Fatigue and fatigability in neurologic illnesses: proposal for a unified taxonomy

Predictors of Fatigue Impact in Persons With Long-Standing Multiple Sclerosis

BACKGROUND

Fatigue is a common experience among persons diagnosed with multiple sclerosis (MS). Fatigue negatively influences quality of life, interferes with activities of daily living, and impairs the ability to maintain gainful employment. Mechanisms underlying the pathophysiologic determinants of fatigue in MS are poorly understood, and effective treatments to manage fatigue present a challenge. Although the use of pharmacologic therapies is recommended to treat symptomatic fatigue, undertreatment of fatigue is common. Better long-term management and symptomatic relief may be provided by the use of nonpharmacologic treatments such as increased physical activity, energy conservation, and cognitive behavioral therapy.

METHODS

The purpose of this study was to explore the physical, cognitive, and psychosocial dimensions of fatigue impact among persons with long-standing MS-defined here as having been diagnosed with MS for 17 years or more. A sample of 331 participants with MS completed surveys measuring fatigue impact, MS-related functional limitation, depressive symptoms, barriers to health promotion, personal resources, and health promoting behaviors.

RESULTS

MS-related functional limitation and depressive symptoms were the strongest predictors of fatigue impact. MS-related functional limitation explained the greatest amount of variance in models predicting physical and psychosocial fatigue impact, whereas depressive symptoms explained the most variance in models predicting total and cognitive fatigue impact. Barriers to health promotion explained the least amount of variance among the models. Personal resources and health promoting behaviors were not significant predictors of fatigue impact in this study.

CONCLUSION

Interventions aimed at reducing MS-related functional limitations, depressive symptoms, and barriers to health promotion may have beneficial influences on fatigue impact, whereas actions designed to promote personal resource adequacy as well as engagement in health promoting behaviors may not translate into improvements in fatigue impact in persons with MS.

Effect of exercise interventions on perceived fatigue in people with multiple sclerosis: synthesis of meta-analytic reviews

Although exercise training has been advocated as a nonpharmacological treatment for multiple sclerosis (MS) related fatigue, no consensus exists regarding its effectiveness. To address this, we collated meta-analytic reviews that explored the effectiveness of exercise training for the treatment of MS-related fatigue. We searched five online databases for relevant reviews, published since 2005, and identified 172 records. Five reviews were retained for systematic extraction of information and evidence quality analysis. Although our review synthesis indicated that exercise training interventions have a moderate effect on fatigue reduction in people with MS, no clear insight was obtained regarding the relative effectiveness of specific types or modes of exercise intervention. Moreover, Grading of Recommendation Assessment, Development and Evaluation revealed that the overall quality of evidence emanating from these five reviews was ‘very low’.

Neuromuscular fatigue during exercise: Methodological considerations, etiology and potential role in chronic fatigue

The term fatigue is used to describe a distressing and persistent symptom of physical and/or mental tiredness in certain clinical populations, with distinct but ultimately complex, multifactorial and heterogenous pathophysiology. Chronic fatigue impacts on quality of life, reduces the capacity to perform activities of daily living, and is typically measured using subjective self-report tools. Fatigue also refers to an acute reduction in the ability to produce maximal force or power due to exercise. The classical measurement of exercise-induced fatigue involves neuromuscular assessments before and after a fatiguing task. The limitations and alternatives to this approach are reviewed in this paper in relation to the lower limb and whole-body exercise, given the functional relevance to locomotion, rehabilitation and activities of daily living. It is suggested that under some circumstances, alterations in the central and/or peripheral mechanisms of fatigue during exercise may be related to the sensations of chronic fatigue. As such, the neurophysiological correlates of exercise-induced fatigue are briefly examined in two clinical examples where chronic fatigue is common: cancer survivors and people with multiple sclerosis. This review highlights the relationship between objective measures of fatigability with whole-body exercise and perceptions of fatigue as a priority for future research, given the importance of exercise in relieving symptoms of chronic fatigue and/or overall disease management. As chronic fatigue is likely to be specific to the individual and unlikely to be due to a simple biological or psychosocial explanation, tailored exercise programmes are a potential target for therapeutic intervention.

Cognitive fatigue in patients with myasthenia gravis

INTRODUCTION

Cognitive fatigue has frequently been reported in myasthenia gravis (MG). However, objective assessment of cognitive fatigability has never been evaluated.

METHODS

Thirty-three MG patients with stable generalized disease and 17 healthy controls underwent a test battery including repeated testing of attention and concentration (d2-R) and Paced Auditory Serial Addition Test. Fatigability was based on calculation of linear trend (LT) reflecting dynamic performance within subsequent constant time intervals. Additionally, fatigue questionnaires were used.

RESULTS

MG patients showed a negative LT in second d2-R testing, indicating cognitive fatigability. This finding significantly differed from stable cognitive performance in controls (P < 0.05). Results of Paced Auditory Serial Addition Test testing did not differ between groups. Self-assessed fatigue was significantly higher in MG patients compared with controls (P < 0.001), but did not correlate with LT.

CONCLUSIONS

LT quantifies cognitive fatigability as an objective measurement of performance decline in MG patients. Self-assessed cognitive fatigue is not correlated with objective findings. Muscle Nerve 56: 449-457, 2017.

Nonlinear mixed-effects model reveals a distinction between learning and performance in intensive reach training post-stroke

BACKGROUND

We recently showed that individuals with chronic stroke who completed two sessions of intensive unassisted arm reach training exhibited improvements in movement times up to one month post-training. Here, we study whether changes in movement times during training can predict long-term changes.

METHODS

Sixteen participants with chronic stroke and ten non-disabled age-matched participants performed two sessions of reach training with 600 movements per session. Movement time data during training were fitted to a nonlinear mixed-effects model consisting of a decreasing exponential term to model improvements of performance due to learning and an increasing linear term to model worsening of performance due to activity-dependent fatigability and/or other factors unrelated to learning.

RESULTS

For non-disabled age-matched participants, movement times gradually decreased overall during training and overall changes in movement times during training predicted long-term changes. In contrast, for participants post-stroke, movement times often worsened near the end of training. As a result, overall changes in movement times during training did not predict long-term changes in movement times in the stroke group. However, improvements in movement times due to training, as estimated by the exponential term of the model, predicted long-term changes in movement times.

CONCLUSION

Participants post-stroke showed a distinction between learning and performance in unassisted intensive arm reach training. Despite worsening of performance in later trials, extended training was beneficial for long-term gains.

