Neuroaetiology of chronic fatigue syndrome: an overview

Abstract:

Chronic fatigue syndrome (CFS) is now recognized as a medial disorder. In contrast to recent related reports, the present review focuses primarily on aetiological aspects of CFS. Four major hypotheses are reviewed. (1) Although CFS is often associated with viral infection, the presence of viruses has as yet not consistently been detected. (2) It is not clear whether anomalies of the HPA axis often observed in CFS, are cause or the consequences of the disorder. (3) Immune dysfunction as the cause of CFS is thus far the weakest hypothesis. (4) The psychiatric and psychosocial hypothesis denies the existence of CFS as a disease entity. Accordingly, the fatigue symptoms are assumed to be the consequence of other (somatic) diseases. Other possible causes of CFS are oxidative stress and genetic predisposition. In CFS cognitive behavioural therapy is most commonly used. This therapy, however, appears to be ineffective in many patients. The suggested causes of CFS and the divergent reactions to therapy may be explained by the lack of recognition of subgroups. Identification of subtypes may lead to more effective therapeutic interventions.

 

Source: Sanders P, Korf J. Neuroaetiology of chronic fatigue syndrome: an overview. World J Biol Psychiatry. 2008;9(3):165-71. https://www.ncbi.nlm.nih.gov/pubmed/17853290

 

Higher heart rate and reduced heart rate variability persist during sleep in chronic fatigue syndrome: a population-based study

Abstract:

Autonomic nervous system (ANS) dysfunction has been suggested in patients with chronic fatigue syndrome (CFS). In this study, we sought to determine whether increased heart rate (HR) and reduced heart rate variability (HRV) parameters observed in CFS patients during wakefulness persist during sleep. To this end, we compared heart rate (HR) and HRV as indicators of ANS function in CFS subjects and non-fatigued (NF) controls in a population-based, case-control study.

Thirty subjects with CFS and 38 NF controls, matched for age-, sex- and body mass index, were eligible for analysis. Main outcome measures included mean RR interval (RRI), HR, and HRV parameters derived from overnight ECG. Plasma aldosterone and norepinephrine levels, medicines with cardiovascular effect, and reported physical activity were examined as covariates. General Linear Models were used to assess significance of associations and adjust for potential confounders.

Compared to controls, CFS cases had significantly higher mean HR (71.4 vs 64.8 bpm), with a shorter mean RRI [840.4 (85.3) vs 925.4(97.8) ms] (p<0.0004, each), and reduced low frequency (LF), very low frequency (VLF), and total power (TP) of HRV (p<0.02, all). CFS cases had significantly lower plasma aldosterone (p<0.05), and tended to have higher plasma norepinephrine levels. HR correlated weakly with plasma norepinephrine (r=0.23, p=0.05) and moderately with vitality and fatigue scores (r=-0.49 and 0.46, respectively, p<0.0001). Limitation in moderate physical activity was strongly associated with increased HR and decreased HRV. Nevertheless, among 42 subjects with similar physical activity limitations, CFS cases still had higher HR (71.8 bpm) than respective controls (64.9 bpm), p=0.023, suggesting that reduced physical activity could not fully explain CFS-associated differences in HR and HRV. After adjusting for potential confounders case-control differences in HR and TP remained significant (p<0.05).

CONCLUSION: The presence of increased HR and reduced HRV in CFS during sleep coupled with higher norepinephrine levels and lower plasma aldosterone suggest a state of sympathetic ANS predominance and neuroendocrine alterations. Future research on the underlying pathophysiologic mechanisms of the association is needed.

 

Source: Boneva RS, Decker MJ, Maloney EM, Lin JM, Jones JF, Helgason HG, Heim CM, Rye DB, Reeves WC. Higher heart rate and reduced heart rate variability persist during sleep in chronic fatigue syndrome: a population-based study. Auton Neurosci. 2007 Dec 30;137(1-2):94-101. Epub 2007 Sep 12. https://www.ncbi.nlm.nih.gov/pubmed/17851136

 

Open-label study of s-citalopram therapy of chronic fatigue syndrome and co-morbid major depressive disorder

Abstract:

OBJECTIVE: Chronic fatigue syndrome (CFS) is a debilitating disorder with prominent symptoms of malaise, fatigue, myalgia, arthralgia, and impaired concentration. The symptoms of CFS may often overlap those of Major Depressive Disorder (MDD). Treatment of CFS has generally been disappointing. We hypothesized that s-citalopram therapy may improve the symptoms of both disorders in CFS patients with co-morbid depression.

