Cognitive fatigue during a test requiring sustained attention: a pilot study

Effect of estrogen and testosterone replacement therapy on cognitive fatigue

Both estrogen and testosterone insufficiency has been associated with reduced psychological well-being including fatigue. However, hormonal replacement studies on fatigue are rare. Therefore, we wanted to study the effect of testosterone and estrogen replacement therapy on cognitive fatigue and the relation between sex hormone levels and cognitive fatigue in oophorectomized women. Fifty women with surgically induced menopause (mean age: 54.0 ± 2.9 years) were randomly assigned to treatment with estradiol valerate in combination with testosterone undecanoate or placebo for 24 weeks in a double-blind cross-over study. Neuropsychological tests and questionnaires were used to assess cognitive fatigue and psychological well-being. Cognitive fatigue was significantly associated to poor self-rated health and higher body mass index but not to general psychological well-being or sex hormone levels. Treatment with testosterone + estrogen had no significant effect on cognitive fatigue but the results indicated a curvilinear relation for hormonal levels. The estrogen/testosterone ratio was more related to functions rather than high or low hormone levels per se. We found that cognitive fatigue is frequent in oophorectomized women and negatively associated to self-perceived health and positively associated to BMI. A well-balanced ratio between estrogen and testosterone levels may be important for cognitive fatigue.

The effects of heat stress on cognition in persons with multiple sclerosis

Background: Heat sensitivity and cognitive deficits are typical manifestations of multiple sclerosis (MS). Although cognitive deficits are quite well characterized, practically no data exist on the effects of heat on cognitive performances in MS.

Objective: To assess the effects of short-term heat stress on cognitive functioning in subjects with MS.

Methods: A total of 23 heat-sensitive MS and 19 healthy control (HC) subjects participated. Moderate heat exposure took place in a Finnish sauna. Cognitive functioning was measured with tests of sustained attention and processing speed, the Paced Auditory Serial Addition Test (PASAT 3” and 2”) and the computerized visual vigilance test, before, during and after heat exposure.

Results: During the heat exposure, the core body temperature of the MS group rose significantly more ( p = 0.002) than that of the HC group. The heat stress worsened the performance of the MS group in the PASAT 3” ( p = 0.025) but not in the other cognitive measures. The performance in the PASAT 3” was reversed almost to the baseline level only 1- h after the heat exposure.

Conclusions: A significant increase in core body temperature during heat stress is associated with a mild and reversible worsening of the PASAT 3” performance, while visual vigilance performance seems to remain almost unaffected.

The effects of rivastigmine on processing speed and brain activation in patients with multiple sclerosis and subjective cognitive fatigue

Background: Cognitive decline and fatigue are typical in multiple sclerosis (MS). However, there is no official medication for either of these symptoms.

Objective: The purpose of this study was to estimate the effects of a single dose of rivastigmine on processing speed and associated brain activity in patients with MS and subjective cognitive fatigue.

Methods: Fifteen patients with MS and subjective cognitive fatigue and 13 healthy controls (HCs) matched for age, gender and education performed a neuropsychological assessment and functional (f)MRI. A modified version of the Paced Visual Serial Addition Test (mPVSAT) was used as the behavioural task during fMRIs. After the first scanning session, both groups were randomly divided into two subgroups receiving either rivastigmine or placebo. A single dose of rivastigmine or placebo was administrated double-blindly and 2.5 hours later the scanning was repeated.

Results: At baseline, the patients with MS showed slower processing speed in mPVSAT compared with the HCs. They also demonstrated stronger bilateral frontal activation after sustained cognitive effort than the HCs. Performance improvement and a further activation increase in the left anterior frontal cortex and additional activation in the right cerebellum were observed in patients who received rivastigmine but not in patients on placebo, or in HCs with placebo or rivastigmine.

Conclusion: These preliminary findings suggest that rivastigmine may improve cognitive processing speed by enhancing compensatory brain activation in patients with MS.

Cognition in multiple sclerosis

PURPOSE OF REVIEW

A broad overview of cognition in multiple sclerosis (MS) is provided, taking account of its impact on the lives of patients, how cognitive impairment relates to disease and magnetic resonance variables, which cognitive domains are most vulnerable, the influence of depression and fatigue and what treatment options are available.

