Gail A. Eskes

Fatigue associated with stroke and other neurologic conditions: Implications for stroke rehabilitation.

OBJECTIVES To examine the general phenomenon of fatigue in stroke and other neurologic disorders and to review what is currently known about its occurrence, including its frequency, duration, severity, and associated factors, to develop a strategy for treatment. DATA SOURCES Computerized databases (eg, PubMed, PsycInfo, Science Citation Index, Ovid EMBASE, Ovid MEDLINE) searched from inception to May 2002. Additional references were identified from bibliographies of pertinent articles and books. STUDY SELECTION Over 1000 articles were identified as relevant to fatigue experienced by patients with neurologic or nonneurologic disorders. Articles on fatigue in stroke and neurologic disorders, mechanisms, and/or treatment were selected for inclusion. DATA EXTRACTION Authors reviewed the articles and assessed the purpose, study design, and conclusions for validity and relevance to the topic of fatigue in stroke. DATA SYNTHESIS Fatigue is a common complaint among patients with neurologic disorders including stroke. Few studies have documented the high frequency of fatigue in poststroke patients and its negative impact on daily functioning and quality of life. Little is known about associated factors or about therapeutic strategies that may be used to alleviate it. Examination of fatigue in other neurologic populations suggests common characteristics and associated factors that may be useful in the development of potential therapeutic strategies. Pharmacologic and nonpharmacologic therapeutic interventions, such as stimulants, amantadine, or sleep and stress-management education, have been used with some success in neurologic and other patient populations (eg, multiple sclerosis, human immunodeficiency virus, acquired immune deficiency syndrome, cancer), but evidence of effectiveness based on randomized clinical trials is rare. CONCLUSIONS Poststroke fatigue is common. Therapeutic strategies have been used to treat fatigue in other patient populations, but it is unclear whether these will be beneficial to poststroke patients. Frequency, severity, duration, impact, predisposing factors, and causes of poststroke fatigue, as well as the development of effective treatment, require further research. Criteria for assessment of fatigue and potential therapeutic interventions are outlined as a first step for stimulating further research.

Appraising the ANT: Psychometric and theoretical considerations of the Attention Network Test

OBJECTIVE The Attention Network Test (ANT) is a tool used to assess the efficiency of the 3 attention networks-alerting, orienting, and executive control. The ANT has become popular in the neuropsychological literature since its first description in 2002, with some form of the task currently appearing in no less than 65 original research papers. Although several general reviews of the ANT exist, none provide an analysis of its psychometric properties. METHOD Data from 15 unique studies were collected, resulting in a large sample (N = 1,129) of healthy individuals. Split-half reliability, variance structure, distribution shape, and independence of measurement of the 3 attention network scores were analyzed, considering both reaction time and accuracy as dependent variables. RESULTS Split-half reliabilities of reaction time based attention network scores were low for alerting (rweighted = .20, CI 95%weighted [.14, .27], Spearman-Brown r = .38) and orienting (rweighted = .32, CI 95%weighted [.26, .38], Spearman-Brown r = .55), and moderate high for executive control (rweighted = .65, CI 95%weighted [.61, .71], Spearman-Brown r = .81). Analysis of the variance structure of the ANT indicated that power to find significant effects was variable across networks and dependent on the statistical analysis being used. Both analysis of variance (significant interaction observed in 100% of 15 studies) and correlational analyses (multiple-significant inter-network correlations observed) suggest that the networks measured by the ANT are not independent. CONCLUSIONS In the collection, analysis and interpretation of any test data, psychometric properties, such as those reported here for the ANT, must be carefully considered.

Developing a Measure of Sluggish Cognitive Tempo for Children: Content Validity, Factor Structure, and Reliability

Sluggish cognitive tempo (SCT) is a construct that some researchers believe may be extremely useful in understanding the inattentive subtype of attention-deficit/hyperactivity disorder, and may even help define a completely new disorder. However, the construct of SCT is as yet inadequately operationally or theoretically defined. The authors took the first steps toward developing an empirically supported measure of SCT in children. In Study 1, potential items to measure SCT were identified from a literature review, content validity of the items was evaluated by a group of experts, and a preliminary set of SCT items were selected. In Study 2, ratings completed by parents and teachers of 335 children (ages 4-13) were used to further develop and evaluate the SCT items by computing factor analyses, item-level analyses, reliability analyses, and preliminary validity analyses. The final SCT scale (14 items) produced a total scale score and 3 subscale scores: Slow, Sleepy, and Daydreamer. These scales were constructed with good content validity and were found to have strong reliability. Future directions include replication, extension into a clinical population, and further examination of validity.