METHODS: 16 patients received s-citalopram 10 mg to 20 mg daily for up to 12 weeks. Outcome measures of CFS included the Chalder Fatigue Questionnaire (CFQ), the multi-dimensional Fatigue Impact Scale (FIS), the CFS symptom rating (CFS-SR) 100 mm visual analogue scale, and the clinical global impressions severity (CGI/S) and change (CGI/C) ratings. Secondary outcomes of MDD included the Hamilton Depression Rating (HAM-D), Beck Depression Inventory (BDI), and the CGI/S and CGI/C ratings of MDD.

RESULTS: We observed reductions in the mean CFQ score (p<0.0005), FIS score (p<0.0005), and CGI/S (p<0.0005) and CGI/C (p<0.0005) ratings over time. There was a significant improvement in 5 of the 8 CFS-SR symptoms: post-exertion malaise (p=0.001), headaches (p<0.0005), un-refreshing sleep (p<0.0005), and impaired memory and concentration (p<0.0005). There was also a reduction in mean HAM-D (p<0.0005), BDI (p<0.0005), CGI/S (p=0.001) and CGI/C (p<0.0005) ratings of MDD.

LIMITATIONS: The sample size was limited and the study design was not double-blind or placebo controlled.

CONCLUSION: We observed a significant reduction in both CFS and co-morbid MDD symptom severity ratings, and improvement in 5 of 8 core somatic symptoms of CFS during s-citalopram therapy.

 

Source: Amsterdam JD, Shults J, Rutherford N. Open-label study of s-citalopram therapy of chronic fatigue syndrome and co-morbid major depressive disorder. Prog Neuropsychopharmacol Biol Psychiatry. 2008 Jan 1;32(1):100-6. Epub 2007 Aug 3. https://www.ncbi.nlm.nih.gov/pubmed/17804135

 

Combined dexamethasone/corticotropin-releasing factor test in chronic fatigue syndrome

Abstract:

BACKGROUND: Studies of hypothalamic-pituitary-adrenal (HPA) axis function in chronic fatigue syndrome (CFS) point to hypofunction, although there are negative reports. Suggested mechanisms include a reduced hypothalamic or supra-hypothalamic stimulus to the HPA axis and enhanced sensitivity to the negative feedback of glucocorticoids. The aim of the current study was to investigate HPA axis function in CFS with the dexamethasone/corticotropin-releasing factor (Dex/CRF) test, in analogy with research in affective disorders.

METHOD: Thirty-four well-characterized female CFS patients and 25 healthy control subjects participated in the low-dose Dex/CRF test. Current major depressive episode was an exclusion criterion. History of early-life stress (ELS) was assessed with the Structured Trauma Interview.

RESULTS: Salivary cortisol responses after 0.5 mg Dex were lower in CFS patients than in controls (before 100 microg CRF, p=0.038; after 100 microg CRF, p=0.015). A secondary analysis revealed an influence of early-life stress and of oestrogen intake. After removal of the 10 participants who were taking an oral oestrogen, patients without a history of ELS showed lower cortisol responses than patients with ELS and controls (before CRF, p=0.005; after CRF, p=0.008).

CONCLUSIONS: CFS is globally associated with reduced cortisol responses in the combined low-dose Dex/CRF test, but this effect is only clearly present in CFS patients without a history of ELS. This study provides further support for an enhanced glucocorticoid negative feedback and/or a reduced central HPA axis drive in CFS. Furthermore, it demonstrates that ELS is an important variable to consider in CFS research.