Tracking daily fatigue fluctuations in multiple sclerosis: ecological momentary assessment provides unique insights

Studies investigating the prevalence, cause, and consequence of multiple sclerosis (MS) fatigue typically use single measures that implicitly assume symptom-stability over time, neglecting information about if, when, and why severity fluctuates. We aimed to examine the extent of moment-to-moment and day-to-day variability in fatigue in relapsing-remitting MS and healthy individuals, and identify daily life determinants of fluctuations. Over 4 weekdays, 76 participants (38 relapsing-remitting MS; 38 controls) recruited from multiple sites provided real-time self-reports six times daily (n = 1661 observations analyzed) measuring fatigue severity, stressors, mood, and physical exertion, and daily self-reports of sleep quality. Fatigue fluctuations were evident in both groups. Fatigue was highest in relapsing-remitting MS, typically peaking in late-afternoon. In controls, fatigue started lower and increased steadily until bedtime. Real-time stressors and negative mood were associated with increased fatigue, and positive mood with decreased fatigue in both groups. Increased fatigue was related to physical exertion in relapsing-remitting MS, and poorer sleep quality in controls. In relapsing-remitting MS, fatigue fluctuates substantially over time. Many daily life determinants of fluctuations are similar in relapsing-remitting MS and healthy individuals (stressors, mood) but physical exertion seems more relevant in relapsing-remitting MS and sleep quality most relevant in healthy individuals.

Fatigue and its associated factors in liver transplant recipients in Beijing: a cross-sectional study

OBJECTIVES

Fatigue is a highly prevalent symptom experienced by patients who underwent the liver transplantation. However, the influencing factors of fatigue are poorly understood by healthcare professionals. The aim of this study was to examine the intensity, interference, duration and prevalence of fatigue in liver transplantation recipients and to explore the influencing factors of post-transplantation fatigue.

DESIGN

A cross-sectional design was used in this study.

METHODS

A convenience sample of liver transplant recipients was recruited at an outpatient transplant clinic of a general hospital in Beijing, China. Self-report survey data were provided by liver transplant recipients using the Fatigue Symptom Inventory (FSI), the Hospital Anxiety and Depression Scale (HADS), the Perceived Social Support Scale (PSSS) and the Athens Insomnia Scale (AIS). Demographic, clinical and psychosocial parameters were evaluated as fatigue influencing factors.

RESULTS

Participants (n=285) included 69 women and 216 men. Fatigue was found in 87.0% of liver transplant recipients. Mean scores of fatigue intensity items were 4.47±2.85, 1.93±1.97, 3.15±2.13 and 2.73±2.42 (most fatigue, least fatigue, average fatigue in the week prior to assessment and fatigue at the point of assessment). The mean score of fatigue interference was 2.27±2.09.The number of days fatigued in the week prior to assessment was 2.26±2.02 and the amount of time fatigued each day was 2.75±2.44. Spearman's correlation analysis showed that fatigue intensity was positively associated with anxiety, depression and insomnia (p<0.001 for all), while fatigue interference was positively associated with gender, anxiety, depression and insomnia (p<0.05 for all). In the multiple linear regression analysis, anxiety and insomnia were positively associated with fatigue intensity (p<0.001), and insomnia, depression and anxiety were positively associated with fatigue interference (p<0.001).

CONCLUSIONS

Fatigue is common in liver transplant recipients, and it is strongly associated with insomnia, anxiety and depression.

What's in the Literature?

In this edition of this column, we review new studies concerning the pathophysiology, treatment, and outcomes of patients with necrotizing myopathy, genetic testing in congenital myopathies, and limb girdle muscular dystrophies, and the incidence of polyneuropathy in the myotonic dystrophies. Various studies in myasthenia gravis, including those concerning antibody testing, clinical features, and quality of life are also reviewed as are recent findings in congenital myasthenic syndromes. Finally, 2 studies concerning polyneuropathy are discussed, including one on the association of polyneuropathy in patients with the metabolic syndrome and one on laboratory testing in patients with otherwise idiopathic small fiber polyneuropathy.

The Assessment of Motor Fatigability in Persons With Multiple Sclerosis: A Systematic Review

Background. Persons with multiple sclerosis (PwMS) are often characterized by increased motor fatigability, which is a performance change on an objectively measured criterion after any type of voluntary muscle contractions. This review summarizes the existing literature to determine which protocols and outcome measures are best to detect or study motor fatigability and the underlying mechanisms in MS. Methods. Two electronic databases, PubMed and Web of Science, were searched for relevant articles published until August 2016 with a combination of multiple sclerosis, fatigability, muscle fatigue, and motor fatigue. Results. A total of 48 articles were retained for data extraction. A variety of fatigability protocols were reported; protocols showed differences in type (isometric vs concentric), duration (15 to 180 s), and number of contractions (fixed or until exhaustion). Also, 12 articles reported motor fatigability during functional movements, predominantly assessed by changes in walking speed; 11 studies evaluated the mechanisms underlying motor fatigability, using additional electrical nerve or transcranial magnetic stimulation. Three articles reported psychometrics of the outcomes. Conclusions. The disparity of protocols and outcome measures to study different aspects of motor fatigability in PwMS impedes direct comparison between data. Most protocols use maximal single-joint isometric contractions, with the advantage of high standardization. Because there is no head-to-head comparison of the different protocols and only limited information on psychometric properties of outcomes, there is currently no gold standard to assess motor fatigability. The disability level, disease phenotype, and studied limb may influence the assessment of motor fatigability in PwMS.

The Need for Standardized Assessment of Muscle Quality in Skeletal Muscle Function Deficit and Other Aging-Related Muscle Dysfunctions: A Symposium Report

A growing body of scientific literature suggests that not only changes in skeletal muscle mass, but also other factors underpinning muscle quality, play a role in the decline in skeletal muscle function and impaired mobility associated with aging. A symposium on muscle quality and the need for standardized assessment was held on April 28, 2016 at the International Conference on Frailty and Sarcopenia Research in Philadelphia, Pennsylvania. The purpose of this symposium was to provide a venue for basic science and clinical researchers and expert clinicians to discuss muscle quality in the context of skeletal muscle function deficit and other aging-related muscle dysfunctions. The present article provides an expanded introduction concerning the emerging definitions of muscle quality and a potential framework for scientific inquiry within the field. Changes in muscle tissue composition, based on excessive levels of inter- and intra-muscular adipose tissue and intramyocellular lipids, have been found to adversely impact metabolism and peak force generation. However, methods to easily and rapidly assess muscle tissue composition in multiple clinical settings and with minimal patient burden are needed. Diagnostic ultrasound and other assessment methods continue to be developed for characterizing muscle pathology, and enhanced sonography using sensors to provide user feedback and improve reliability is currently the subject of ongoing investigation and development. In addition, measures of relative muscle force such as specific force or grip strength adjusted for body size have been proposed as methods to assess changes in muscle quality. Furthermore, performance-based assessments of muscle power via timed tests of function and body size estimates, are associated with lower extremity muscle strength may be responsive to age-related changes in muscle quality. Future aims include reaching consensus on the definition and standardized assessments of muscle quality, and providing recommendations to address critical clinical and technology research gaps within the field.