Comprehension of concrete and abstract words in autistic children

This study employed the Stroop paradigm to examine comprehension of single words in autistic children. The words of interest varied along a concrete-abstract dimension. In the Stroop paradigm, subjects are asked to name the color of ink in which color words are printed. Comprehension is indexed by the degree to which the automatic processing of words interferes with the colornaming task. For both concrete and abstract words, autistic children showed the same degree of interference as readingmatched controls. The findings corroborate and extend previous work suggesting that autistic children understand, and by implication, can mentally represent, at least some word meanings.

Assessment of working memory abilities using an event-related brain potential (ERP)-compatible digit span backward task ☆

OBJECTIVE This study investigated the effectiveness of an ERP-compatible Digit Span Backward (ERP-DB) task to determine working memory abilities in healthy participants. METHODS Participants were administered both the standard digit span backward and ERP-DB tasks. The ERP-DB task was divided into two sections, consisting of 2, 4, 6 and 8 (Group 1) and 3, 5, and 7 (Group 2) set sizes. A set of digits was aurally presented, followed by a second set that either corresponded to the reverse order of the first set (correct condition) or had one digit in the sequence replaced by an incorrect digit (incorrect condition). RESULTS Two posterior positive components were found to distinguish the two conditions; an earlier positive component (P200/P300) was elicited in the correct condition, whereas a comparatively robust and prolonged positive slow wave (PSW) was elicited in the incorrect condition. Furthermore, the PSW and the difference in PSW amplitude between incorrect and correct conditions (dPSW) dissipated as working memory load increased and were related to working memory capacity. CONCLUSIONS The PSW, dPSW and P200/P300 components were found to be associated with working memory abilities and may have the potential to act as neurophysiological markers for the assessment of working memory capacity. SIGNIFICANCE This research lends support for the utility of the ERP-DB task as a means of assessing working memory abilities, which may have implications for testing patients with expressive communication impairments.

The cognitive neuropsychology of attention: A frontal lobe perspective.

Abstract Recent research on the cognitive sequelae of focal frontal damage has significantly advanced our understanding of the role of the frontal lobes in attentional function. Although early studies using traditional psychometric tests had suggested that attention was not grossly impaired in patients with focal frontal lobe lesions, more recent studies have demonstrated deficits in dissociable capacities such as the direction of extrapersonal attention, selective attention, inhibition, orienting responses, habituation, and sustained attention. Behaviourally, these deficits may be manifested as distractibility, neglect, and impulsivity. There is some suggestion of localisation of attentional processes within the frontal cortex, with the right frontal lobe being particularly implicated in the mediation of sustained and directed attention. However, there does not yet appear to be any conclusive evidence in the focal frontal literature concerning the localisation of other attentional processes. Prescription...

Cognitive-Motor Interference During Functional Mobility After Stroke: State of the Science and Implications for Future Research

Cognitive-motor interference (CMI) is evident when simultaneous performance of a cognitive task and a motor task results in deterioration in performance in one or both of the tasks, relative to performance of each task separately. The purpose of this review is to present a framework for categorizing patterns of CMI and to examine the specific patterns of CMI evident in published studies comparing single-task and dual-task performance of cognitive and motor tasks during gait and balance activities after stroke. We also examine the literature for associations between patterns of CMI and a history of falls, as well as evidence for the effects of rehabilitation on CMI after stroke. Overall, this review suggests that during gait activities with an added cognitive task, people with stroke are likely to demonstrate significant decrements in motor performance only (cognitive-related motor interference), or decrements in both motor and cognitive performance (mutual interference). In contrast, patterns of CMI were variable among studies examining balance activities. Comparing people poststroke with and without a history of falls, patterns and magnitude of CMI were similar for fallers and nonfallers. Longitudinal studies suggest that conventional rehabilitation has minimal effects on CMI during gait or balance activities. However, early-phase pilot studies suggest that dual-task interventions may reduce CMI during gait performance in community-dwelling stroke survivors. It is our hope that this innovative and critical examination of the existing literature will highlight the limitations in current experimental designs and inform improvements in the design and reporting of dual-task studies in stroke.