 

Source: Van Den Eede F, Moorkens G, Hulstijn W, Van Houdenhove B, Cosyns P, Sabbe BG, Claes SJ. Combined dexamethasone/corticotropin-releasing factor test in chronic fatigue syndrome. Psychol Med. 2008 Jul;38(7):963-73. Epub 2007 Sep 6. https://www.ncbi.nlm.nih.gov/pubmed/17803834

 

The chronic fatigue syndrome: a comparative pathway analysis

Abstract:

In this paper, we introduce a method to detect pathological pathways of a disease. We aim to identify biological processes rather than single genes affected by the chronic fatigue syndrome (CFS). So far, CFS has neither diagnostic clinical signals nor abnormalities that could be diagnosed by laboratory examinations. It is also unclear if the CFS represents one disease or can be subdivided in different categories. We use information from clinical trials, the gene ontology (GO) database as well as gene expression data to identify undirected dependency graphs (UDGs) representing biological processes according to the GO database. The structural comparison of UDGs of sick versus non-sick patients allows us to make predictions about the modification of pathways due to pathogenesis.

 

Source: Emmert-Streib F. The chronic fatigue syndrome: a comparative pathway analysis. J Comput Biol. 2007 Sep;14(7):961-72. https://www.ncbi.nlm.nih.gov/pubmed/17803373

 

Diagnosis and management of chronic fatigue syndrome or myalgic encephalomyelitis (or encephalopathy): summary of NICE guidance

Data from other countries indicate that chronic fatigue syndrome (also known as myalgic encephalomyelitis or myalgic encephalopathy) (CFS/ME) is relatively common (affecting at least 0.2-0.4% of the population), although good epidemiological data for the United Kingdom are lacking. Many different potential aetiologies for CFS/ME have been investigated, including neurological, endocrine, immunological, genetic, psychiatric, and infectious, but the aetiology cannot yet be fully explained. CFS/ME can cause prolonged illness and disability and substantially affect patients and their families. Although most patients have mild or moderate symptoms, some have severe CFS/ME and are housebound or even unable to move from their bed. Uncertainties about diagnosis and management may exacerbate the impact of symptoms, and patients often encounter delays in diagnosis and difficulty accessing information, support, and potentially helpful therapies.1 This article summarises the most recent guidance from the National Institute for Health and Clinical Excellence (NICE) on diagnosing and managing this condition.2

 

Source: Baker R, Shaw EJ. Diagnosis and management of chronic fatigue syndrome or myalgic encephalomyelitis (or encephalopathy): summary of NICE guidance. BMJ. 2007 Sep 1;335(7617):446-8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1962830/ (Full article)

 

Chronic fatigue syndrome or myalgic encephalomyelitis

Comment on: Diagnosis and management of chronic fatigue syndrome or myalgic encephalomyelitis (or encephalopathy): summary of NICE guidance. [BMJ. 2007]

The uncertainty inherent in making a diagnosis of chronic fatigue syndrome (CFS) is reflected by the variety of names (such as myalgic encephalomyelitis; ME) it has been given. The names reflect the hope that such labels can impose some certainty where little exists. Many doctors are reluctant to make a diagnosis of CFS, with half not even believing it exists.1 The consequences of this uncertainty and reluctance have been that patients hear mixed messages and often receive poor, if any, care.2 It is therefore a welcome relief that the National Institute for Health and Clinical Excellence (NICE) has just published clinical guidelines on the diagnosis and management of this disease.3 In this week’s BMJ, Baker and Shaw summarise the guidelines.4

You can read the rest of this comment here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1962896/

 

Source: White P, Murphy M, Moss J, Armstrong G, Spencer P. Chronic fatigue syndrome or myalgic encephalomyelitis. BMJ. 2007 Sep 1;335(7617):411-2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1962896/ (Full article)

 

Overlap between atypical depression, seasonal affective disorder and chronic fatigue syndrome

Abstract:

OBJECTIVE: We reviewed previous studies that have described an association between abnormal functioning of the hypothalamic-pituitary-adrenal axis and depression. In addition to melancholic depression, a spectrum of conditions may be associated with increased and prolonged activation of the hypothalamic-pituitary-adrenal axis. In contrast another group of states is characterized by hypoactivation of the stress system, rather than sustained activation, in which chronically reduced secretion of corticotropin releasing factor may result in pathological hypoarousal and an enhanced hypothalamic-pituitary-adrenal negative feedback. Patients with atypical depression, seasonal affective disorder and chronic fatigue syndrome fall in this category.

METHOD: The literature data on the overlap between the key-words were reviewed, summarized and discussed.