Potential pathophysiological pathways that can explain the positive effects of exercise on fatigue in multiple sclerosis: A scoping review

BACKGROUND

Fatigue is one of the most common and most disabling symptoms of multiple sclerosis (MS). It is a multidimensional and complex symptom with multifaceted origins, involving both central and peripheral fatigue mechanisms. Exercise has proven to be safe for people with MS, with cumulating evidence supporting significant reductions in fatigue. However, the potential pathophysiological pathways that can explain the positive effects of exercise on fatigue in MS remain elusive.

OBJECTIVES

The objectives were, in PwMS (1) to update the knowledge on the pathophysiology underlying primary and secondary fatigue, and (2) to discuss potential pathophysiological pathways that can explain the positive effects of exercise on MS fatigue.

METHODS

A comprehensive literature search of six databases (PubMed, Embase, Cochrane Library, PEDro, CINAHL and SPORTDiscus) was performed. To be included, the study had to 1) enroll participants with definite MS according to defined criteria, 2) assess explicit pathophysiological mechanisms related to MS fatigue, 3) be available in English, Danish or French, and 4) had undergone peer-review.

RESULTS

A total of 234 studies fulfilled the inclusion criteria. Primary MS fatigue mainly originated from a dysfunction of central nervous system neuronal circuits secondary to increased inflammation, reduced glucose metabolism, brain atrophy and diffuse demyelination and axonal lesions. Secondary MS fatigue was linked with sleep disturbances, depression, cognitive impairments, and deconditioning. Cardiovascular, immunologic, neuroendocrine, and neurotrophic changes associated with exercise may alleviate primary MS fatigue while exercise may improve secondary MS fatigue through symptomatic improvement of deconditioning, sleep disorders, and depression.

CONCLUSIONS

>30 primary and secondary pathophysiological fatigue pathways were identified underlining the multidimensionality and complexity of MS fatigue. Though the underlying key cellular and molecular cascades still have to be fully elucidated, exercise holds the potential to alleviate MS fatigue, through both primary and secondary fatigue pathways.

The impact of subjective cognitive fatigue and depression on cognitive function in patients with multiple sclerosis

BACKGROUND

The association between subjective cognitive fatigue and objective cognitive dysfunction in patients with multiple sclerosis (PwMS) has been studied, with conflicting results.

OBJECTIVE

To explore the impact of fatigue on cognitive function, while controlling for the influence of depression, disability, comorbidities, and psychotropic medications.

METHODS

PwMS completed a computerized cognitive testing battery with age- and education-adjusted cognitive domain scores. Disability (Expanded Disability Status Scale (EDSS)), cognitive fatigue, and depression were concurrently evaluated.

RESULTS

In all, 699 PwMS were included. Both cognitive fatigue and depression were significantly and negatively correlated with the same cognitive domains: information processing speed, executive function, attention, motor function, and memory (-0.15 ⩽ r ⩽ -0.14 for cognitive fatigue; -0.24 ⩽ r ⩽ -0.19 for depression). Multivariate analysis revealed significant but small independent correlations only between depression and neuropsychological test results, while cognitive fatigue had no independent correlation with objective cognitive function except for a trend toward impaired motor function in highly fatigued PwMS. Depression and cognitive fatigue accounted for no more than 6% of the variance in objective cognitive domain scores.

CONCLUSION

Cognitive fatigue is not independently related to objective cognitive impairment. Depression may influence cognitive function of PwMS primarily when it is severe. Cognitive impairment in PwMS should not be ascribed to fatigue or mild depression.

THE ANALYSIS OF RELATIONSHIP BETWEEN LESION OF FUNCTIONAL SYSTEMS OF NERVOUS SYSTEM AND SEVERITY OF FATIGUE IN PATIENTS WITH MULTIPLE SCLEROSIS

Despite numerous investigations, fatigue remains one of the least studied manifestations of MS. However, significant prevalence of this symptom proves importance of its study. The aim of the study was to define a prognostic assessment of fatigue development accompanying lesions of certain functional systems and degree of disability. Material and methods. 96 patients, aged 15 to 58 years with a diagnosis of MS have been examined. MS patients were examined with the same protocol, using formalized scales. To detect fatigue and determine the degree of its severity was used Fatigue Severity Scale (FSS). The degree of disability in patients was assessed by Kurtzke EDSS (Expanded Disability Status Scale). Statistical methods for the data analysis were also used, including methods of descriptive statistics, probability assessment and prognostic significance of obtained data using odds ratio (OR). Results. Fatigue was detected in 49.1% of patients with a degree of disability lower than 4 EDSS scores and in 90.4% of patients with disability higher than 4 EDSS scores (p=0.0027). The assessment of functional systems at the time of observation has statistically significant prognostic values according to the following parameters: pyramidal system lesion (OR=7.43 (2.43–22.76)), coordination disorders (OR=4.60 (1.05–20.25)), cranial nerve lesion (OR=4.33 (1.40–13.39)), (p<0.05). Lesion of the pyramidal and coordination systems at the onset of the disease may increase risk for detection of fatigue higher than 4 scores in the follow-up observation (lesion of pyramidal system – OR=1.62 (0.5–5.25), coordination disorders OR=1.41 (0.58–5.16)). Conclusion. The results of our investigation showed that symptom of fatigue is observed in almost 90 % of MS patients. The study showed that fatigue in MS patients depends on the degree of disability and lesions of certain functional systems.

Fatigue in Parkinson's disease

Fatigue is one of the most common nonmotor symptoms in Parkinson's disease and may affect a wide range of everyday activities, cause disability and reduce quality of life. It occurs at every stage of PD, and once present will often persist and may worsen over time. Lack of a consensus of definition and classification, and a range of different self-reporting scales has so far made the study of fatigue challenging. We review a unifying taxonomy for defining fatigue in clinical and research contexts as well as case definition criteria for PD-related fatigue. The potential causes of fatigue in PD are discussed as are recommendations for treatment.

Acute-Phase Fatigue Predicts Limitations with Activities of Daily Living 18 Months after First-Ever Stroke

BACKGROUND

Fatigue during the acute phase following stroke has been shown to predict long-term physical health, specifically increased bodily pain and poorer self-rated general health. The aim of this analysis was to determine whether acute-phase fatigue also predicts patients' limitations in activities of daily living (ADL) 18 months after the first stroke.

METHODS

Patients with first-ever stroke (N = 88) were recruited upon admission at 2 hospitals in Norway. Patients were assessed within 2 weeks following admission and at 18 months using the Barthel Index of Activities of Daily Living (BI), Fatigue Severity Scale, and Beck Depression Inventory II. The relationship between acute-phase fatigue and later activity limitations (BI < 20) was evaluated using multivariate logistic regression analysis controlling for relevant covariates and acute-phase ADL function.

