic postural instability following traumatic brain injury.

OBJECTIVE: Quantitative evaluation of static and dynamic aspects of postural instability as a long-term consequence of traumatic brain injury (TBI). DESIGN: Experimental two-group design. SETTING: Outpatient rehabilitation department. PATIENTS AND OTHER PARTICIPANTS: From a consecutive sample of TBI patients at least 6 months after trauma, 20 subjects were selected who complained of reduced gross motor skills but showed no sensorimotor impairments in a standard neurological examination (11 men, 9 women; mean age 36.2 +/- 10.7 years). Thirteen patients had sustained mild, 2 moderate, and 5 severe TBI. Twenty healthy controls were matched for age and gender. INTERVENTION: None. MAIN OUTCOME MEASURES: A dual-plate force platform recorded the amplitude and velocity of the center-of-pressure fluctuations in the anteroposterior (AP) and lateral (LAT) sway directions during quiet standing. Also, the speed and fluency of weight shifting using visual feedback was registered. Both balance tasks were combined with an arithmetic task, whereas quiet standing was also tested with visual deprivation. RESULTS: Compared to controls, TBI patients showed an increase of over 50% in AP and LAT sway, and a weight-shifting speed 20% lower. Dual-task interference was never significant. Visual deprivation was most detrimental for the TBI patients, particularly for LAT sway control. CONCLUSION: A long-term overall reduction in both static and dynamic control of posture can be present after TBI, even in patients without clear neurological deficits. Force-plate recordings can identify such (latent) balance problems. Visual deprivation during quiet standing appears a simple, sensitive test for postural instability related to sensory integration deficits.

Adolescent↗
PubMed1994

Attention demands in balance recovery following lower limb amputation.

The attention demands in balance control after damage to the peripheral sensorimotor system were studied in 12 persons with a recent lower limb amputation. The interference of an arithmetic task with two postural tasks of different complexity (quiet standing and active weight shifting) was examined several times during their rehabilitation while the subjects stood on a force platform. Control data were obtained from healthy subjects. For both postural tasks, persons with amputation performed worse than controls. Quiet standing, a relatively simple task, revealed clear dual-task interference only in the amputation group. Evidence was found for a reduction in dual-task interference as rehabilitation progressed. In contrast, voluntary (feedback-controlled) weight shifting, a more complex task, revealed an equal amount of dual-task interference in persons with amputation and in controls, without changes in interference over the period of rehabilitation. The results indicate that attentional mechanisms may be involved in postural control, depending on both the novelty and complexity of the task. Moreover a reduction in attention demands of quiet standing may reflect a central adaptation of the postural organization to the peripheral sensorimotor impairments caused by lower limb amputation.

Journal Article↗
PubMed1993

Intrasubject variability of selected force-platform parameters in the quantification of postural control.

Platform stabilometry is increasingly applied to monitor or re-educate standing balance in clinical rehabilitation. Consequently, insight is needed into the validity, reliability, and sensitivity of different force-platform parameters. This study focuses on the intrasubject variability as the major source of variance (unreliability) in the study of human motor skills. The intrasubject variability of several, commonly applied force-platform parameters was determined across ten repeated tests of quiet two-legged standing in healthy subjects to identify the most consistent and stable parameters in the quantification of postural control. The variability of the root mean square (RMS) amplitude, peak-to-peak amplitude, mean frequency, and RMS velocity of the fore-aft and lateral components of the center-of-pressure fluctuations was investigated under varying (visual and cognitive) task conditions. The results indicate that all selected parameters show considerable intrasubject variability irrespective of the task context. Nonetheless, both the RMS amplitude and RMS velocity in either direction of sway do not demonstrate a significant trend across repeated tests. Among the selected parameters, the RMS velocity in the fore-aft direction shows the greatest intrasubject consistency, as well as a high sensitivity to, for example, visual deprivation. These findings support the reliability and validity of this parameter in the clinical quantification of postural control.

Adult↗
PubMed1992

Postural reorganization following lower limb amputation. Possible motor and sensory determinants of recovery.

Postural control was assessed in persons with a unilateral lower limb amputation before and after their rehabilitation. The centre-of-pressure fluctuations during quiet upright standing on a dual-plate force platform were registered with and without visual information in order to identify relevant determinants of balance restoration. In addition, static (weight distribution) as well as dynamic (control activity) asymmetry characteristics were examined. Besides a small improvement in balance control with full visual information (fore-aft sway, p less than 0.06; lateral sway, p less than 0.05), there was a major decrease in visual dependency (fore-aft and lateral sway, p less than 0.05) indicating a somatosensory re-integration process. Postural asymmetry in comparison with matched control subjects was most apparent and only significant in dynamic terms and remained constant across rehabilitation. It is concluded that after a lower limb amputation a central reorganization of postural control takes place, in which sensory determinants of motor recovery may play a critical role.

Aged↗
PubMed1992

Postural organization in patients with hereditary motor and sensory neuropathy.

The postural organization in patients with hereditary motor and sensory neuropathy (HMSN) type I or II was studied clinically by means of a force platform. Balance was registered in 14 barefooted HMSN patients and healthy matched control subjects during quiet stance. The effect of visual deprivation was tested to determine the degree of visual dependency. The effect of the simultaneous performance of a concurrent attention-demanding task (Stroop task) was tested to estimate the level of balance automaticity. In comparison with control subjects, the HMSN patients showed a basically decreased efficiency of postural control (p less than .01) as well as an increased visual control of posture (p less than .05) in both directions of sway. No loss of balance automaticity was found, which suggested an on-line central adaptation to the slowly developing peripheral impairments. The results provide a starting point for understanding the balance problems and gross motor disabilities in HMSN patients.

Adult↗
PubMed1991

Dual-task assessment of reorganization of postural control in persons with lower limb amputation.

Postural control in persons with lower limb amputation was studied using a cognitive approach to motor learning. The aim of this study was to show that an important characteristic of the central reorganization process after a lower limb amputation is the gradually decreasing need of attentional resources to perform a motor task. A dual-task procedure was developed to estimate the level of automaticity of a quiet, upright standing task. The effect of a concurrent attention-demanding task (Stroop task) on the efficiency of balance control was determined using force-platform measurements at the start and the end of the rehabilitation process. In contrast with a control group, the amputation group showed interference effects on body sway caused by the concurrent task both at the start (p less than .05) and, less severe, at the end of rehabilitation (p less than .05). Improvement of balance control was significant only for the dual-task condition (p less than .05). The results corroborated the hypothesis that dual tasks give information about the restoration of automaticity of postural control as an essential characteristic of the central reorganization process in persons with lower limb amputation. The role of dual-task procedures as a useful approach to skill assessment is discussed.

Adult↗