Executive function in patients with obstructive sleep apnea treated with continuous positive airway pressure

Obstructive sleep apnea (OSA) is characterized by disrupted breathing and hypoxemia during sleep, daytime sleepiness, and changes in cognition and mood. One important question is regarding the reversibility of cognitive deficits after treatment with continuous positive airway pressure (CPAP). Here, we report the outcomes of CPAP treatment as measured by tests of attention and executive function. Thirty-seven individuals with moderate to severe OSA and compliant on CPAP treatment were studied with working memory tasks, neuropsychological testing, and overnight polysomnographic sleep study and compared to 27 healthy controls. CPAP improved the respiratory disturbance index, minimum and mean oxygen saturation (SpO2), subjective sleep quality, and daytime sleepiness ratings compared to pre-treatment values. In terms of current neurocognitive function, treated individuals with OSA performed at a comparable level to controls on basic working memory storage functions but still showed a significant reduction on tests of working memory requiring the central executive. The OSA group also performed worse on neuropsychological measures of complex attention, executive function, and psychomotor speed. While CPAP is an effective treatment for OSA in terms of ameliorating breathing disruption and oxygen desaturation during sleep, as well as daytime sleepiness, some cognitive deficits may be more resistant to treatment.

Predicting functional outcome after stroke by modelling baseline clinical and CT variables

BACKGROUND we aimed to assess whether the performance of stroke outcome models comprising simple clinical variables could be improved by the addition of more complex clinical variables and information from the first computed tomography (CT) scan. METHODS 538 consecutive acute ischaemic and haemorrhagic stroke patients were enrolled in a Stroke Outcome Study between 2001 and 2002. Independent survival (modified Rankin scale <or=2) was assessed at 6 months. Models based on clinical and radiological variables from the first assessment were developed using multivariate logistic regression analysis. RESULTS three models were developed (I-III). Model I included age, pre-stroke independence, arm power and a stroke severity score (area under a receiver operating characteristic curve, AUC = 0.882) but performed no better than Model II, which comprised age, pre-stroke independence, normal verbal component of the Glasgow coma score, arm power and being able to walk without assistance (AUC 0.876). Model III, including two radiological variables and clinical variables, was not statistically superior to model II (AUC 0.901, P = 0.12). Model II was externally validated in two independent datasets (AUCs of 0.773 and 0.787). CONCLUSION this study demonstrates an externally validated stroke outcome prediction model using simple clinical variables. Outcome prediction was not significantly improved with CT-derived radiological variables or more complex clinical variables.

Dual effects of body-weight supported treadmill training on cardiovascular fitness and walking ability early after stroke: a randomized controlled trial.

Background. Body-weight-supported treadmill training (BWSTT) to train both fitness and ambulation has not been investigated. Objective. To compare the effectiveness of BWSTT to dose-equivalent usual care (UC) in improving cardiovascular fitness and walking early after stroke. Methods. Participants were randomly assigned to 1 of 2 interventions: BWSTT + UC or UC. All individuals participated in 60-minute physiotherapy sessions 5 times weekly as inpatients for 6 weeks and 3 times weekly as outpatients for another 6 weeks. Baseline, posttraining, 6-, and 12-month follow-up outcome measures were as follows: primary, fitness (peak oxygen consumption, VO2peak) and walking ability (6-Minute Walk Test [6MWT] and 10-m walk); secondary, Berg Balance Scale (BBS) and motor impairment (Chedoke-McMaster Stages of Recovery [CMSR] Leg and Foot). Results. In all, 50 individuals (mean age, 60 ± 14 years; mean event-to-randomization, 23 ± 5 days; 29 men) participated. No adverse events occurred. BWSTT improved VO2peak by 30%, which was significantly greater than the 8% improvement observed for UC (P = .004 between groups). Similarly, there were significant Time × Group interactions for 6MWT and CMSR Foot, with BWSTT outperforming UC for gains in distance (P = .15; 48% vs 19%, respectively) and stage (P = .01; 1.0 vs 0.3, respectively). No group effect was seen for 10-m walk speed, BBS, or CMSR Leg, with both groups demonstrating significant gains. In general, gains observed were preserved for 12 months. Conclusions. BWSTT elicits greater improvements in cardiovascular fitness and walking endurance than UC in the subacute poststroke period. These gains are largely sustained for 1 year.