RESULTS

Acute-phase fatigue was associated with activity limitations at 18-month follow-up (P = .002), even when controlling for other predictors of ADL function, including age, gender, baseline work status, and acute-phase depressive symptoms and ADL function. Examining the reverse relationship, acute-phase activity limitations were unrelated to fatigue 18 months after stroke.

CONCLUSION

Our study indicates that acute-phase fatigue may be an independent risk factor for activity limitations 18 months after stroke. This finding suggests that effective treatments for poststroke fatigue both in the acute phase and later in the recovery period may contribute to better stroke rehabilitation.

Reduced activation in isometric muscle action after lengthening contractions is not accompanied by reduced performance fatigability

After active lengthening contractions, a given amount of force can be maintained with less muscle activation compared to pure isometric contractions at the same muscle length and intensity. This increase in neuromuscular efficiency is associated with mechanisms of stretch-induced residual force enhancement. We hypothesized that stretch-related increase in neuromuscular efficiency reduces fatigability of a muscle during submaximal contractions. 13 subjects performed 60 s isometric knee extensions at 60% of maximum voluntary contraction (MVC) with and without prior stretch (60°/s, 20°). Each 60 s trial was preceded and followed by neuromuscular tests consisting of MVCs, voluntary activation (VA) and resting twitches (RT), and there was 4 h rest between sets. We found a significant (p = 0.036) 10% reduction of quadriceps net-EMG after lengthening compared to pure isometric trials. However, increase in neuromuscular efficiency did not influence the development of fatigue. Albeit we found severe reduction of MVC (30%), RT (30%) and VA (5%) after fatiguing trials, there were no differences between conditions with and without lengthening. As the number of subjects showing no activation reduction increased with increasing contraction time, intensity may have been too strenuous in both types of contractions, such that a distinction between different states of fatigue was not possible anymore.

Effects of Sprint Interval Cycling on Fatigue, Energy, and Cerebral Oxygenation

INTRODUCTION

Feelings of fatigue are reduced after a session of continuous exercise of low-to-moderate intensity lasting 20 min or more, but only when feelings of energy are increased. Feelings of fatigue and energy have not been described after fatiguing, high-intensity interval exercise. Cerebral oxygenation has been implicated as a central correlate of fatigability, but it has not been studied concurrent with perceived fatigue during or after exercise.

METHODS

Fifteen recreationally active participants (8 women, 7 men) completed bouts of sprint interval cycling (four, 30-s all-out sprints each followed by 4 min of active recovery) and a time- and work-matched bout of constant resistance cycling. Oxygenation (oxygenated hemoglobin [HbO2]) and deoxygenation (deoxygenated hemoglobin [HHb]) in the dorsolateral prefrontal cortex were measured using near-infrared spectroscopy. Fatigue ratings during each sprint and feelings of fatigue and energy during recovery were assessed.

RESULTS

Increases in HbO2 and HHb in frontal cortex were greater during sprint cycling than during constant resistance cycling (P = 0.001). Fatigability (decreased power output) increased over successive sprints (P = 0.001). About 95% of the increase in fatigue ratings across sprints (P < 0.001) was accounted for by fatigability and cortical HbO2. Feelings of fatigue were decreased (P < 0.001) and feelings of energy were increased (P < 0.05) across sprint recovery periods but were unchanged during constant resistance cycling. About 85% of the changes in feelings of fatigue or energy during recovery were explained by fatigue ratings across sprints and maximum HbO2 in the cortex during recovery.

CONCLUSION

Repeated, high-intensity sprints were fatiguing, but paradoxical reductions in feelings of fatigue and increases in feelings of energy occurred during recovery that were accounted for by ratings of fatigue during exercise and oxygenation in the dorsolateral prefrontal cortex during recovery.

The relationship between fatigability and sleep quality in people with multiple sclerosis

BACKGROUND

Perceived fatigue and fatigability are constructs of multiple sclerosis (MS)-related fatigue. Sleep disturbances lead to poor sleep quality, which has been found to be associated with perceived fatigue in people with MS (PwMS). However, the relationship between fatigability and sleep quality is unknown.

OBJECTIVE

To explore the relationship between physical and cognitive fatigability with self-reported and objective measures of sleep quality in PwMS.

METHODS

Fifty-one ambulatory PwMS participated in the study. Physical fatigability was measured by percent-change in meters walked on the six-minute walk test (6MWT) and in force exerted on a repeated maximal hand grip test. Cognitive fatigability was measured using response speed variability on the continuous performance test. Self-report sleep quality was measured using the Pittsburgh Sleep Quality Index, and objective sleep quality was measured using 1 week of actigraphy.

RESULTS

Components of the Pittsburgh Sleep Quality Index and several actigraph parameters were significantly associated with physical fatigability and cognitive fatigability. However, controlling for depression eliminated the association between the sleep outcomes and cognitive fatigability and attenuated the association between the sleep outcomes and physical fatigability.

CONCLUSION

Poor sleep quality is related to fatigability in MS but depression appears to mediate these relationships.

Fatigue, Sleep Disturbances, and Their Influence on Quality of Life in Cervical Dystonia Patients

Background

Nonmotor symptoms (NMS) are highly prevalent in cervical dystonia (CD). In general, fatigue and sleep are important NMS that determine a decreased health-related quality of life (HR-QoL), but their influence in CD is unknown. The authors systematically investigated fatigue, excessive daytime sleepiness (EDS), and sleep quality in patients with CD and controls and assessed the influence of psychiatric comorbidity, pain, and dystonia motor severity. They also examined the predictors of HR-QoL.

Methods

The study included 44 patients with CD and 43 matched controls. Fatigue, EDS, and sleep quality were assessed with quantitative questionnaires and corrected for depression and anxiety using analysis of covariance. The Toronto Western Spasmodic Torticollis Rating Scale and the Clinical Global Impression Scale-jerks/tremor subscale were used to score motor severity and to assess whether motor characteristics could explain an additional part of the variation in fatigue and sleep-related measures. HR-QoL was determined with the RAND-36 item Health Survey, and predictors of HR-QoL were assessed using multiple regression.

Results

Fatigue scores were increased independently from psychiatric comorbidity (4.0 vs. 2.7; P < 0.01), whereas EDS (7.3 vs. 7.4; P = 0.95) and sleep quality (6.5 vs. 6.1; P = 0.73) were highly associated with depression and anxiety. In patients with CD, motor severity did not explain the variations in fatigue (change in the correlation coefficient [ΔR²] = 0.06; P = 0.15), EDS (ΔR² = 0.00; P = 0.96), or sleep quality (ΔR² = 0.04; P = 0.38) scores. Fatigue, EDS, psychiatric comorbidity, and pain predicted a decreased QoL.

Conclusion

Independent from psychiatric comorbidity and motor severity, fatigue appeared to be a primary NMS. Sleep-related measures were highly associated with psychiatric comorbidity, but not with motor severity. Only NMS predicted HR-QoL, which emphasizes the importance of attention to NMS in patients with CD.

