Pain in chronic fatigue syndrome: response to rehabilitative treatments in the PACE trial

A scoping review of 'Pacing' for management of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): lessons learned for the long COVID pandemic

BACKGROUND

Controversy over treatment for people with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a barrier to appropriate treatment. Energy management or pacing is a prominent coping strategy for people with ME/CFS. Whilst a definitive definition of pacing is not unanimous within the literature or healthcare providers, it typically comprises regulating activity to avoid post exertional malaise (PEM), the worsening of symptoms after an activity. Until now, characteristics of pacing, and the effects on patients' symptoms had not been systematically reviewed. This is problematic as the most common approach to pacing, pacing prescription, and the pooled efficacy of pacing was unknown. Collating evidence may help advise those suffering with similar symptoms, including long COVID, as practitioners would be better informed on methodological approaches to adopt, pacing implementation, and expected outcomes.

OBJECTIVES

In this scoping review of the literature, we aggregated type of, and outcomes of, pacing in people with ME/CFS.

ELIGIBILITY CRITERIA

Original investigations concerning pacing were considered in participants with ME/CFS.

SOURCES OF EVIDENCE

Six electronic databases (PubMed, Scholar, ScienceDirect, Scopus, Web of Science and the Cochrane Central Register of Controlled Trials [CENTRAL]) were searched; and websites MEPedia, Action for ME, and ME Action were also searched for grey literature, to fully capture patient surveys not published in academic journals.

METHODS

A scoping review was conducted. Review selection and characterisation was performed by two independent reviewers using pretested forms.

RESULTS

Authors reviewed 177 titles and abstracts, resulting in 17 included studies: three randomised control trials (RCTs); one uncontrolled trial; one interventional case series; one retrospective observational study; two prospective observational studies; four cross-sectional observational studies; and five cross-sectional analytical studies. Studies included variable designs, durations, and outcome measures. In terms of pacing administration, studies used educational sessions and diaries for activity monitoring. Eleven studies reported benefits of pacing, four studies reported no effect, and two studies reported a detrimental effect in comparison to the control group.

CONCLUSIONS

Highly variable study designs and outcome measures, allied to poor to fair methodological quality resulted in heterogenous findings and highlights the requirement for more research examining pacing. Looking to the long COVID pandemic, our results suggest future studies should be RCTs utilising objectively quantified digitised pacing, over a longer duration of examination (i.e. longitudinal studies), using the core outcome set for patient reported outcome measures. Until these are completed, the literature base is insufficient to inform treatment practises for people with ME/CFS and long COVID.

Brainstem volume changes in myalgic encephalomyelitis/chronic fatigue syndrome and long COVID patients

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and long COVID patients have overlapping neurological, autonomic, pain, and post-exertional symptoms. We compared volumes of brainstem regions for 10 ME/CFS (CCC or ICC criteria), 8 long COVID (WHO Delphi consensus), and 10 healthy control (HC) subjects on 3D, T1-weighted MRI images acquired using sub-millimeter isotropic resolution using an ultra-high field strength of 7 Tesla. Group comparisons with HC detected significantly larger volumes in ME/CFS for pons (p = 0.004) and whole brainstem (p = 0.01), and in long COVID for pons (p = 0.003), superior cerebellar peduncle (p = 0.009), and whole brainstem (p = 0.005). No significant differences were found between ME/CFS and long COVID volumes. In ME/CFS, we detected positive correlations between the pons and whole brainstem volumes with "pain" and negative correlations between the midbrain and whole brainstem volumes with "breathing difficulty." In long COVID patients a strong negative relationship was detected between midbrain volume and "breathing difficulty." Our study demonstrated an abnormal brainstem volume in both ME/CFS and long COVID consistent with the overlapping symptoms.

Clinical overlap between fibromyalgia and myalgic encephalomyelitis. A systematic review and meta-analysis

Myalgic encephalomyelitis is an illness characterized by profound malaise after mental or physical effort occurring in patients already suffering from constant fatigue. On the other hand, widespread pain and widespread allodynia are the core fibromyalgia clinical features. There is controversy on these two syndromes alikeness. Through the years, different diagnostic and/or classification criteria have been put forward to appraise both fibromyalgia and myalgic encephalomyelitis. The epidemiology of these two illnesses, and their overlap, may vary accordingly to the used definition. The most recent Wolfe et al. 2016 fibromyalgia diagnostic criteria incorporates three myalgic encephalomyelitis features including fatigue, waking unrefreshed and dyscognition. The objective of this meta-analysis was to define the clinical overlap between fibromyalgia and myalgic encephalomyelitis based on a systematic literature review.

