PubMed Health⌕ Search

Biomedical subjects

A C H Geurts

Publications and source records attributed to A C H Geurts.

10 recordsLinked to original sources
PubMed2006

Abnormalities in the temporal patterning of lower extremity muscle activity in hemiparetic gait.

Following hemiparetic stroke, the timing of lower extremity muscle activity during gait often undergoes radical changes. In the present study, we compared the duration of activity in Biceps femoris (BF), Rectus femoris (RF), Tibialis anterior (TA) and Gastrocnemius medialis (GM) for four subphases of the gait cycle: the first double support phase (DS1), the single support phase (SS), the second double support phase (DS2) and the swing phase (SW) and compared these between 24 hemiparetic stroke patients and 14 healthy controls. In the upper leg, durations of BF and RF activity during SS were significantly longer on the paretic side (70% for BF, and 78% for RF) as well as on the nonparetic side (71% for BF, and 81% for RF), when compared to controls (45% and 53% for BF and RF, respectively). As a result, the duration of BF-RF coactivity during SS was longer in both legs of patients with stroke (61% in the paretic and 62% in the nonparetic leg) relative to control values (25%). In addition, during DS1 of the paretic leg, the total amount of BF-RF coactivity was abnormally long (82% versus 57% in controls). In the lower leg, longer total durations of GM activity were found during DS1 on the paretic side in people with stroke (51%) than in controls (38%). In the paretic TA, longer durations of activity were observed during SW (73% versus 60% in controls), whereas smaller total durations of activity were found during SS (28% versus 48% in controls). No statistically significant differences were found between the paretic and nonparetic leg within patients, except for the mean total duration of TA activity during DS1 (50% and 69% for the paretic and nonparetic leg, respectively). Overall, these results suggest that, despite large interindividual differences, some common disturbances can be observed in the temporal layout of muscle activity and coactivity associated with hemiparetic gait. Although these disturbances are more pronounced in the paretic leg, muscle activation patterns of the nonparetic leg also display some clear abnormalities.

Adult↗
PubMed2006

Dynamical structure of center-of-pressure trajectories in patients recovering from stroke.

In a recent study, De Haart et al. (Arch Phys Med Rehabil 85:886-895, 2004) investigated the recovery of balance in stroke patients using traditional analyses of center-of-pressure (COP) trajectories to assess the effects of health status, rehabilitation, and task conditions like standing with eyes open or closed and standing while performing a cognitive dual task. To unravel the underlying control processes, we reanalyzed these data in terms of stochastic dynamics using more advanced analyses. Dimensionality, local stability, regularity, and scaling behavior of COP trajectories were determined and compared with shuffled and phase-randomized surrogate data. The presence of long-range correlations discarded the possibility that the COP trajectories were purely random. Compared to the healthy controls, the COP trajectories of the stroke patients were characterized by increased dimensionality and instability, but greater regularity in the frontal plane. These findings were taken to imply that the stroke patients actively (i.e., cognitively) coped with the stroke-induced impairment of posture, as reflected in the increased regularity and decreased local stability, by recruiting additional control processes (i.e., more degrees of freedom) and/or by tightening the present control structure while releasing non-essential degrees of freedom from postural control. In the course of rehabilitation, dimensionality stayed fairly constant, whereas local stability increased and regularity decreased. The progressively less regular COP trajectories were interpreted to indicate a reduction of cognitive involvement in postural control as recovery from stroke progressed. Consistent with this interpretation, the dual task condition resulted in less regular COP trajectories of greater dimensionality, reflecting a task-related decrease of active, cognitive contributions to postural control. In comparison with conventional posturography, our results show a clear surplus value of dynamical measures in studying postural control.

Aged↗
PubMed2005

Gait recovery is not associated with changes in the temporal patterning of muscle activity during treadmill walking in patients with post-stroke hemiparesis.

OBJECTIVE: To establish whether functional recovery of gait in patients with post-stroke hemiparesis coincides with changes in the temporal patterning of lower extremity muscle activity and coactivity during treadmill walking. METHODS: Electromyographic (EMG) data from both legs, maximum walking speed, the amount of swing phase asymmetry and clinical measures were obtained from a group of post-acute patients with hemiparesis, as early as possible after admission in a rehabilitation centre (mean time post-stroke 35 days) and 1, 3, 6, and 10 weeks later, while all patients participated in a regular rehabilitation program. EMG data from the first assessment were compared to those obtained from a group of healthy controls to identify abnormalities in the temporal patterning of muscle activity. Within subject comparisons of patient data were made over time to investigate whether functional gait recovery was accompanied by changes in the temporal patterns muscle (co-)activity. RESULTS: EMG patterns during the first assessment showed a number of abnormalities on the paretic side, namely abnormally long durations of activity in biceps femoris (BF) during the single support (SS) phase and in gastrocnemius medialis (GM) during the first double support phase (DS1). Furthermore, in both legs a prolongation of the activity was seen in the rectus femoris (RF) during the SS phase. In addition, the duration of BF-RF coactivation was longer on the paretic side than it was in controls. Over time, the level of ambulatory independence, body mobility, and maximum walking speed increased significantly, indicating that substantial improvements in gait ability occurred. Despite these improvements, durations of muscle (co-) activity and the level of swing phase asymmetry did not change during rehabilitation. More specifically, timing abnormalities in muscle (co-)activity that were found during the first assessment did not change significantly, indicating that these aberrations were not an impediment for functional gait improvements. CONCLUSIONS: Normalization of the temporal patterning of gait related muscle activity in the lower extremities is not a prerequisite for functional recovery of gait in patients with post-stroke hemiparesis. Apparently, physiological processes other than improved temporal muscular coordination must be important determinants of the restoration of ambulatory capacity after stroke. SIGNIFICANCE: Recovery of walking ability in post-stroke hemiparesis is not necessarily associated with, or dependent on, reorganization in the temporal control of gait related muscle activity. Normalization of the temporal coordination of muscle activity during gait may not be an important clinical goal during post-acute rehabilitation.