RECENT FINDINGS

The current focus is on cognitive reserve, which seems to offer some protection from the cognitive impact of MS. There is also considerable momentum with new MRI techniques and growing interest in PET studies.

SUMMARY

Cognition in MS is a priority for patients. Although understanding of the natural history of MS cognitive deficits is reasonably well understood, treatment options require further work before precise recommendations can be made on an individual basis.

HAGIL (Hamburg Vigil Study): a randomized placebo-controlled double-blind study with modafinil for treatment of fatigue in patients with multiple sclerosis

Objective: To reassess the effect of modafinil, a wakefulness-promoting artificial psychostimulant, on fatigue and neuropsychological measures in patients with multiple sclerosis.

Methods: Multiple sclerosis (MS) patients with a baseline score of ≥4 on the Fatigue Severity Scale (FSS) and an Expanded Disability Status Scale score <7 were eligible for the 8-week randomized, double-blind, placebo-controlled study. Modafinil was dosed up to 200 mg/day within 1 week. Assessments were performed at baseline and after 4 and 8 weeks. The primary outcome parameter was the mean change of the FSS mean score. Secondary outcome variables were other questionnaires covering fatigue, daytime sleepiness and sleep quality. Cognitive impairment was assessed by the oral version of the Symbol Digit Modalities Test (SDMT) and the Paced Auditory Serial Addition Test (PASAT).

Results: The study included 121 MS patients. Dropout rate was 9%. Both treatment groups showed improvements through time. While mean FSS at 8 weeks showed a trend difference between groups in the intention-to-treat analysis, the primary endpoint was not met. Assessment of cognitive impairment by SDMT and PASAT showed contradictory results. All other secondary endpoints were not met. There was no major safety concern.

Conclusions: In general, the study does not support modafinil as an effective treatment for MS fatigue. However, the study shows the need for new study designs and endpoints in MS fatigue studies.

Cognitive fatigue defined in the context of attention networks

We examined the effect of cognitive fatigue on the Attention Networks Test (ANT). Participants were 228 non-demented older adults. Cognitive fatigue was operationally defined as decline in alerting, orienting, and executive attention performance over the course of the ANT. Anchored in a theoretical model implicating the frontal basal ganglia circuitry as the core substrate of fatigue, we hypothesized that cognitive fatigue would be observed only in executive attention. Consistent with our prediction, significant cognitive fatigue effect was observed in executive attention but not in alerting or orienting. In contrast, orienting improved over the course of the ANT and alerting showed a trend, though insignificant, that was consistent with learning. Cognitive fatigue is conceptualized as an executive failure to maintain and optimize performance over acute but sustained cognitive effort resulting in performance that is lower and more variable than the individual's optimal ability.

Effects of long-term resistance training and simultaneous electro-stimulation on muscle strength and functional mobility in multiple sclerosis

Background: Resistance training studies in multiple sclerosis (MS) often use short intervention periods. Furthermore, training efficiency could be optimized by unilateral training and/or electrical stimulation.

Objective: To examine the effect(s) of unilateral long-term (20 weeks) standardized resistance training with and without simultaneous electro-stimulation on leg muscle strength and overall functional mobility.

Methods: A randomized controlled trial involving 36 persons with MS. At baseline (PRE) and after 10 (MID) and 20 (POST) weeks of standardized (ACSM) light to moderately intense unilateral leg resistance training (RESO, n = 11) only or resistance training with simultaneous electro-stimulation (RESE, n = 11, 100 Hz, biphasic symmetrical wave, 400 µs), maximal isometric strength of the knee extensors and flexors (45°, 90° knee angle) and dynamic (60–180°/s) knee-extensor strength was measured and compared with a control group (CON, n = 14). Functional mobility was evaluated using the Timed Get Up and Go, Timed 25 Foot Walk, Two-Minute Walk Test, Functional Reach and Rivermead Mobility Index.