METHODS

PubMed, Embase, Lilacs, and Cochrane data bases were searched on January 25, 2021 linking the medical subject heading "Fibromyalgia" to the following terms "chronic fatigue syndrome", "myalgic encephalomyelitis" and "systemic exertion intolerance disease". Our review included all original articles in which the clinical overlap between fibromyalgia and myalgic encephalomyelitis could be quantified based on recognized diagnostic or classification criteria. Articles scrutiny and selection followed the PRISMA guidelines. Each study quality was assessed according to GRADE recommendations. The global clinical overlap was calculated using a fixed effect model with inverse variance-weighted average method.

RESULTS

Twenty one publications were included in the meta-analysis. Reviewed studies were highly dissimilar in their design, objectives, sample size, diagnostic criteria, and/or outcomes yielding a 98% heterogeneity index. Nevertheless, the clinical overlap between fibromyalgia and myalgic encephalomyelitis was a well defined outcome that could be reliably calculated despite the high heterogeneity value. All reviewed publications had moderate GRADE evidence level. Most evaluated articles used the old 1990 Wolfe et al. fibromyalgia diagnostic criteria. Myalgic encephalomyelitis and fibromyalgia diagnoses overlapped in 47.3% (95% CI: 45.97-48.63) of the reported cases.

CONCLUSION

This meta-analysis found prominent clinical overlap between fibromyalgia and myalgic encephalomyelitis. It seems likely that this concordance would be even higher when using the most recent Wolfe et al. 2016 fibromyalgia diagnostic criteria.

Volumetric differences in hippocampal subfields and associations with clinical measures in myalgic encephalomyelitis/chronic fatigue syndrome

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) patients suffer from a cognitive and memory dysfunction. Because the hippocampus plays a key role in both cognition and memory, we tested for volumetric differences in the subfields of the hippocampus in ME/CFS. We estimated hippocampal subfield volumes for 25 ME/CFS patients who met Fukuda criteria only (ME/CFS_Fukuda), 18 ME/CFS patients who met the stricter ICC criteria (ME/CFS_ICC), and 25 healthy controls (HC). Group comparisons with HC detected extensive differences in subfield volumes in ME/CFS_ICC but not in ME/CFS_Fukuda. ME/CFS_ICC patients had significantly larger volume in the left subiculum head (p < 0.001), left presubiculum head (p = 0.0020), and left fimbria (p = 0.004). Correlations of hippocampus subfield volumes with clinical measures were stronger in ME/CFS_ICC than in ME/CFS_Fukuda patients. In ME/CFS_Fukuda patients, we detected positive correlations between fatigue and hippocampus subfield volumes and a negative correlation between sleep disturbance score and the right CA1 body volume. In ME/CFS_ICC patients, we detected a strong negative relationship between fatigue and left hippocampus tail volume. Strong negative relationships were also detected between pain and SF36 physical scores and two hippocampal subfield volumes (left: GC‐ML‐DG head and CA4 head). Our study demonstrated that volumetric differences in hippocampal subfields have strong statistical inference for patients meeting the ME/CFS_ICC case definition and confirms hippocampal involvement in the cognitive and memory problems of ME/CFS_ICC patients.

"Pacing does help you get your life back": The acceptability of a newly developed activity pacing framework for chronic pain/fatigue

OBJECTIVES

We have developed and feasibility tested an activity pacing framework for clinicians to standardise their recommendations of activity pacing to patients with chronic pain/fatigue. This study aimed to explore the acceptability and fidelity to this framework in preparation for a future trial of activity pacing.

DESIGN

Acceptability and fidelity were explored using semi-structured interviews. Data were analysed using framework analysis.

PARTICIPANTS

Patients who attended a rehabilitation programme for chronic pain/fatigue underpinned by the framework, and clinicians (physiotherapists and psychological wellbeing practitioners) who led the programmes.

RESULTS

Seventeen interviews were conducted, involving 12 patients with chronic pain/fatigue and five clinicians. The framework analysis revealed four deductive themes: (1) Acceptability of the activity pacing framework, (2) Acceptability of the feasibility study methods, (3) Processes of change and (4) Barriers and facilitators to activity pacing; and one inductive theme: (5) Perspectives of patients and clinicians.