Assessment of patients with multiple sclerosis according to tests of the Multiple Sclerosis Functional Composite

Abstract Introduction: The Multiple Sclerosis Functional Composite (MSFC) is a scale that evaluates the functional and cognitive aspects of patients with multiple sclerosis (MS). Objective: To compare the performance of individuals with the relapsing-remitting form of MS (RRMS) with a group of healthy subjects using the MSFC. Methods: Twenty subjects were investigated in this study, consisting of 10 patients with clinical diagnosis of RRMS and 10 controls with similar gender and age to the group with the disease. The three tests that comprise the MSFC were used for the evaluation of gait, upper limb motor function and cognition (memory and processing speed). Student's t-test was used to assess data with normal distribution and data with skewed distribution were evaluated using the Mann-Whitney test. Results: The results showed that the patients with RRMS took longer to perform the locomotion test (6.91 ± 2.35) compared to the control group (5.16 ± 1.28). The MS group (22.06 ± 5.44) also showed greater difficulty in performing a task with the dominant upper limb compared to the healthy subjects (17.79 ± 2.96). No statistically significant difference was found between the groups in the performance of cognitive tasks (p = .65). Conclusion: The use of the MSFC tests proved valuable for measuring possible motor and cognitive impairments in patients with RRMS. Thus, it is suggested that this scale is adopted in clinical practice, improving therapies for the treatment of MS patients and thereby providing them a better quality of life.

Operationalising cognitive fatigability in multiple sclerosis: A Gordian knot that can be cut?

BACKGROUND

Researchers have attempted to operationalise objective measures of cognitive fatigability in multiple sclerosis (MS) to overcome the perceived subjectivity of patient-reported outcomes of fatigue (PROs). Measures of cognitive fatigability examine decrements in performance during sustained neurocognitive tasks.

OBJECTIVE

This personal viewpoint briefly summarises available evidence for measures of cognitive fatigability in MS and considers their overall utility.

RESULTS

Studies suggest there may be a construct that is distinct from self-reported fatigue, reflecting a new potential intervention target. However, assessments vary and findings across and within measures are inconsistent. Few measures have been guided by a coherent theory, and those identified are likely to be influenced by other confounds, such as cognitive impairment caused more directly by disease processes, depression and assessment biases.

CONCLUSION

Future research may benefit from (a) developing a guiding theory of cognitive fatigability, (b) examining ecological and construct validity of existing assessments and (c) exploring whether the more promising cognitive fatigability measures are correlated with impaired functioning after accounting for possible confounds. Given the issues raised, we caution that our purposes as researchers may be better served by continuing our search for a more objective cognitive fatigability construct that runs in parallel with improving, rather than devaluing, current PROs.

The Berlin Treatment Algorithm: recommendations for tailored innovative therapeutic strategies for multiple sclerosis-related fatigue

More than 80% of multiple sclerosis (MS) patients suffer from fatigue. Despite this, there are few therapeutic options and evidence-based pharmacological treatments are lacking. The associated societal burden is substantial (MS fatigue is a major reason for part-time employment or early retirement), and at least one out of four MS patients view fatigue as the most burdensome symptom of their disease. The mechanisms underlying MS-related fatigue are poorly understood, and objective criteria for distinguishing and evaluating levels of fatigue and tiredness have not yet been developed. A further complication is that both symptoms may also be unspecific indicators of many other diseases (including depression, sleep disorders, anemia, renal failure, liver diseases, chronic obstructive pulmonary disease, drug side effects, recent MS relapses, infections, nocturia, cancer, thyroid hypofunction, lack of physical exercise). This paper reviews current treatment options of MS-related fatigue in order to establish an individualized therapeutic strategy that factors in existing comorbid disorders. To ensure that such a strategy can also be easily and widely implemented, a comprehensive approach is needed, which ideally takes into account all other possible causes and which is moreover cost efficient. Using a diagnostic interview, depressive disorders, sleep disorders and side effects of the medication should be identified and addressed. All MS patients suffering from fatigue should fill out the Modified Fatigue Impact Scale, Epworth Sleepiness Scale, the Beck Depression Inventory (or a similar depression scale), and the Pittsburgh Sleep Quality Index (or the Insomnia Severity Index). In some patients, polygraphic or polysomnographic investigations should be performed. The treatment of underlying sleep disorders, drug therapy with alfacalcidol or fampridine, exercise therapy, and cognitive behavioral therapy-based interventions may be effective against MS-related fatigue. The objectives of this article are to identify the reasons for fatigue in patients suffering from multiple sclerosis and to introduce individually tailored treatment approaches. Moreover, this paper focuses on current knowledge about MS-related fatigue in relation to brain atrophy and lesions, cognition, disease course, and other findings in an attempt to identify future research directions.

Allostatic Self-efficacy: A Metacognitive Theory of Dyshomeostasis-Induced Fatigue and Depression

This paper outlines a hierarchical Bayesian framework for interoception, homeostatic/allostatic control, and meta-cognition that connects fatigue and depression to the experience of chronic dyshomeostasis. Specifically, viewing interoception as the inversion of a generative model of viscerosensory inputs allows for a formal definition of dyshomeostasis (as chronically enhanced surprise about bodily signals, or, equivalently, low evidence for the brain's model of bodily states) and allostasis (as a change in prior beliefs or predictions which define setpoints for homeostatic reflex arcs). Critically, we propose that the performance of interoceptive-allostatic circuitry is monitored by a metacognitive layer that updates beliefs about the brain's capacity to successfully regulate bodily states (allostatic self-efficacy). In this framework, fatigue and depression can be understood as sequential responses to the interoceptive experience of dyshomeostasis and the ensuing metacognitive diagnosis of low allostatic self-efficacy. While fatigue might represent an early response with adaptive value (cf. sickness behavior), the experience of chronic dyshomeostasis may trigger a generalized belief of low self-efficacy and lack of control (cf. learned helplessness), resulting in depression. This perspective implies alternative pathophysiological mechanisms that are reflected by differential abnormalities in the effective connectivity of circuits for interoception and allostasis. We discuss suitably extended models of effective connectivity that could distinguish these connectivity patterns in individual patients and may help inform differential diagnosis of fatigue and depression in the future.

Fatigue in myasthenia gravis: risk factors and impact on quality of life

OBJECTIVES

Emerging evidence suggests that fatigue in myasthenia gravis (MG) is a relevant problem that negatively impacts activities of daily living (ADL). The relationship between fatigue and quality of life (QoL) has never been systematically explored in MG patients. The study aimed to assess the prevalence of fatigue and its relation to ADL and QoL as well as to identify factors associated with fatigue in MG.

