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

Abstract

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.

Blunted cerebral blood flow velocity in response to a nitric oxide donor in postural tachycardia syndrome

“…In past work, using an executive memory task in younger POTS patients, we demonstrated that POTS patients exhibit a progressive cognitive impairment during step-wise incremental orthostatic stress (36). Moreover, cognitive impairment was associated with neurovascular uncoupling (35,52) such that the normal increase in CBF after neuronal activity (functional hyperemia) was absent in POTS patients (32,52). Neurovas- We have previously shown that POTS patients experience a deficit in NO-dependent vasodilation within the peripheral microcirculation, linked to oxidative stress (28,56).…”

“…One of the most debilitating symptoms of POTS is cognitive impairment (32,44), sometimes referred to as "brain fog" (43). In past work, using an executive memory task in younger POTS patients, we demonstrated that POTS patients exhibit a progressive cognitive impairment during step-wise incremental orthostatic stress (36).…”

Cns Findings in Chronic Fatigue Syndrome and a Neuropathological Case Report

“…Along with headache or vision problems, patients with CFS may experience cognitive and behavioral alterations. An excellent review by Ocon1 describes the ‘brain fog’ associated with CFS as slow thinking, difficulty focusing, lack of concentration, forgetfulness or haziness in thought processes. Clinically, reduced cerebral blood flow, increased activity in cortical/subcortical activation during mental tasks, deficits in processing information, impaired attention, and working memory are reported 1.…”

T. Egeland og medarbeidere svarer:

“…Billeddiagnostiske og nevropsykologiske tester viser avvikende funn i sentralnervesystemet hos pasienter med CFS/ME (37)(38)(39)(40)(41)(42)(43) . «Sentral sensitisering» (utvikling av hypersensitivitet for ulike stimuli i sentralnervesystemet), kan vaere en mekanisme ved CFS/ME (44)(45)(46) .…”