CONCLUSIONS

The activity pacing framework appeared acceptable to patients and clinicians, and adherence to the framework was demonstrated. Processes of behaviour change included patients' regulation of activities through activity pacing. Barriers to pacing included work/social commitments and facilitators included identifying the benefits of pacing on symptoms. Different perspectives emerged between clinicians and patients regarding interpretations of symptom-contingent and quota-contingent strategies. The framework recognises fluctuations in symptoms of chronic pain/fatigue and encourages a quota-contingent approach with flexibility. Future work will develop a patient friendly guide ahead of a clinical trial to explore the effects of pacing.

The evidence base for physiotherapy in myalgic encephalomyelitis/chronic fatigue syndrome when considering post-exertional malaise: a systematic review and narrative synthesis

BACKGROUND

Due to the inconsistent use of diagnostic criteria in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), it is unsure whether physiotherapeutic management regarded effective in ME/CFS is appropriate for patients diagnosed with criteria that consider post-exertional malaise (PEM) as a hallmark feature.

PURPOSE

To appraise current evidence of the effects of physiotherapy on symptoms and functioning in ME/CFS patients in view of the significance of PEM in the applied diagnostic criteria for inclusion.

METHODS

A systematic review of randomized controlled trials published over the last two decades was conducted. Studies evaluating physiotherapeutic interventions for adult ME/CFS patients were included. The diagnostic criteria sets were classified into three groups according to the extent to which the importance of PEM was emphasized: chronic fatigue (CF; PEM not mentioned as a criterion), CFS (PEM included as an optional or minor criterion) or ME (PEM is a required symptom). The main results of included studies were synthesized in relation to the classification of the applied diagnostic criteria. In addition, special attention was given to the tolerability of the interventions.

RESULTS

Eighteen RCTs were included in the systematic review: three RCTs with CF patients, 14 RCTs with CFS patients and one RCT covering ME patients with PEM. Intervention effects, if any, seemed to disappear with more narrow case definitions, increasing objectivity of the outcome measures and longer follow-up.

CONCLUSION

Currently, there is no scientific evidence when it comes to effective physiotherapy for ME patients. Applying treatment that seems effective for CF or CFS patients may have adverse consequences for ME patients and should be avoided.

Music-based interventions to improve fibromyalgia syndrome: A meta-analysis

OBJECTIVE

We evaluated the effects of music therapy on pain, depression and quality of life in patients with fibromyalgia.

METHODS

Ten online databases were searched to identify randomized controlled trials that investigated the effects of music therapy on fibromyalgia patients, published up to 1st January 2019. The results were filtered and independently extracted. Statistical heterogeneity was assessed using the chi-square test. According to the outcome of the heterogeneity indices, either a fixed effect or a random effect model was used.

RESULTS

In total, seven randomized controlled trials were included. The Pain Visual Analog Scale, the McGill Pain Scale, the Beck Depression Scale and the Fibromyalgia Impact Questionnaire were used as outcome measures. Our evidence indicated that patient intervention with music therapy had lower scores on the Pain Visual Analog Scale (95% confidence interval [CI] -2.22 to -1.18, Z = 6.44, P < 0.00001, four studies) and Beck Depression Scale (95% CI -0.65 to -0.03, Z = 2.17, P = 0.03, two studies). No significant differences were observed on the McGill Pain Scale between the music intervention and control groups (95% CI -0.83 to -0.09, Z = 1.59, P = 0.11). A general qualitative description of the Fibromyalgia Impact Questionnaire results was given due to high heterogeneity (I² = 96%, P < 0.00001).

CONCLUSIONS

The music therapy is superior to non-music therapy in the treatment of pain, depression, and improvement of quality of life in fibromyalgia patients. However, due to the low quantity and quality of the included studies, a larger number and high-quality of RCTs are needed to confirm the beneficial effects of music therapy.

Learned pacing for adults with chronic pain: A randomised controlled trial feasibility study

INTRODUCTION

Chronic pain can significantly impact on an individual's occupational performance and quality of life. Pacing is a pain management strategy regularly used in occupational therapy practice; however, evidence for its effectiveness has not been established.

OBJECTIVES

To determine the feasibility of a future randomised controlled trial to investigate the effectiveness of a learned pacing intervention on occupational performance and satisfaction for adults with chronic pain.