RESULTS: Many studies suggest that these conditions themselves overlap biologically, showing hypofunction of central corticotropin releasing factor neuronal systems.

CONCLUSIONS: Therefore, in the real world of clinical practice, patients often present in a grey area between classical idiopathic fatigue and early chronic atypical depression and/or seasonal depression. This underscores the potential common biological links underpinning common symptom clusters not only between depression (atypical and seasonal) and chronic fatigue syndrome, but also other conditions characterized by the hypothalamic-pituitary-adrenal axis mainly diminished the corticotropin releasing factor activity.

 

Source: Juruena MF, Cleare AJ. Overlap between atypical depression, seasonal affective disorder and chronic fatigue syndrome. Rev Bras Psiquiatr. 2007 May;29 Suppl 1:S19-26. [Article in Portuguese] http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-44462007000500005&lng=en&nrm=iso&tlng=en (Full article)

 

Hematologic and urinary excretion anomalies in patients with chronic fatigue syndrome

Abstract:

Patients with chronic fatigue syndrome (CFS) have a broad and variable spectrum of signs and symptoms with variable onsets. This report outlines the results of a single-blind, cross-sectional research project that extensively investigated a large cohort of 100 CFS patients and 82 non fatigued control subjects with the aim of performing a case-control evaluation of alterations in standard blood parameters and urinary amino and organic acid excretion profiles.

Blood biochemistry and full blood counts were unremarkable and fell within normal laboratory ranges. However, the case-control comparison of the blood cell data revealed that CFS patients had a significant decrease in red cell distribution width and increases in mean platelet volume, neutrophil counts, and the neutrophil-lymphocyte ratio.

Evaluation of the urine excretion parameters also revealed a number of anomalies. The overnight urine output and rate of amino acid excretion were both reduced in the CFS group (P < 0.01). Significant decreases in the urinary excretion of asparagine (P < 0.0001), phenylalanine (P < 0.003), the branch chain amino acids (P < 0.005), and succinic acid (P < 0.0001), as well as increases in 3-methylhistidine (P < 0.05) and tyrosine (P < 0.05) were observed.

It was concluded that the urinary excretion and blood parameters data supported the hypothesis that alterations in physiologic homeostasis exist in CFS patients.

 

Source: Niblett SH, King KE, Dunstan RH, Clifton-Bligh P, Hoskin LA, Roberts TK, Fulcher GR, McGregor NR, Dunsmore JC, Butt HL, Klineberg I, Rothkirch TB. Hematologic and urinary excretion anomalies in patients with chronic fatigue syndrome. Exp Biol Med (Maywood). 2007 Sep;232(8):1041-9. https://www.ncbi.nlm.nih.gov/pubmed/17720950

 

Hyperventilation in patients with chronic fatigue syndrome: the role of coping strategies

Abstract:

Hyperventilation has been suggested as a concomitant and possible maintaining factor that may contribute to the symptom pattern of chronic fatigue syndrome (CFS). Because patients accepting the illness and trying to live with it seem to have a better prognosis than patients chronically fighting it, we investigated breathing behavior during different coping response sets towards the illness in patients with CFS (N=30, CDC criteria).

Patients imagined a relaxation script (baseline), a script describing a coping response of hostile resistance, and a script depicting acceptance of the illness and its (future) consequences. During each imagery trial, end-tidal PCO2 (Handheld Capnograph, Oridion) was measured. After each trial, patients filled out a symptom checklist. Results showed low resting values of PetCO2 overall, while only imagery of hostile resistance triggered a decrease and deficient recovery of PetCO2. Also, more hyperventilation complaints and complaints of other origin were reported during hostile resistance imagery compared with acceptance and relaxation.

In conclusion, hostile resistance seems to trigger both physiological and symptom perception processes contributing to the clinical picture of CFS.

 

Source: Bogaerts K, Hubin M, Van Diest I, De Peuter S, Van Houdenhove B, Van Wambeke P, Crombez G, Van den Bergh O. Hyperventilation in patients with chronic fatigue syndrome: the role of coping strategies. Behav Res Ther. 2007 Nov;45(11):2679-90. Epub 2007 Jul 20. https://www.ncbi.nlm.nih.gov/pubmed/17719001