Results: Maximal isometric knee extensor (90°, MID: +10 ± 3%, POST: +10 ± 4%) in RESO and knee flexor (45°, POST: +7 ± 4%; 90°, POST: +9 ± 5%) in RESE strength increased ( p < 0.05) compared with CON but RESO and RESE did not differ. Also, impaired legs responded positively to resistance training (unilateral leg strength analysis) and functional reaching increased significantly in RESO (+18%) compared with CON. Dynamic muscle strength and the remaining functional mobility tests did not change.

Conclusion: Long-term light to moderately intense resistance training improves muscle strength in persons with MS but simultaneous electro-stimulation does not further improve training outcome.

Central and peripheral fatigue: exemplified by multiple sclerosis and myasthenia gravis

Fatigue is a feature of several chronic diseases of the central and peripheral nervous system. The pathophysiology of central fatigue is complex and often not well-defined. In contrast, peripheral fatigue is more objectively defined and measured. Fatigue can be part of the primary disease process, but there are often contributions from comorbid factors such as depression, sleep disturbance, medication, or deconditioning. Multiple sclerosis (MS) offers an example of central fatigue. More than 40% of MS patients complain of fatigue. Validated questionnaires are used to assess fatigue severity and comorbid factors. Although fatigue is believed to be a primary process in MS, depression and sleep disturbance are often comorbid problems. Magnetic resonance imaging (MRI), positron emission tomography, and functional MRI studies suggest that fatigue is related to gray matter disease, particularly of the cerebral cortex, but also of the thalamus and caudate. Disruption of impulse propagation from demyelination is also a likely factor. It is uncertain if pro-inflammatory cytokines have a specific effect on the genesis of MS fatigue. Several medications have been reported to alleviate fatigue in MS, but controlled studies show contradictory results. Treatment of depression and sleep disturbance, use of exercise programs and rehabilitation therapies as well as treatment of other comorbid conditions is necessary for optimal alleviation of fatigue. Myasthenia gravis (MG) patients exhibit peripheral fatigue. In contrast to MS, the mechanism of weakness and fatigue in MG is well-defined. Antibodies to the postsynaptic acetylcholine receptor at the myoneural junction cause diminution of the force of muscle contractions. This leads to a feeling of fatigue. MG treatments increase the availability of acetylcholine and reduce antibody formation. Evaluation for comorbid conditions, especially thymoma and hyperthyroidism, are mandatory in patients with MG.

Assessment and rehabilitation of cognitive impairment in multiple sclerosis

Patients with multiple sclerosis (MS) have a substantial risk of cognitive dysfunction, even in the earliest stages of the disease, where there is minimum physical disability. Despite the high prevalence rates and the significant impact of cognitive dysfunction on quality of life in this population, cognitive functions are not routinely assessed due to the high cost and time consumption. This article provides an overview of the current state of knowledge related to cognition in MS and on the optimal approach to neuropsychological assessment of this population. It then focuses on the pharmacological and other treatment options available for MS patients with, or at risk for developing, cognitive impairment. The available immune-modulating agents may reduce the development of new lesions and therefore prevent or minimize the progression of cognitive decline. However, there is currently insufficient evidence concerning the efficiency of symptomatic treatment in MS. There is also currently no optimal non-pharmacological treatment strategy for cognitive decline in MS, as the studies published to date report heterogeneous results. Nevertheless, non-pharmacological treatments such as cognitive rehabilitation may benefit some MS patients. As cognition is increasingly recognized as a major feature of MS, its assessment and rehabilitation will become a greater priority.

Quality of life among children with velocardiofacial syndrome

OBJECTIVE

To explore the health-related quality of life (QoL) among children with velocardiofacial syndrome (VCFS) and to compare QoL by gender and with samples of chronically ill and healthy children.

DESIGN AND SETTING

Cross-sectional design, comparing data obtained from a survey of parents of children with VCFS to previously published data from comparison groups of children who are healthy or who have other chronic conditions.

PARTICIPANTS

Parents of 45 children aged 2 to 18 years with VCFS participated in this study. Results were compared with published data on the same measures from samples of parents of healthy children (n = 10,343) and children with a variety of chronic conditions (n = 683).