METHODS

A randomised controlled trial feasibility study was conducted with participants randomly assigned to a learned pacing intervention or a waitlist control group. The primary outcome measure was the Canadian Occupational Performance Measure.

RESULTS

One hundred and twenty-eight people were screened for eligibility over 36 weeks, with 74 people invited to participate. Twelve were randomly assigned, eight to the learned pacing group and four to the control group. Those receiving the learned pacing intervention had clinically important changes in occupational performance and occupational satisfaction. Participants in the waitlist control group also had clinically important changes in occupational satisfaction. The method design was deemed feasible; however, several improvements would increase the rate of participant recruitment and reduce attrition. Recruitment from multiple sites is required to obtain an adequate sample size of 60.

CONCLUSION

Undertaking a future randomised controlled trial is feasible and warranted to establish the effectiveness of a learned pacing intervention on occupational performance and satisfaction for adults with chronic pain.

Effectiveness of Pacing as a Learned Strategy for People With Chronic Pain: A Systematic Review

Importance: Pacing is a key pain management strategy used by occupational therapy practitioners when working with people with chronic pain. However, there is a paucity of evidence and a lack of consensus regarding the effectiveness of pacing as a pain management strategy for people with chronic pain.

Objective: To evaluate the evidence for the effectiveness of pacing as a learned strategy for people with chronic pain.

Data Sources: Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were used to undertake a systematic review. Six databases were searched in March 2016 for randomized controlled trials (RCTs). Combinations of keywords and MeSH terms were used as search terms.

Study Selection and Data Collection: We sought intervention studies that included participants using pacing as a strategy. Studies were assessed for eligibility on the basis of predetermined criteria. Of the 2,820 articles located, 7 RCTs met inclusion criteria.

Findings: Pacing does not reduce the severity of pain or alter psychological traits; however, it can assist in lessening joint stiffness and the interference of fatigue and in decreasing the variability of physical activity.

Conclusions and Relevance: Current evidence supports the delivery of a learned pacing intervention to reduce the interference of fatigue, reduce joint stiffness, and decrease physical activity variability but does not support the use of learned pacing to reduce pain severity. Future research should investigate the effectiveness of pacing as a pain management strategy within the International Classification of Functioning, Disability and Health domains of activity and participation.

What This Article Adds: This systematic review examines existing research on pacing as a learned intervention strategy. The findings will support the clinical reasoning of occupational therapy practitioners, to determine when a learned pacing strategy is indicated, and considerations for how it may be delivered.

Operant Learning Versus Energy Conservation Activity Pacing Treatments in a Sample of Patients With Fibromyalgia Syndrome: A Pilot Randomized Controlled Trial

This study's aim was to assess the efficacy of 2 forms of activity pacing in patients with fibromyalgia syndrome (FMS). Treatment-related changes in activity management patterns were also examined. Patients with FMS (n = 178) were randomly assigned to an operant learning (OL; delayed [n = 36] or immediate [n = 54] groups) or an energy conservation (EC; delayed [n = 35] or immediate [n = 53] groups) treatment condition. Of these, 32 OL and 37 EC patients completed treatment. Forty-three patients were allocated to the delayed treatment condition (control group). Repeated measures analyses of variance were used to examine the effects of OL and EC treatments on primary (average pain and usual fatigue), secondary (pain and fatigue interference, physical and psychological function, sleep quality, depressive symptoms, and anxiety symptoms), and tertiary (pain-related activity patterns) outcomes. Neither treatment was effective in reducing average pain or usual fatigue symptoms. Relative to EC, OL patients showed greater improvements in depressive symptoms, whereas nonsignificant trends (P values ranging between .05 and .06) were observed for pain interference, fatigue interference, and psychological function. Both treatments were associated with improvements in sleep quality and physical function, increases in pacing, and decreases in overdoing activity patterns. Reductions in activity avoidance were only found in OL. These findings suggest that OL may be more beneficial than EC and that it could potentially be viewed as an effective stand-alone activity pacing treatment for patients with FMS. Research to determine the extent to which these preliminary findings replicate is warranted. PERSPECTIVE: This article examines the efficacy of 2 forms of activity pacing in patients with fibromyalgia syndrome. The results suggest the possibility that operant learning may be more beneficial than energy conservation and could potentially be viewed as an effective stand-alone activity pacing treatment for patients with fibromyalgia syndrome.

