The presence of attentional and interpretation biases in patients with severe MS-related fatigue.

OBJECTIVE: Severe fatigue is a prevalent and disabling symptom in multiple sclerosis (MS). This study tested if a fatigue- and physical activity-related attentional bias (AB) and a somatic interpretation bias (IB) are present in severely fatigued patients with MS. Biases were compared to healthy controls and patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). METHOD: Severely fatigued patients with MS or ME/CFS and healthy controls completed a Visual Probe Task (VPT) assessing fatigue- and physical activity-related AB and an IB task that assesses the tendency to interpret ambiguous information in either a somatically threatening way or in a more neutral manner. The VPT was completed by 38 MS patients, 44 ME/CFS patients, and 46 healthy controls; the IB task was completed by 156, 40 and 46 participants respectively. RESULTS: ANOVA showed no statistically significant group differences in a fatigue-related AB or physical activity-related AB (omnibus test of interaction between topic × condition: F2,125 = 1.87; p = .159). Both patient groups showed a tendency to interpret ambiguous information in a somatically threatening way compared to healthy controls (F1,2 = 27.61, p < .001). This IB was significantly stronger in MS patients compared to ME/CFS patients. IB was significantly correlated with cognitive responses to symptoms in MS patients. CONCLUSION: MS patients tend to interpret ambiguous information in a somatically threatening way. This may feed into unhelpful ways of dealing with symptoms, possibly contributing to the perpetuation of severe fatigue in MS.

Disentangling pain and fatigue in chronic fatigue syndrome: a resting state connectivity study before and after cognitive behavioral therapy.

BACKGROUND: Fatigue is a central feature of myalgic encephalomyelitis or chronic fatigue syndrome (ME/CFS), but many ME/CFS patients also report comorbid pain symptoms. It remains unclear whether these symptoms are related to similar or dissociable brain networks. This study used resting-state fMRI to disentangle networks associated with fatigue and pain symptoms in ME/CFS patients, and to link changes in those networks to clinical improvements following cognitive behavioral therapy (CBT). METHODS: Relationships between pain and fatigue symptoms and cortico-cortical connectivity were assessed within ME/CFS patients at baseline (N = 72) and after CBT (N = 33) and waiting list (WL, N = 18) and compared to healthy controls (HC, N = 29). The analyses focused on four networks previously associated with pain and/or fatigue, i.e. the fronto-parietal network (FPN), premotor network (PMN), somatomotor network (SMN), and default mode network (DMN). RESULTS: At baseline, variation in pain and fatigue symptoms related to partially dissociable brain networks. Fatigue was associated with higher SMN-PMN connectivity and lower SMN-DMN connectivity. Pain was associated with lower PMN-DMN connectivity. CBT improved SMN-DMN connectivity, compared to WL. Larger clinical improvements were associated with larger increases in frontal SMN-DMN connectivity. No CBT effects were observed for PMN-DMN or SMN-PMN connectivity. CONCLUSIONS: These results provide insight into the dissociable neural mechanisms underlying fatigue and pain symptoms in ME/CFS and how they are affected by CBT in successfully treated patients. Further investigation of how and in whom behavioral and biomedical treatments affect these networks is warranted to improve and individualize existing or new treatments for ME/CFS.