Adult↗
PubMed2004

Step characteristics during obstacle avoidance in hemiplegic stroke.

Whereas several animal studies have indicated the important role of the motor cortex in the control of voluntary gait modifications, little is known about the effects of cortical lesions on gait adaptability in humans. Obstacle avoidance tasks provide an adequate paradigm to study the adaptability of the stepping pattern under controlled, experimental conditions. In the present study, an exploratory assessment was made of the failure rate, the preferred stepping strategies (step lengthening vs step shortening), and the spatiotemporal stride characteristics (percentage increases in stride length, duration, and velocity of the crossing and postcrossing strides) during obstacle avoidance in 11 hemiplegic stroke patients and seven healthy controls. Patients were less successful in avoiding obstacles than controls (14% failure rate vs 0.5% in controls), independent of whether the affected or the unaffected leg led the obstacle avoidance. The number of failed trials increased systematically when the available response time became shorter. During successful trials, lengthening of the step was generally preferred over shortening. This bias towards step lengthening was more pronounced in stroke patients (step lengthening in 91% of the trials vs 75% in controls), irrespective of the side of obstacle presentation. For both groups, overall strategy preference did not adhere to a principle of minimal foot displacement, since step lengthening was used even if it would be more spatially efficient to shorten the step. No statistically significant group differences were found for the increases in length, duration, and velocity of the crossing and postcrossing strides. However, for a subgroup of more slowly walking patients, large percentage increases were found in crossing stride length, duration, and velocity. Similar results were obtained for the postcrossing stride, indicating that, for this subgroup of patients, restoration of the normal walking cadence was more difficult. Overall, no systematic differences were found between the affected and the unaffected leg in stroke patients with respect to failure rates, stepping strategies, or spatiotemporal measures of obstacle avoidance. The present findings suggest that the ability to adequately modify the stepping pattern in response to imposed spatiotemporal constraints is impaired in persons with stroke, especially when modifications have to be performed under time pressure. In addition, the stepping strategies employed by subjects with stroke are different from those found in controls, possibly to reduce the complexity of the avoidance maneuver and to enhance safety. Finally, unilateral cortical damage results in an impaired ability to avoid obstacles on both sides of the body, suggesting that the reduced ability of stroke patients to negotiate obstacles may be related to problems of a more general coordinative nature.

Adult↗
PubMed2004

Speed related changes in muscle activity from normal to very slow walking speeds.

The study of neuromuscular activity at very slow walking speeds may lead to a better understanding of the mechanisms underlying speed regulation during walking, and may aid the interpretation of gait data in patients who walk slowly. Extreme reductions in walking speed will cause changes in locomotor task demands that may eventually result in modifications of the patterning of muscle activity that underlies walking. The aim of the present study was to investigate patterns of lower limb muscle activity during very slow walking (< 0.28 m s(-1)), and to study the neuromuscular gain functions that reflect the phase dependent effects of walking speed on electromyographic (EMG) amplitude. Nine healthy young adults walked at seven different walking speeds (1.39, 0.83, 0.28, 0.22, 0.17, 0.11, and 0.06 m s(-1)) while EMG was recorded from eight lower extremity muscles. Results showed that the phasing of muscle activity remained relatively stable over walking speeds despite substantial changes in its amplitude. However, between 1.39 and 0.28 m s(-1), epochs of Rectus femoris, Biceps femoris and Tibialis anterior activities were found that were typical for specific speed ranges. When walking speed decreased further to almost standing still (0.06 m s(-1)), negative gain values were found in Peroneus longus during midstance and Rectus femoris in late swing, indicating the emergence of new bursts of activity with decreasing walking speed. It is proposed that these extra activities may be attributed to increased demands on postural stability, and the altered dynamics of the swinging limb at very slow speeds.

Adult↗
PubMed2004

Positive behavioural disturbances in the rehabilitation phase after severe traumatic brain injury: an historic cohort study.