Fatigue symptoms in relation to neuroticism, anxiety-depression, and musculoskeletal pain. A longitudinal twin study

BACKGROUND

The nature of the relationship between fatigue and its risk factors is poorly understood. In the present study the genetic and environmental association between anxiety-depression, musculoskeletal (MS) pain and fatigue was examined, and the role of neuroticism as a shared risk factor that may possibly explain the co-occurrence between these phenotypes was investigated in a combined cross-sectional and longitudinal twin design.

METHODS

The sample consisted of 746 monozygotic (MZ) and 770 dizygotic (DZ) twins in the age group of 50-65 (mean = 57.11 years, SD = 4.5). Continuous measures of fatigue symptoms and the other phenotypes were employed. Using Cholesky modeling, genetic and environmental influences on the phenotypes, and the associations among them, were determined. Analyses were performed using measures of neuroticism obtained concurrently and 13-19 years earlier.

RESULTS

Results from multiple regression analyses showed that neuroticism, anxiety-depression symptoms, and MS pain were all significantly associated with fatigue, controlling for sex, education, and general health indices. The best-fitting biometric models included additive genetic and individual-specific environmental effects. Heritabilities in the 0.40-0.53 range were demonstrated. Furthermore, while there was a considerable overlap in genetic risk factors between the four phenotypes, a substantial proportion of the genetic risk shared between anxiety-depression and fatigue, and between MS pain and fatigue, was independent of neuroticism.

CONCLUSION

Evidence for a common underlying susceptibility to report fatigue symptoms, genetically linked to neuroticism, anxiety-depression, and MS pain, was found. Both unique and pleiotropic effects appear to be involved in the genetic architecture of the phenotypes.

Treating patients suffering from myalgic encephalopathy/chronic fatigue syndrome (ME/CFS) with sodium dichloroacetate: An open-label, proof-of-principle pilot trial

Twenty-two consecutive patients suffering from refractory myalgic encephalitis/chronic fatigue syndrome (ME/CFS) were treated with an innovative nutriceutical containing sodium dichloroacetate in a proof-of-principle, pilot, open-label prospective cohort trial. Ten patients experienced significant improvement of their health condition with reduction to almost half of their score in the fatigue severity scale. In twelve patients treatment failed to exert any beneficial effect. In the latter patients several other diseases have commonly been revealed by extensive biological and imaging investigations. These preliminary findings sustain the hypothetical role of mitochondrial hypo-metabolism due to inhibition of the activity of the pyruvate dehydrogenase in the pathogenesis of primary ME/CFS, and suggest a possible benefit of nutriceutical treatment by sodium dichloroacetate.

Symptoms of chronic fatigue syndrome/myalgic encephalopathy are not determined by activity pacing when measured by the chronic pain coping inventory

OBJECTIVES

Chronic fatigue syndrome/myalgic encephalopathy (CFS/ME) is a chronic illness which can cause significant fatigue, pain and disability. Activity pacing is frequently advocated as a beneficial coping strategy, however, it is unclear whether pacing is significantly associated with symptoms in people with CFS/ME. The first aim of this study was therefore to explore the cross-sectional associations between pacing and levels of pain, disability and fatigue. The second aim was to explore whether changes in activity pacing following participation in a symptom management programme were related to changes in clinical outcomes.

DESIGN

Cross-sectional study exploring the relationships between pacing, pain, disability and fatigue (n=114) and pre-post treatment longitudinal study of a cohort of patients participating in a symptom management programme (n=35).

SETTING

Out-patient physiotherapy CFS/ME service.

PARTICIPANTS

One-hundred and fourteen adult patients with CFS/ME.

MAIN OUTCOME MEASURES

Pacing was assessed using the chronic pain coping inventory. Pain was measured using a Numeric Pain Rating Scale, fatigue with the Chalder Fatigue Scale and disability with the Fibromyalgia Impact Questionnaire.

RESULTS

No significant associations were observed between activity pacing and levels of pain, disability or fatigue. Likewise, changes in pacing were not significantly associated with changes in pain, disability or fatigue following treatment.

CONCLUSIONS

Activity pacing does not appear to be a significant determinant of pain, fatigue or disability in people with CFS/ME when measured with the chronic pain coping index. Consequently, the utility and measurement of pacing require further investigation.