MAIN OUTCOME MEASURES

Quality of life, including fatigue, was measured using the PedsQL(TM) Measurement Model. Strengths were assessed by parent report from a list of character traits developed from the Values in Action Classification System.

RESULTS

Quality of life was lower across all domains compared with healthy children. Boys with VCFS scored significantly lower than girls on school functioning (p < .05) and cognitive fatigue (p < .01). Compared with children with chronic conditions, children with VCFS scored lower on emotional (p < .01), social (p < .01), and school functioning (p < .001) but not on physical health. Parents described their children's strengths as humor, caring, kindness, persistence, and enthusiasm.

CONCLUSIONS

Quality of life among children with VCFS is characterized by significant challenges in the cognitive, social, and emotional domains. These children have strengths that may be useful in coping with the daily challenges of this condition.

The neural correlates of cognitive fatigue in traumatic brain injury using functional MRI

PRIMARY OBJECTIVE

The present study used fMRI (functional magnetic resonance imaging) to objectively assess cognitive fatigue in persons with traumatic brain injury (TBI). It was hypothesized that while performing a cognitive task, TBI participants would show increased brain activity over time, indicative of increased cerebral 'effort' which might manifest as the subjective feeling of cognitive fatigue.

METHODS AND PROCEDURES

Functional MRI was used to track brain activity across time while 11 TBI patients with moderate-severe injury and 11 age-matched healthy controls (HCs) performed a modified Symbol Digit Modalities Task (mSDMT). Cognitive fatigue was operationally defined as a relative increase in cerebral activation across time compared to that seen in HCs. ROIs were derived from the Chauduri and Behan model of cognitive fatigue.

MAIN OUTCOMES AND RESULTS

While performing the mSDMT, participants with a TBI showed increased activity, while HCs subsequently showed decreased activity in several regions including the middle frontal gyrus, superior parietal cortex, basal ganglia and anterior cingulate.

CONCLUSIONS

Increased brain activity exhibited by participants with a TBI might represent increased cerebral effort which may be manifested as cognitive fatigue. Functional MRI appears to be a potentially useful tool for understanding the neural mechanisms associated with cognitive fatigue in TBI.

Poststroke fatigue--a review

Although fatigue is a common complaint after stroke, relatively little is known about how poststroke fatigue is experienced and what its related factors are. An in-depth understanding is necessary to develop effective and patient-centered poststroke rehabilitation programs. This review was undertaken to provide a comprehensive synthesis of knowledge from the literature concerning the description, definition, and measurement of fatigue and its relationship to sociodemographic and clinical factors. A search in PubMed, CINAHL, EMBASE, and PsychInfo was performed using "stroke" or "cerebrovascular accident" as medical subject headings in combination with "fatigue" as a key word. Descriptions of fatigue revealed multiple dimensions of the phenomenon. Although no specific theoretical definition of fatigue as a poststroke condition was found, a case definition has recently been published to be used as a tool to determine the presence of fatigue in poststroke patients. Poststroke fatigue is most frequently measured by using the general fatigue scales such as the Fatigue Severity Scale and a Fatigue Visual Analogue Scale, as there is no scale developed to measure poststroke fatigue specifically. Age, sex, living conditions, and personality were associated with poststroke fatigue, albeit with some conflicting findings. Conflicting results also were found in the relationships between fatigue and stroke-related characteristics such as stroke location/type, the number of strokes, and neurological deficits. There is an indication that prestroke and poststroke fatigue are related. Possible antecedent components identified are personal factors, biomarkers, stroke characteristics, prestroke fatigue, and comorbidity. As knowledge regarding poststroke fatigue remains limited, there is a need to continue empirical research with various theoretical orientations.

Subjective fatigue is not associated with cognitive impairment in multiple sclerosis: cross-sectional and longitudinal analysis

Background

Studies in multiple sclerosis (MS) report conflicting conclusions regarding fatigue and cognition, which may partly be due to the use of small sample sizes and frequent reliance on a cross-sectional approach.

Objective

The ability to distinguish between these two disabling symptoms is necessary in order to properly assess and treat MS patients.

