Chronic fatigue syndrome: a literature review from a physiatric perspective

The Impact of a Structured Exercise Programme upon Cognitive Function in Chronic Fatigue Syndrome Patients

BACKGROUND

Cognitive function disturbance is a frequently described symptom of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). In this study, the effects of a structured exercise programme (SEP) upon cognitive function in ME/CFS patients was examined.

METHODS

Out of the 53 ME/CFS patients initiating SEP 34 (64%) completed the 16 week programme. Cognitive function was assessed using a computerized battery test consisting of a Simple Reaction Time (SRT) (repeated three times) and Choice Reaction Time (CRT) measurements, a Visual Attention Test (VAT) and a Delayed Matching to Sample (DMS) assessment.

RESULTS

Statistically significant improvement was noted in the third attempt to SRT in reaction time for correct answers, p = 0.045, r = 0.24. Moreover, significant improvement was noted in VAT reaction time, number of correct answers and errors committed, p = 0.02, omega = 0.03, p = 0.007, r = 0.34 and p = 0.004, r = 0.35, respectively. Non-significant changes were noted in other cognitive tests.

CONCLUSIONS

A substantial number of participants were unwilling or unable to complete the exercise programme. ME/CFS patients able to complete the SEP showed improved visual attention both in terms of reaction time and correctness of responses and processing speed of simple visual stimuli.

Phenylephrine alteration of cerebral blood flow during orthostasis: effect on n-back performance in chronic fatigue syndrome

Chronic fatigue syndrome (CFS) with orthostatic intolerance is characterized by neurocognitive deficits and impaired working memory, concentration, and information processing. In CFS, upright tilting [head-up tilt (HUT)] caused decreased cerebral blood flow velocity (CBFv) related to hyperventilation/hypocapnia and impaired cerebral autoregulation; increasing orthostatic stress resulted in decreased neurocognition. We loaded the baroreflex with phenylephrine to prevent hyperventilation and performed n-back neurocognition testing in 11 control subjects and 15 CFS patients. HUT caused a significant increase in heart rate (109.4 ± 3.9 vs. 77.2 ± 1.6 beats/min, P < 0.05) and respiratory rate (20.9 ± 1.7 vs. 14.2 ± 1.2 breaths/min, P < 0.05) and decrease in end-tidal CO2 (ETCO2; 42.8 ± 1.2 vs. 33.9 ± 1.1 Torr, P < 0.05) in CFS vs. control. HUT caused CBFv to decrease 8.7% in control subjects but fell 22.5% in CFS. In CFS, phenylephrine prevented the HUT-induced hyperventilation/hypocapnia and the significant drop in CBFv with HUT (-8.1% vs. -22.5% untreated). There was no difference in control subject n-back normalized response time (nRT) comparing supine to HUT (106.1 ± 6.9 vs. 97.6 ± 7.1 ms at n = 4), and no difference comparing control to CFS while supine (97.1 ± 7.1 vs 96.5 ± 3.9 ms at n = 4). However, HUT of CFS subjects caused a significant increase in nRT (148.0 ± 9.3 vs. 96.4 ± 6.0 ms at n = 4) compared with supine. Phenylephrine significantly reduced the HUT-induced increase in nRT in CFS to levels similar to supine (114.6 ± 7.1 vs. 114.6 ± 9.3 ms at n = 4). Compared with control subjects, CFS subjects are more sensitive both to orthostatic challenge and to baroreflex/chemoreflex-mediated interventions. Increasing blood pressure with phenylephrine can alter CBFv. In CFS subjects, mitigation of the HUT-induced CBFv decrease with phenylephrine has a beneficial effect on n-back outcome.