Activity patterns in response to symptoms in patients being treated for chronic fatigue syndrome: An experience sampling methodology study

OBJECTIVE

Cognitive-behavioral models of chronic fatigue syndrome (CFS) propose that patients respond to symptoms with 2 predominant activity patterns-activity limitation and all-or-nothing behaviors-both of which may contribute to illness persistence. The current study investigated whether activity patterns occurred at the same time as, or followed on from, patient symptom experience and affect.

METHOD

Twenty-three adults with CFS were recruited from U.K. CFS services. Experience sampling methodology (ESM) was used to assess fluctuations in patient symptom experience, affect, and activity management patterns over 10 assessments per day for a total of 6 days. Assessments were conducted within patients' daily life and were delivered through an app on touchscreen Android mobile phones. Multilevel model analyses were conducted to examine the role of self-reported patient fatigue, pain, and affect as predictors of change in activity patterns at the same and subsequent assessment.

RESULTS

Current experience of fatigue-related symptoms and pain predicted higher patient activity limitation at the current and subsequent assessments whereas subjective wellness predicted higher all-or-nothing behavior at both times. Current pain predicted less all-or-nothing behavior at the subsequent assessment. In contrast to hypotheses, current positive affect was predictive of current activity limitation whereas current negative affect was predictive of current all-or-nothing behavior. Both activity patterns varied at the momentary level.

CONCLUSIONS

Patient symptom experiences appear to be driving patient activity management patterns in line with the cognitive-behavioral model of CFS. ESM offers a useful method for examining multiple interacting variables within the context of patients' daily life. (PsycINFO Database Record

Prefrontal Structure Varies as a Function of Pain Symptoms in Chronic Fatigue Syndrome

BACKGROUND

Chronic fatigue syndrome (CFS) is characterized by severe fatigue persisting for ≥6 months and leading to considerable impairment in daily functioning. Neuroimaging studies of patients with CFS have revealed alterations in prefrontal brain morphology. However, it remains to be determined whether these alterations are specific for fatigue or whether they relate to other common CFS symptoms (e.g., chronic pain, lower psychomotor speed, and reduced physical activity).

METHODS

We used magnetic resonance imaging to quantify gray matter volume (GMV) and the N-acetylaspartate and N-acetylaspartylglutamate/creatine ratio (NAA/Cr) in a group of 89 women with CFS. Building on previous reports, we tested whether GMV and NAA/Cr in the dorsolateral prefrontal cortex are associated with fatigue severity, pain, psychomotor speed, and physical activity, while controlling for depressive symptoms. We also considered GMV and NAA/Cr differences between patients with CFS and 26 sex-, age-, and education-matched healthy controls.

RESULTS

The presence of pain symptoms was the main predictor of both GMV and NAA/Cr in the left dorsolateral prefrontal cortex of patients with CFS. More pain was associated with reduced GMVs and NAA/Cr, over and above the effects of fatigue, depressive symptoms, physical activity, and psychomotor speed. In contrast to previous reports and despite a large representative sample, global GMV did not differ between the CFS and healthy control groups.

CONCLUSIONS

CFS, as diagnosed by Centers for Disease Control and Prevention criteria, is not a clinical entity reliably associated with reduced GMV. Individual variation in the presence of pain, rather than fatigue, is associated with neuronal alterations in the dorsolateral prefrontal cortex of patients with CFS.

The role of the hippocampus in the pathogenesis of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a severe acquired illness characterized by a profound sensation of fatigue, not ameliorated by rest and resulting in a substantial decrease in the amount and quality of occupational, social and recreational activities. Despite intense research, the aetiology and pathogenesis of ME/CFS is still unknown and no conclusive biological markers have been found. As a consequence, an accepted curative treatment is still lacking and rehabilitation programmes are not very effective, as few patients recover. Increased knowledge of the mechanisms leading to the emergence and maintenance of the illness is called for. In this study, I will put forth an alternative hypothesis to explain some of the pathologies associated with ME/CFS, by concentrating on one of the major strategic organs of the brain, the hippocampus. I will show that the ME/CFS triggering factors also impact the hippocampus, leading to neurocognitive deficits and disturbances in the regulation of the stress system and pain perception. These deficits lead to a substantial decrease in activity and to sleep disorders, which, in turn, impact the hippocampus and initiate a vicious circle of increased disability.