Methods

In a retrospective analysis, we assessed the correlation between fatigue and neuropsychological (NP) testing using a cross-sectional ( n = 465) and longitudinal approach ( n = 69). Cognition was measured using a comprehensive battery called the Minimal Assessment of Cognitive Function in MS (MACFIMS), and fatigue was measured with the Fatigue Severity Scale (FSS). FSS scores were categorized as normal (≤4.0), borderline fatigue (4 < FSS < 5.0), and fatigued (≥5.0). Repeat assessments ( n = 69) were categorized as improved or worsened by a change in FSS of either 0.5 or 1.0.

Results

MS patients had significantly higher FSS scores than normal controls ( P < 0.001). No correlation was found between FSS and NP scores in either cross-sectional or longitudinal analyses. Fatigue was moderately correlated with depression, assessed using the Beck Depression Inventory Fast Screen (BDIFS) ( r = 0.44, P < 0.001). Longitudinally, there was a medium correlation between change in FSS and BDIFS ( r = 0.34, P = 0.001), but no significant differences on NP scores using either definition of change.

Conclusion

We conclude that self-reported fatigue, while correlated with self-reported depression, is not significantly related to cognitive capacity in MS.

[Cognitive impairment]

Cognitive impairment is common in multiple sclerosis (MS), occurring at all stages of the disease, even at the earliest, and can be a major source of disability, social impairment, and impoverished quality of life. Cognitive dysfunction is mainly focused on working memory, conceptual reasoning, verbal fluency, speed of information processing, attention and executive function. Measures of information-processing speed appear to be the most robust and sensitive markers of cognitive impairment in MS patients. Cognitive testing in MS patients is complex and cognitive screening tests are time- and cost-saving test instruments. A comprehensive and sensitive cognitive test procedure should be administered to detect cognitive dysfunction, and recent studies demonstrate that single, predominantly speed-related cognitive tests may be superior to extensive and time-consuming test batteries in screening cognitive decline. Additional clinical factors, including disease course, fatigue, and affective disturbance, can impact the degree of MS-related cognitive impairment. Despite weak correlation with disease duration and physical disability status, the degree of cognitive impairment in MS has been related to the extent of topographically specific neuronal tissue damage and loss. Numerous studies have applied conventional and quantitative magnetic resonance imaging (MRI) techniques to correlate the profile and degree of cognitive impairment with various MRI-detectable abnormalities. The burden of MRI-visible lesions does not fully account for the degree of MS-related cognitive impairment. Nonconventional MRI findings suggest the extent of subtle tissue damage in normal-appearing white and grey matter to correlate best with the severity of cognitive impairment in MS patients. Structural MRI approaches have recently been extended by functional MRI studies scrutinizing the brain's ability for adaptive functional reorganization in the presence of widespread tissue damage. Cognitive impairment in MS seems to be not simply the result of tissue destruction, but also a balance between tissue destruction, tissue repair, and adaptive functional reorganization. These findings highlight the need to screen for cognitive deficits in MS patients to conduct potential cognitive rehabilitation intervention.

The psychology of fatigue in patients with multiple sclerosis: a review

Fatigue is a frequent and disabling symptom in patients with multiple sclerosis (MS), but it is difficult to define and measure. Today, MS-related fatigue is not fully understood, and evidence related to explanatory pathophysiological factors are conflicting. Here, we evaluate the contribution of psychological factors to MS-related fatigue. Insight into the possible underlying psychological mechanisms might help us to develop adequate psychological interventions and to improve the overall management of fatigue. Conceptual issues and the relationships between MS-related fatigue and mood, anxiety, cognition, personality, and cognitive-behavioral factors are discussed, and the implications for clinical practice and research are presented.