MATERIAL AND METHODS

This was a cross-sectional observational study in patients with confirmed diagnosis of MG independent of disease severity. Prevalence of fatigue was assessed using the Chalder Fatigue Scale (CFQ). Impact of fatigue on ADL and QoL was assessed by the MG activities of daily living profile (MG-ADL) and the MG-specific quality-of-life instrument (MG-QoL), respectively. Association of fatigue with sociodemographics, clinical characteristics of MG, and comorbidities including mood and anxiety disorders as well as sleep disorders was investigated using multivariable logistic regression analyses.

RESULTS

Overall, 200 MG patients were included. The observed rate of fatigue was 56.1%, of those 70.4% fulfilled the criteria of chronic fatigue (CF) with a duration of ≥6 months. Relevant fatigue was strongly associated to ADL and QoL. Factors associated with relevant fatigue were disease severity and depressive state. Furthermore, positive muscle-specific tyrosine kinase (MuSK) antibody status showed a strong association with relevant fatigue.

CONCLUSIONS

MG patients have a high prevalence of fatigue which negatively impacts ADL and QoL. MG-specific clinical characteristics are related to fatigue and might help to identify MG patients at risk for fatigue.

Assessment of fatigability of older women during sit-to-stand performance

BACKGROUND

Fatigability of older adults is relevant with regard to physical performance, falls and physical activity. Objective and inexpensive assessment tools for testing fatigability in the persons' home environment are not available.

AIMS

The aim of this study was to develop a protocol to objectively measure fatigability during repeated sit-to-stand performance in older persons.

METHODS

Decrease of maximum velocity of performance during repeated sit-to-stand transfers and the number of repetition when achieving a 10, 15, and 20 % fatigue threshold were measured in 49 community-dwelling older women using a linear encoder.

RESULTS

Mean maximum velocity of the sit-to-stand performance was 1.12 m/s (SD 0.17 m/s) with an estimated change of velocity per repetition of -0.0037 m/s (95 % CI -0.0039 to -0.0035) during the test. The mean number of repetitions representing 10, 15, and 20 % fatigue threshold was 8.1, 13.8, and 21, respectively.

DISCUSSION

This simple test protocol provides objective information about the decrease of performance of a daily task in older adults.

CONCLUSION

Fatigability of the sit-to-stand performance can be measured objectively by measuring the decrease of maximum velocity of consecutive repetitions and the repetition number achieving a 20 % fatigue threshold.

The Impact of MS-Related Cognitive Fatigue on Future Brain Parenchymal Loss and Relapse: A 17-Month Follow-up Study

Background

Fatigue is a disabling syndrome in multiple sclerosis (MS), which may be associated with inflammation and faster disease progression.

Objective

To analyze the significance of cognitive fatigue for subsequent disease progression.

Method

We followed 46 MS patients and 14 healthy controls in a study over 17 months. At the beginning (t1) and at the end (t2) of the study participants scored their fatigue, performed the Multiple Sclerosis Functional Composite and received MRI scanning, encompassing MPR T1, FLAIR, and DTI sequences. At t1, MS patients were divided into those with and those without cognitive fatigue (cut-off score for moderate cognitive fatigue of the Fatigue Scale for Motor and Cognition). We calculated ANCOVAs for repeated measurement to analyze the relevance of cognitive fatigue status for the number of relapses and for MRI parameters.

Results

At t1, but not at t2, patients with cognitive fatigue showed increased axial and radial diffusivity of corpus callosum fibers. At t2, these patients showed significantly more loss of brain parenchyma and greater enlargement of lateral ventricles. Moreover, they developed more relapses, but there was no difference in lesion load or in performance deterioration. Additional analyses showed that only cognitive fatigue but not a more general score for fatigue (Fatigue Severity Scale) had an impact on the worsening of the disease status.

Conclusion

Patients with cognitive fatigue may develop more brain atrophy and relapses during the next 17 months than patients without cognitive fatigue. Hence, experiencing cognitive fatigue might indicate more aggressive inflammatory processes and subsequent neurodegeneration.

Compensatory Neural Activity in Response to Cognitive Fatigue

Prolonged continuous performance of a cognitively demanding task induces cognitive fatigue and is associated with a time-related deterioration of objective performance, the degree of which is referred to cognitive fatigability. Although the neural underpinnings of cognitive fatigue are poorly understood, prior studies report changes in neural activity consistent with deterioration of task-related networks over time. While compensatory brain activity is reported to maintain motor task performance in the face of motor fatigue and cognitive performance in the face of other stressors (e.g., aging) and structural changes, there are no studies to date demonstrating compensatory activity for cognitive fatigue. High-density electroencephalography was recorded from human subjects during a 160 min continuous performance of a cognitive control task. While most time-varying neural activity showed a linear decline over time, we identified an evoked potential over the anterior frontal region which demonstrated an inverted U-shaped time-on-task profile. This evoked brain activity peaked between 60 and 100 min into the task and was positively associated with better behavioral performance only during this interval. Following the peak and during subsequent decline of this anterior frontal activity, the rate of performance decline also accelerated. These findings demonstrate that this anterior frontal brain activity, which is not part of the primary task-related activity at baseline, is recruited to compensate for fatigue-induced impairments in the primary task-related network, and that this compensation terminates as cognitive fatigue further progresses. These findings may be relevant to understanding individual differences in cognitive fatigability and developing interventions for clinical conditions afflicted by fatigue.

SIGNIFICANCE STATEMENT

Fatigue refers to changes in objective performance and subjective effort induced by continuous task performance. We examined the neural underpinnings of cognitive fatigue in humans using a prolonged continuous performance task and high-density electroencephalography with the goal of determining whether compensatory processes exist to maintain performance in the face of fatigue. We identified brain activity demonstrating an inverted U-shaped time-on-task profile. This brain activity showed features consistent with a compensatory role including: peaking between 60 and 100 min into the task, a positive association with behavioral performance only during this interval, and accelerated performance decline following its peak. These findings may be relevant to understanding individual differences in cognitive fatigue and developing interventions for clinical conditions afflicted by fatigue.

Motor fatigability after low-intensity hand grip exercises in persons with multiple sclerosis

INTRODUCTION

During maximal, sustained contractions, persons with multiple sclerosis (PwMS) show higher motor fatigability in comparison with healthy persons. It is not known if motor fatigability is also different between PwMS and healthy persons during low-intensity exercises. Thus, the aim of this study was to determine the difference in hand grip fatigability between healthy persons and PwMS for both hands during low-intensity hand grip exercises.

METHODS

19 PwMS and 19 healthy controls performed 18min of hand grip exercises at a maximum of 25% of the maximal voluntary strength, with an electronic hand dynamometer. Perceived fatigability, maximal hand grip strength and muscle activity (electromyography) of the wrist flexors and extensors were recorded in between these exercises for the dominant and non-dominant hand.