PRIMARY OBJECTIVE: To investigate the association of post-traumatic amnesia (PTA) with positive behavioural disturbances (PBD) in an historic cohort of patients with severe traumatic brain injury (TBI) and to evaluate the use and effects of neuroleptic drugs in this cohort. RESEARCH DESIGN: Historic cohort study. METHODS: The medical files of 60 patients with severe TBI, selected for inpatient rehabilitation during a period of 5.5 years, were independently examined for the presence of PTA and PBD at admission in the rehabilitation centre as well as for the concomitant use of neuroleptic drugs. All TBI patients with PBD at admission were subjected to special nursing measures consisting of a structured and safe environment, a minimum number of caregivers and provision of simple and consistent feedback. As a basic policy, the use of neuroleptic medication was minimized or stopped. RESULTS: Of the 28 patients suffering from PTA at admission, 16 demonstrated PBD (positive predictive value 0.57 (95% CI 0.45-0.70)). In contrast, all the 32 patients without PTA but one did not show PBD (negative predictive value 0.97 (95% CI 0.93-1.00)). Seven of the 17 patients with PBD (41%) had been prescribed neuroleptic medication, of whom five patients (81%) experienced undesired side effects. Because of the special nursing measures, these drugs could be stopped or substituted by non-neuroleptic behaviour-modifying drugs in all patients within 3 weeks, without aggravation of their PBD. CONCLUSIONS: These results suggest that impaired attention and memory may play a critical role in the development of PBD in patients with severe TBI. From this perspective, maximum effort must be made to improve TBI patients' level of attention, memory and orientation instead of using mechanical or chemical restraints.

Adult↗
PubMed2003

Pharmacologic treatment of poststroke depression: a systematic review of the literature.

UNLABELLED: CLINICAL QUESTION/OBJECTIVE: A systematic evaluation of the literature published from 1966 until December 2001 on pharmacologic interventions for poststroke depression (PSD). DESIGN: Articles were selected from a computer-based search and were independently reviewed by three evaluators using a standardized criteria including internal validity items as well as descriptive and quantitative items. RESULTS: Fifty studies were preliminarily reviewed and 10 randomized controlled trials (RCTs) were included for systematic analysis. CONCLUSION: Selective serotonin reuptake inhibitors (citalopram and fluoxetine) may be effective in the treatment of PSD. There is some evidence for a beneficial effect of the tricyclic antidepressant nortriptyline, however, the RCTs for this medication lack sufficient validity, and reports on side effects are contradictory.

Antidepressive Agents↗
PubMed2002

Neurogenic heterotopic ossification in spinal cord injury.

Neurogenic heterotopic ossification (NHO) is a frequent complication in spinal cord injury (SCI) that is often difficult to treat. This review emphasizes the incidence, risk factors and clinical signs of NHO in SCI patients. Although the exact pathophysiology underlying NHO in neurologic patients is not yet understood, different pathogenic mechanisms have been proposed in the literature. A selection of the most important theories will be given and discussed. Moreover the different diagnostic, therapeutic, and preventive methods currently used in NHO management after SCI will be reviewed.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2002

Treatment of upper extremity spasticity in stroke patients by focal neuronal or neuromuscular blockade: a systematic review of the literature.

Studies published from January 1966 until October 2000 on the clinical effects of focal neuronal and neuromuscular blockade in post stroke upper limb spasticity were identified. Twelve studies were included and evaluated on 13 methodological criteria. Ten studies on Botulinum toxin type A (BTX-A) treatment were found (of which 4 were randomised controlled trials (RCTs) and 6 were uncontrolled observational studies) as well as one uncontrolled observational study on phenol blockade of the subscapular muscle and one on alcohol blockade of the musculocutaneus nerve. The homogeneity of the patient groups with regard to diagnosis and their comparability with regard to functional prognosis and other sources of bias were generally unsatisfactory. Only two RCTs met predetermined criteria of minimal validity. There is evidence of effectiveness of BTX-A treatment on reducing muscle tone (varying between 0.8 and 2.0 points on the modified Ashworth scale) and improving passive range of motion at all arm-hand levels in chronic stroke patients for approximately 3-4 months. There is also preliminary evidence of a synergistic effect of concomitant electrostimulation. Taking into account a critical maximum dose of 100 MU Botox" (300-500 MU Dysport) for preserving active finger flexion, BTX-A treatment seems to be a safe focal spasmolytic treatment. Effectiveness of BTX-A treatment on improving functional abilities could not be convincingly demonstrated, although two subgroups may be identified that might specifically benefit at a functional level: (1) patients with mild spasticity and a potential for voluntary extensor activity and (2) patients with severe spasticity suffering from problems with positioning and taking care of the affected arm and hand. Larger controlled studies are needed to compare the effectiveness of BTX-A with other focal spasmolytic techniques paying special attention to individual goal assessment, the (duration of) functional benefits, co-treatment and aftercare, side-effects and cost-effectiveness.

Botulinum Toxins↗