Neural correlates of cognitive fatigue in multiple sclerosis using functional MRI

Although fatigue is one of the major symptoms of persons with multiple sclerosis (MS), the behavioral and neural correlates are poorly understood. The present study utilized a novel approach to cognitive fatigue examining objective behavioral performance while simultaneously monitoring brain activity using fMRI. Fifteen persons with MS and 15 healthy controls were given 4 trials of a behavioral task assessing processing speed (mSDMT) during fMRI acquisition. It was hypothesized that individuals with MS would show an abnormal pattern of activity across time in specific brain areas previously hypothesized to subserve fatigue [Chaudhuri A, Behan PO. Fatigue and basal ganglia. J Neurol Sci 2000;179:34-42]. Specifically, it was hypothesized that persons with MS would show a greater increase in cerebral activation across time during behavioral performance than that seen in healthy controls, which was interpreted as fatigue. No difference in performance accuracy on the mSDMT was observed, although the MS group was significantly slower than controls. Behavioral alterations indicative of fatigue in the MS group were associated with increased activation in the basal ganglia, frontal areas including superior, medial, middle and inferior regions, parietal regions (precuneus and cuneus), thalamus and the occipital lobes. These data provide direct support for the Chaudhuri and Behan model of "central" fatigue which hypothesizes a specific role of the "non-motor" functions of the basal ganglia.

Within-session practice effect on paced auditory serial addition test in multiple sclerosis

The paced auditory serial addition test (PASAT) is increasingly used in multiple sclerosis (MS) studies. Since these studies rely on repeated assessments with relatively short inter-test intervals, practice effects can be a confounding factor. We examined intra-session PASAT practice effects in 70 relapsing remitting (RR) and 40 secondary progressive (SP) patients. The average number of correct answers increased from 39.6 ± 11.7 in the first PASAT run to 43.8 ± 11.4 in the second run for the RR group, and from 39.1 ± 11.6 to 41.8 ± 13.3 in the SP group. PASAT scores showed a consistent decrease when comparing the second half of each test to the first half for both patient groups, and for both runs. Items for which the answer was a number greater than 9 had the same discrimination ability as other test items, but were significantly more difficult. A simulation of `single-button' responses supported the use of the simplified scoring method which is currently used in fMRI studies. Our results demonstrate a within-session PASAT practice effect in MS, as well as a fatigability effect for both patient groups.

Fatigue in multiple sclerosis presenting as acute relapse: subjective and objective assessment

We report on a patient with multiple sclerosis (MS) who presented with fatigue as the only manifestation of an acute MS relapse. Fatigue was assessed by the `Würzburg Fatigue Inventory in MS (WEIMuS)' scale and confirmed by neuropsychological testing of attention. After high-dose corticosteroid therapy, subjective symptoms were completely abolished. The improvement was corroborated by both, the WEIMuS score and neuropsychological testing. MS-related fatigue may be the only symptom of an acute MS relapse, and neuropsychological methods may be used to objectively assess and follow the time course of this common and disabling symptom. Multiple Sclerosis 2008; 14: 274—277. http://msj.sagepub.com

Qualitative and quantitative assessment of fatigue in multiple sclerosis (MS)

It was the aim of the present study to develop a synoptic multidimensional test system for assessment of fatigue in multiple sclerosis (MS) patients objectifying physical and mental fatigue as well as the subjective and objective standpoint in these two fatigue forms. Seventy nine patients with relapsing remitting multiple sclerosis (RRMS) and 51 age-matched healthy controls (H) were analysed by means of the physical fatigue test (hand dynamometer) and an objective mental fatigue test (vigilance test from the computerised Test Battery for Attentional Performance). Furthermore, subjective tiredness caused by test procedures, subjective persisting tiredness (Modified Fatigue Impact Scale; MFIS: physical and cognitive scale) and mood (Beck Depression Inventory; BDI-18) were analysed.MS patients differed significantly from the controls in their objective physical and mental performance under fatigue, as well as in their subjective estimation of tiredness. MS patients showed an inverse relationship between below-average objective performance and high subjective feeling of tiredness when compared to controls. Subjectively severely tired MS patients achieved clearly poorer performances on the hand dynamometer test and slightly poorer performances on the vigilance test when compared to subjectively rarely tired MS patients. Depressed MS patients estimated their subjective tiredness in the MFIS significantly higher than non-depressed MS patients, but attained the same objective performance. This set of standardised tests enables meaningful comparisons between objective fatigue performance and subjective fatigue estimations in the physical and mental sphere and considers the influence of depression. Depression affects the subjective tiredness but not the objective fatigue performance.