RESULTS AND DISCUSSION

There was a significant decrease in maximal hand grip strength after exercising in both groups and for both hands, mainly situated in the first 6min. In contrast to what was hypothesized, PwMS did not show more decline in strength than healthy controls, neither in the dominant nor the non-dominant hand. There was no group difference in the increase of the perceived fatigability in the dominant hand. However, for the non-dominant hand, the perceived fatigability after exercising increased more in PwMS than in healthy controls. Additionally, there was no relation between fatigue indices, as assessed with short maximal contractions and the strength decline after low-intensity repetitive exercises.

Fatigue in Multiple Sclerosis: Misconceptions and Future Research Directions

Fatigue is one of the most disabling side effects in people with multiple sclerosis. While this fact is well known, there has been a remarkable lack of progress in determining the pathophysiological mechanisms behind fatigue and the establishment of effective treatments. The main barrier has been the lack of a unified definition of fatigue that can be objectively tested with validated experimental models. In this “perspective article” we propose the use of the following model and definition of fatigue: the decrease in physical and/or mental performance that results from changes in central, psychological, and/or peripheral factors. These changes depend on the task being performed, the environmental conditions it is performed in, and the physical and mental capacity of the individual. Our definition and model of fatigue outlines specific causes of fatigue and how it affects task performance. We also outline the strengths and weaknesses of commonly used measures of fatigue and suggest, based on our model and definition, new research strategies, which should include multiple measures. These studies should be mechanistic with validated experimental models to determine changes in central, psychological, and/or peripheral factors that explain fatigue. The proposed new research strategies may lead to the identification of the origins of MS related fatigue and the development of new, more effective treatments.

The Pathophysiology of Fatigue in Parkinson's Disease and its Pragmatic Management

BACKGROUND

Fatigue is 1 of the most common and most disabling symptoms among patients with Parkinson's disease (PD) and has a significant impact on their quality of life. Yet the pathophysiology of fatigue is poorly understood, while its treatment is "limited to an empirical approach based on plausible hypotheses."

METHODS

PubMed was searched for articles with the key words "Parkinson's disease" or "parkinsonism" and "fatigue" that were published by or before August 2015. The analysis of articles, which were selected on subjective grounds, was used to review the current knowledge of pathophysiology and treatment outcomes in studies focused on fatigue in PD.

CONCLUSIONS

Clinical and experimental findings support the view that fatigue is a primary manifestation of PD. The main hypothesized pathophysiological mechanisms include abnormal basal ganglia (BG)-cortical mechanisms, particularly frontal loops, and an imbalance between neurotransmitters (e.g., dopamine [DA] and serotonin), along with an altered hypothalamus-pituitary-adrenal axis, neuroinflammation, cardiac sympathetic denervation, etc. Pragmatic treatment of fatigue in patients with PD includes various pharmacological (dopaminergic and psychostimulant drugs, antidepressants) and nonpharmacological strategies, although current knowledge suffers from insufficient evidence to support the use of any drug or nondrug therapy.

Central fatigue in multiple sclerosis: a review of the literature

CONCEPT

Fatigue is a major concern for patients with multiple sclerosis (MS). A clear definition of MS-related fatigue is a prerequisite for appropriate instruments for fatigue assessment. In turn, accurate assessment of fatigue in MS will enhance exploration of plausible mechanisms underlying this common and distressing symptom. Content/Objectives: To provide an integrative review of the current literature on theoretical models used to study fatigue in MS, instruments used to assess fatigue and other factors that impact fatigue during the various phases of MS.

DATA SOURCES

PUBMED, OVID, Ovid Health Star, Ovid MEDINE, CINAHL, Health and Psychosocial Instruments (HaPI), and PsycINFO. Seventeen articles fit the inclusion criteria and were included in the review.

RESULTS

Definitions of MS-related fatigue are reviewed. Several studies found a link with neurotransmitter dysfunction, circadian rhythm, and the timing of fatigue. Central fatigue in MS is associated with neurotransmitters disruptions as well as circadian rhythm disorders, but the evidence is not strong. Perceptions of fatigue or fatigability may arise as either a primary or secondary manifestation of disease. Based on findings from the literature review, a theoretical model of fatigue in MS is proposed.

CONCLUSION

Future research on MS-related fatigue may consider a longitudinal design with a carefully selected self-report instrument to advance understanding of the underlying pathological mechanisms.

The Effects of Performance Fatigability on Postural Control and Rehabilitation in the Older Patient

Fatigue is common in older adults and has a significant effect on quality of life. Despite the high prevalence of fatigue in older individuals, several aspects are poorly understood. It is important to differentiate subjective fatigue complaints from fatigability of motor performance because the two are independent constructs with potentially distinct consequences on mobility. Performance fatigability is the magnitude of change in a performance criterion over a given time of task performance. Performance fatigability is a compulsory element of any strength training program, yet strength training is an important component of rehabilitation programs for older adults. The consequences of fatigability for older adults suggest that acute exercise of various types may result in acute impairments in postural control. The effects of performance fatigability on postural control in older adults are evaluated here to aid the rehabilitation clinician in making recommendations for evaluation of fall risks and exercise prescription.

Clinical Utility of Mindfulness Training in the Treatment of Fatigue After Stroke, Traumatic Brain Injury and Multiple Sclerosis: A Systematic Literature Review and Meta-analysis

BACKGROUND

Fatigue is a common symptom following neurological illnesses and injuries, and is rated as one of the most debilitating sequela in conditions such as stroke, traumatic brain injury (TBI), and multiple sclerosis (MS). Yet effective treatments are lacking, suggesting a pressing need for a better understanding of its etiology and mechanisms that may alleviate the symptoms. Recently mindfulness-based interventions have demonstrated promising results for fatigue symptom relief.

OBJECTIVE

Investigate the efficacy of mindfulness-based interventions for fatigue across neurological conditions and acquired brain injuries.

MATERIALS AND METHODS

Systematic literature searches were conducted in PubMed, Medline, Web of Science, and PsycINFO. We included randomized controlled trials applying mindfulness-based interventions in patients with neurological conditions or acquired brain injuries. Four studies (N = 257) were retained for meta-analysis. The studies included patients diagnosed with MS, TBI, and stroke.

RESULTS

The estimated effect size for the total sample was -0.37 (95% CI: -0.58, -0.17).

CONCLUSION

The results indicate that mindfulness-based interventions may relieve fatigue in neurological conditions such as stroke, TBI, and MS. However, the effect size is moderate, and further research is needed in order to determine the effect and improve our understanding of how mindfulness-based interventions affect fatigue symptom perception in patients with neurological conditions.

[Pathological fatigue and fatigability after stroke]

AIM

To compare the phenomena of pathological fatigue and fatigability in patients after stroke.

MATERIAL AND METHODS

Forty-two patients were examined 6-24 months after stroke onset. Fatigue and fatigability were assessed by Russian versions of the Fatigue Assessment Scale and the Dutch Exertional Fatigue Scale, respectively.

RESULTS AND CONCLUSION

The severity of both fatigue and fatigability was related to the levels of anxiety and depression. The degree of fatigability, but not fatigue, depended on the severity of cognitive and physical deficits. Thus, fatigue and fatigability after stroke represent different phenomena.