Caught in the thickness of brain fog: exploring the cognitive symptoms of Chronic Fatigue Syndrome

Chronic Fatigue Syndrome (CFS) is defined as greater than 6 months of persistent fatigue that is experienced physically and cognitively. The cognitive symptoms are generally thought to be a mild cognitive impairment, but individuals with CFS subjectively describe them as "brain fog." The impairment is not fully understood and often is described as slow thinking, difficulty focusing, confusion, lack of concentration, forgetfulness, or a haziness in thought processes. Causes of "brain fog" and mild cognitive impairment have been investigated. Possible physiological correlates may be due to the effects of chronic orthostatic intolerance (OI) in the form of the Postural Tachycardia Syndrome (POTS) and decreases in cerebral blood flow (CBF). In addition, fMRI studies suggest that individuals with CFS may require increased cortical and subcortical brain activation to complete difficult mental tasks. Furthermore, neurocognitive testing in CFS has demonstrated deficits in speed and efficiency of information processing, attention, concentration, and working memory. The cognitive impairments are then perceived as an exaggerated mental fatigue. As a whole, this is experienced by those with CFS as "brain fog" and may be viewed as the interaction of physiological, cognitive, and perceptual factors. Thus, the cognitive symptoms of CFS may be due to altered CBF activation and regulation that are exacerbated by a stressor, such as orthostasis or a difficult mental task, resulting in the decreased ability to readily process information, which is then perceived as fatiguing and experienced as "brain fog." Future research looks to further explore these interactions, how they produce cognitive impairments, and explain the perception of "brain fog" from a mechanistic standpoint.

Increasing orthostatic stress impairs neurocognitive functioning in chronic fatigue syndrome with postural tachycardia syndrome

CFS (chronic fatigue syndrome) is commonly co-morbid with POTS (postural tachycardia syndrome). Individuals with CFS/POTS experience unrelenting fatigue, tachycardia during orthostatic stress and ill-defined neurocognitive impairment, often described as 'mental fog'. We hypothesized that orthostatic stress causes neurocognitive impairment in CFS/POTS related to decreased CBFV (cerebral blood flow velocity). A total of 16 CFS/POTS and 20 control subjects underwent graded tilt table testing (at 0, 15, 30, 45, 60 and 75°) with continuous cardiovascular, cerebrovascular, and respiratory monitoring and neurocognitive testing using an n-back task at each angle. The n-back task tests working memory, concentration, attention and information processing. The n-back task imposes increasing cognitive challenge with escalating (0-, 1-, 2-, 3- and 4-back) difficulty levels. Subject dropout due to orthostatic presyncope at each angle was similar between groups. There were no n-back accuracy or RT (reaction time) differences between groups while supine. CFS/POTS subjects responded less correctly during the n-back task test and had greater nRT (normalized RT) at 45, 60 and 75°. Furthermore, at 75° CFS/POTS subjects responded less correctly and had greater nRT than controls during the 2-, 3- and 4-back tests. Changes in CBFV were not different between the groups and were not associated with n-back task test scores. Thus we conclude that increasing orthostatic stress combined with a cognitive challenge impairs the neurocognitive abilities of working memory, accuracy and information processing in CFS/POTS, but that this is not related to changes in CBFV. Individuals with CFS/POTS should be aware that orthostatic stress may impair their neurocognitive abilities.

Couples' perceptions of wives' CFS symptoms, symptom change, and impact on the marital relationship

The purpose of this descriptive correlational study was to describe the differences in couples' perceptions of wives' Chronic Fatigue Syndrome (CFS) symptoms and to describe the relationship between changing symptoms and the marital relationship. The convenience sample of 131 wives with CFS and their spouses reported symptom changes similarly. However, wives reported significantly higher problem levels for constitutional, fatigue, cognition, central nervous system (CNS), musculoskeletal, and allergy symptom domains and significantly less problem levels of mood disturbance domain than their husbands. Husbands who reported more symptom changes also reported lower marital adjustment, less empathy and support from their wives, and more conflict within the relationship. Wives who reported more symptom changes reported lower marital adjustment, less empathy for their husbands, and more conflict within the relationship and had husbands who reported lower marital adjustment and less empathy and support by the wives.