A shortened version of PASAT-3 is feasible

The Paced Auditory Serial Addition Test (PASAT), most used neuropsychological test in people with multiple sclerosis (pwMS), is available as PASAT-3 and more difficult PASAT-2. We determined PASAT performance in 105 pwMS and 105 matched controls and assessed the utility of a shortened PASAT-3 version. Qualitative and quantitative analyses were performed, the latter involving assessment of dyads (two consecutive correct responses) and singles (correct response between two omitted responses). Based on provisional results we then calculated the sensitivity of the first 20 items of PASAT-3 in relation to the full version. Mean PASAT-2 and 3 total score, dyads and singles differed significantly (P < or = 0.0002) in pwMS and controls, due to more omissions in pwMS, number and type of incorrect answers did not differ. Differences between pwMS and controls were highly significant for the first 50, 40, 30 and 20 responses of the PASAT-3. The sensitivity of the first 20 items of PASAT-3 was 87% (95% CI 0.70-1.00). PASAT-3 and PASAT-2 effectively discriminate pwMS from controls. Use of the first 20 items of PASAT-3 appears as a highly useful PASAT-3 version as it retains the discriminative value and sensitivity of the full version yet is quicker to administer and less demanding.

Fatigue in neuroimmunological diseases

Fatigue is a widespread symptom in numerous neuroimmunological diseases like multiple sclerosis (MS), myasthenia gravis, morbus Behcet, neurosarcoidosis, neuroborreliosis or immune vasculitis. This phenomenon is best investigated in MS. The complex mechanisms underlying fatigue in MS are still poorly understood; alterations in immune system activation, central nervous system dysregulation, impaired nerve conduction, and neuroendocrine dysregulation have to be considered. These immune and neural mechanisms may cause the initial symptoms of fatigue; however, the fatigue symptom may be exacerbated by secondary overlapping factors (e. g. depressive mood, sleep disturbances, unhealthy life style) which are likely associated with the feeling of fatigue. Wessely conceptualised four components of fatigue: behaviour (effects of fatigue), feeling (subjective experience), mechanisms, and context (e. g. environment, attitudes). So far most examinations have dealt with the first or the second component of the multidimensional construct fatigue, either concentrating on the behavioural aspect in the physical or in the cognitive sphere or on the subjective aspect. The Rostock Fatigue Study investigated two of the components: objective performance and subjective fatigue estimation in the cognitive and in the physical sphere. MS patients showed a reversed relationship between below-average objective performance in the cognitive and in the physical sphere and high subjective feeling of tiredness when compared to healthy individuals. The clinical management of fatigue should include an assessment of the various factors that can cause fatigue as well as a step-wise treatment approach that encompasses nonpharmacological approaches and pharmacological interventions.

The relationship between subjective fatigue and cognitive fatigue in advanced multiple sclerosis

The present study examined the cognitive performance and ratings of subjective fatigue in people with advanced MS and matched healthy control participants. A continuous n-back task, involving attention (0-back), was performed at the beginning and end of one testing session; a task involving working memory (1-back) was performed at the beginning and end of another testing session. Subjective fatigue was rated at regular intervals during each session. Overall, there was limited evidence of objective cognitive fatigue in the MS group, as assessed by the change in n-back performance during the sessions. The MS group did report a greater increase, than the control group, in the level of subjective fatigue during the 1-back testing session, but change in subjective fatigue did not correlate significantly with change in cognitive performance. The implications of these findings for our understanding of cognitive fatigue in MS are discussed.

A rapid screening tool for fatigue impact in multiple sclerosis

BACKGROUND

Fatigue is a common complaint in multiple sclerosis (MS) and often interferes with daily functioning. Both clinicians and researchers may need to detect high levels of fatigue impact using a time and effort efficient tool. This study evaluates the psychometric properties of a rapid screening instrument for fatigue impact in multiple sclerosis.

