Chronic fatigue syndrome: the fundamentals still apply

Can sustained arousal explain the Chronic Fatigue Syndrome?

We present an integrative model of disease mechanisms in the Chronic Fatigue Syndrome (CFS), unifying empirical findings from different research traditions. Based upon the Cognitive activation theory of stress (CATS), we argue that new data on cardiovascular and thermoregulatory regulation indicate a state of permanent arousal responses - sustained arousal - in this condition. We suggest that sustained arousal can originate from different precipitating factors (infections, psychosocial challenges) interacting with predisposing factors (genetic traits, personality) and learned expectancies (classical and operant conditioning). Furthermore, sustained arousal may explain documented alterations by establishing vicious circles within immunology (Th2 (humoral) vs Th1 (cellular) predominance), endocrinology (attenuated HPA axis), skeletal muscle function (attenuated cortical activation, increased oxidative stress) and cognition (impaired memory and information processing). Finally, we propose a causal link between sustained arousal and the experience of fatigue. The model of sustained arousal embraces all main findings concerning CFS disease mechanisms within one theoretical framework.

Intracellular immune dysfunction in myalgic encephalomyelitis/chronic fatigue syndrome: state of the art and therapeutic implications

BACKGROUND

Evidence in support of intracellular immune dysfunctions in people with myalgic encephalomyelitis (ME)/chronic fatigue syndrome (CFS) is accumulating, but few studies have addressed intracellular immunity as a potential therapeutic target.

OBJECTIVE

To provide an overview of our present understanding of intracellular immunity in ME/CFS, to relate the intracellular immune dysfunctions to other aspects of the illness like decreased natural killer cell function, the presence of infections and poor exercise performance, and to point to potential therapeutic targets.

METHODS

An in-depth review of the scientific literature of intracellular immunity in people with ME/CFS was performed.

RESULTS/CONCLUSION

From the scientific literature it is concluded that proteolytic cleavage of the native RNase L enzyme is characteristic of the dysregulation of intracellular immunity in people with ME/CFS, but the origin of the dysregulation is speculative. There is increasing evidence for immune cell apoptosis and upregulation of various aspects of the 2'-5' oligoadenylate (2-5A) synthetase/RNase L pathway in ME/CFS. This review provides the theoretical rationale for conducting studies examining the effectiveness of direct or indirect drug targeting of the 2-5A synthetase/RNase L pathway in ME/CFS patients.

Chronic fatigue syndrome: a systematic review

OBJECTIVE

A systematic review of the literature about chronic fatigue syndrome (CFS).

METHODS

A search of the Medline database (via Ovid and PubMed) with the key words chronic fatigue syndrome, diagnosis, classification, epidemiology, etiology, physiopathology, metabolism, microbiology, immunology, virology, psychology, drug therapy, rehabilitation, and therapy. The reference lists of each article were examined for additional related articles.

RESULTS

CFS was defined in 1988 by the US Centes for Disease Control and Prevention. The prevalence of chronic fatigue syndrome has ranged from 0.2% to 0.7% in the general population. In 1994, the definition of CFS was revised by Fukuda et al. Despite various research in several topics (e.g. infection, immune systems, neuroendocrinology, autonomic activity, neuromuscular involvement), the pathophysiology remains unknown.

CONCLUSION

CFS, with its various major clinical and functional impacts, should be associated with a "biopsychosocial model". Progressive muscular rehabilitation, combined with behavioral and cognitive treatment, is an essential part of therapy.

Validation of the French 'multidimensional fatigue inventory' (MFI 20)

Fatigue has become an important symptom in research and also for clinical diagnosis and follow up. Many physical illnesses, in particular chronic ones such as cancer, are highly associated with fatigue. Various questionnaires for measuring fatigue have been developed, but currently no validated questionnaire exists in French language. We selected the 'Multidimensional Fatigue Inventory' (MFI) which has been validated in its English version and then translated into French by the designers. This study describes the validation step of the French version of MFI and presents the psychometric properties of this instrument. A sample of 225 patients was divided into three groups 'Tired' (82 subjects), 'Moderately tired' (36) and 'Not tired' (107). The analysis of the structure validity found four dimensions: 'General Fatigue', 'Mental Fatigue', 'Reduced Activities' and 'Motivation'. The convergent validity showed highly significant correlation (P < 0.001) with a visual analogue scale. The French MFI has been able to distinguish patients with different fatigue levels. Cronbach's alpha measurement of the scale and the subscales are good, cronbach alpha > 0.70. The reproducibility and sensitivity to change in patients who were followed up one month later show satisfactory results. This validation study of the French version of MFI shows that this instrument is valid for clinical application and allows different dimensions of fatigue to be assessed which is of particular interest for physicians, especially for cancer carers, where fatigue assessment is an important aspect of the follow up.