The effect of hypopituitarism on fatigue after subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Aneurysmal subarachnoid hemorrhage (SAH) survivors often complain of fatigue, which is disabling. Fatigue is also a common symptom of pituitary dysfunction (PD), in particular in patients with growth hormone deficiency (GHD). A possible association between fatigue after SAH and long-term pituitary deficiency in SAH survivors has not yet been established.

METHODS

A single center observational study was conducted amongst 84 aneurysmal SAH survivors to study the relationship between PD and fatigue over time after SAH, using mixed model analysis. Fatigue was measured with the Fatigue Severity Scale and its relationships with other clinical variables were studied.

RESULTS

Three-quarters of respondents (76%) have pathological fatigue directly after SAH and almost two-thirds (60%) of patients still have pathological levels of fatigue after 14 months. The severity of SAH measured with a World Federation of Neurosurgical Societies (WFNS) score higher than 1 (P = 0.008) was associated with long-term fatigue. There is no statistically significant effect of PD (P = 0.8) or GHD (P = 0.23) on fatigue in SAH survivors over time.

CONCLUSIONS

Fatigue is a common symptom amongst SAH survivors. WFNS is a usable clinical determinant of fatigue in SAH survivors. Neither PD nor GHD has a significant effect on long-term fatigue after SAH.

Brain lesion correlates of fatigue in individuals with traumatic brain injury

The purpose of this study was to investigate the neurological correlates of both subjective fatigue as well as objective fatigability in individuals with traumatic brain injury (TBI). The study has a cross-sectional design. Participants (N = 53) with TBI (77% male, mean age at injury 38 years, mean time since injury 1.8 years) underwent a structural magnetic resonance imaging (MRI) scan and completed the Fatigue Severity Scale (FSS), while a subsample (N = 36) was also tested with a vigilance task. While subjective fatigue (FSS) was not related to measures of brain lesions, multilevel analyses showed that a change in the participants' decision time was significantly predicted by grey matter (GM) lesions in the right frontal lobe. The time-dependent development of the participants' error rate was predicted by total brain white matter (WM) lesion volumes, as well as right temporal GM and WM lesion volumes. These findings could be explained by decreased functional connectivity of attentional networks, which results in accelerated exhaustion during cognitive task performance. The disparate nature of objectively measurable fatigability on the one hand and the subjective experience of fatigue on the other needs further investigation.

Parkinson's disease-related fatigue: A case definition and recommendations for clinical research

Fatigue is one of the most common and disabling symptoms in Parkinson's disease (PD). Since fatigue was first described as a common feature of PD 20 years ago, little progress has been made in understanding its causes or treatment. Importantly, PD patients attending the 2013 World Parkinson Congress voted fatigue as the leading symptom in need of further research. In response, the Parkinson Disease Foundation and ProjectSpark assembled an international team of experts to create recommendations for clinical research to advance this field. The working group identified several areas in which shared standards would improve research quality and foster progress including terminology, diagnostic criteria, and measurement. Terminology needs to (1) clearly distinguish fatigue from related phenomena (eg, sleepiness, apathy, depression); (2) differentiate subjective fatigue complaints from objective performance fatigability; and (3) specify domains affected by fatigue and causal factors. We propose diagnostic criteria for PD-related fatigue to guide participant selection for clinical trials and add rigor to mechanistic studies. Recommendations are made for measurement of subjective fatigue complaints, performance fatigability, and neurophysiologic changes. We also suggest areas in which future research is needed to address methodological issues and validate or optimize current practices. Many limitations in current PD-related fatigue research may be addressed by improving methodological standards, many of which are already being successfully applied in clinical fatigue research in other medical conditions (eg, cancer, multiple sclerosis). © 2016 International Parkinson and Movement Disorder Society.

Strategies for Rapid Muscle Fatigue Reduction during FES Exercise in Individuals with Spinal Cord Injury: A Systematic Review

Background

Rapid muscle fatigue during functional electrical stimulation (FES)-evoked muscle contractions in individuals with spinal cord injury (SCI) is a significant limitation to attaining health benefits of FES-exercise. Delaying the onset of muscle fatigue is often cited as an important goal linked to FES clinical efficacy. Although the basic concept of fatigue-resistance has a long history, recent advances in biomedical engineering, physiotherapy and clinical exercise science have achieved improved clinical benefits, especially for reducing muscle fatigue during FES-exercise. This review evaluated the methodological quality of strategies underlying muscle fatigue-resistance that have been used to optimize FES therapeutic approaches. The review also sought to synthesize the effectiveness of these strategies for persons with SCI in order to establish their functional impacts and clinical relevance.

Methods

Published scientific literature pertaining to the reduction of FES-induced muscle fatigue was identified through searches of the following databases: Science Direct, Medline, IEEE Xplore, SpringerLink, PubMed and Nature, from the earliest returned record until June 2015. Titles and abstracts were screened to obtain 35 studies that met the inclusion criteria for this systematic review.

Results

Following the evaluation of methodological quality (mean (SD), 50 (6) %) of the reviewed studies using the Downs and Black scale, the largest treatment effects reported to reduce muscle fatigue mainly investigated isometric contractions of limited functional and clinical relevance (n = 28). Some investigations (n = 13) lacked randomisation, while others were characterised by small sample sizes with low statistical power. Nevertheless, the clinical significance of emerging trends to improve fatigue-resistance during FES included (i) optimizing electrode positioning, (ii) fine-tuning of stimulation patterns and other FES parameters, (iii) adjustments to the mode and frequency of exercise training, and (iv) biofeedback-assisted FES-exercise to promote selective recruitment of fatigue-resistant motor units.

Conclusion

Although the need for further in-depth clinical trials (especially RCTs) was clearly warranted to establish external validity of outcomes, current evidence was sufficient to support the validity of certain techniques for rapid fatigue-reduction in order to promote FES therapy as an integral part of SCI rehabilitation. It is anticipated that this information will be valuable to clinicians and other allied health professionals administering FES as a treatment option in rehabilitation and aid the development of effective rehabilitation interventions.

Fatigue in Parkinson's disease: report from a mutidisciplinary symposium

Fatigue is a severe problem for many people living with Parkinson's disease (PD). Best estimates suggest that more than 50% of patients experience this debilitating symptom. Little is known about its etiology or treatment, making the understanding of fatigue a true unmet need. As part of the Parkinson's Disease Foundation Community Choice Research Program, patients, caregivers, and scientists attended a symposium on fatigue on 16 and 17 October 2014. We present a summary of that meeting, reviewing what is known about the diagnosis and treatment of fatigue, its physiology, and what we might learn from multiple sclerosis (MS), depression, and cancer-disorders in which fatigue figures prominently too. We conclude with focused recommendations to enhance our understanding and treatment of this prominent problem in PD.