METHODS

Three visual analogue scales (VAS) for assessing the impact of fatigue were developed. Sixty two subjects with definite MS (mean age 52 +/- 10.5 years; 29 women) and 24 healthy controls (mean age 52 +/- 14 years; 13 women) completed all VAS scales (range 0-100), the Fatigue Severity Scale (FSS) (range 7-63), the Modified Fatigue Impact Scale (MFIS) (range 0-84) and the Guy's Neurological Disability Scale (GNDS) (range 0-5). All tests were repeated with an interval of maximum three days. To evaluate the reproducibility, intraclass correlations (ICC) were calculated, based on one-way analysis of variance for repeated measurements. Validity was considered by means of correlation coefficients. ROC analysis was used to determine the accuracy of the VAS scales.

RESULTS

The ICC of the VAS scales ranged from 0.68 to 0.69. VAS scales showed low to moderate correlation with FSS, MFIS and GNDS (Kendall's tau 0.23-0.45) and were not related with physical or cognitive performance, or with depression. All VAS scales were able to discriminate between subjects with MS and controls. Twenty five subjects with MS had a Fatigue Severity Scale score of 36 or more and were classified into the "fatigue" group. ROC analysis showed that VAS_1 is most useful to classify subjects in the "fatigue" group. A cut-off value of VAS_1 of 59 displayed 76% sensitivity and 72% specificity. When using the MFIS score of 40 or more to classify the groups, VAS_1 remained the strongest tool, with 81% sensitivity and 77% specificity at a cut-off value of 59.

CONCLUSION

The VAS for the impact of fatigue on daily life (VAS_1) is a moderately reliable, though valid and useful tool to screen rapidly for fatigue impact in multiple sclerosis. A cut-off value of 59 satisfactorily classifies individuals having severe fatigue with a high impact on daily life. In clinical practice, a more comprehensive assessment of fatigue and the impact on daily life is recommended.

Cognitive impairment and neurophysiological correlates in MS

Cognitive impairment in multiple sclerosis (MS) has received considerable interest over the last decades. Heterogeneous patterns of cognitive dysfunction have been reported in literature in relation to the subtype of the disease and the severity of specific cognitive domains affected. Event related potentials (ERPs), especially P300, have been employed to evaluate the cognitive decline in MS and neurophysiological findings agree with data obtained by neuropsychological testing. The objectivity, the reliability and the easy administration are the main features of ERP technique but more specific attention and memory tasks are needed to enhance the clinical value of the methodology. Moreover, ERP recording has the advantage of being feasible even in severe disabled patients. Finally, longitudinal ERP studies are required to investigate the natural course of cognitive dysfunction in MS, to estimate the prognostic value of subclinical defects in different clinical form of the disease and to evaluate clinical benefits of therapeutic and rehabilitative interventions.

Functional magnetic resonance imaging response to increased verbal working memory demands among patients with multiple sclerosis

Multiple sclerosis (MS) patients frequently experience impaired verbal working memory (VWM). Functional magnetic resonance imaging (fMRI) may help identify neural mechanisms underlying these deficits. Neuroimaging studies of healthy adults have characterized responses associated with increased VWM demands during the n-Back task, suggesting that this experimental paradigm could help identify neural correlates of VWM deficits among MS patients. Fifteen MS patients and 15 matched control participants completed the n-Back during whole-brain fMRI. Mean signal during adjacent 0-Back blocks was subtracted, on a voxel-wise basis, from mean signal observed during n-Back blocks. Resulting difference scores for 1-, 2-, and 3-Back were compared across groups and difficulty levels. Signal intensity was positively related to difficulty level in anterior regions, including premotor, supplementary motor, and dorsolateral prefrontal cortices. MS patients exhibited significantly greater intensity in these areas compared to controls during the 1-Back, while portions of the left superior frontal gyrus, cingulate, and parahippocampal gyri were relatively less intense at more difficult levels. MS group responses were slower during the 1-Back and tended to be slower during the 3-Back; however, accuracy did not differ at any level. Lesion load was positively related to only 1-Back activity and unrelated to any performance measure. Results suggest that compensatory activity occurs among MS patients matched on performance accuracy. Furthermore, compensatory activity occurs predominantly in regions associated with VWM, and this may decline relative to controls as task demands increase. These findings may help to explain why MS patient performance decreases as a function of effort on neuropsychological tests.