Grafman et al., 1993 DeLuca et al., 1995Ĭambridge neuropsychological test automated batteryĬaseras et al., 2006 Ocon et al., 2012 Stewart et al., 2012 Logical memory subtest of the Wechsler memory scale revised Wechsler adult intelligence scale revised Thus, to better understand cognitive impairment and “brain fog” in CFS, as well as to guide future research, the goal of this review is to summarize, standardize, and analyze the cognitive symptoms which lead to impairment. However, while much research has been done to analyze the individual components of the cognitive symptoms in CFS, no single source has compiled a comprehensive description of the multiple factors and their interactions that may play a role in the CFS patient's experience of “brain fog” (see Figure Figure1). Furthermore, functional magnetic resonance imaging (fMRI) of the brain has associated changes in anatomical structures to the cognitive fatigue experienced in CFS.
In addition, neurocognitive testing has localized the cognitive impairments in CFS to the domains of attention, information processing, memory, and reaction time (Cockshell and Mathias, 2010). Physiologically, areas of study have investigated mental fatigue and impairment as the effects of orthostatic stress, in relationship to changes in cerebral blood flow (CBF), and as a perception. Research has focused on describing “brain fog” and mild cognitive impairment in regards to CFS using objective measurements. Thus, “brain fog” may be conceptionally defined as the perception and experience of mental fatigue that is associated with and related to mild cognitive impairments in CFS. However, a precise definition of CFS “brain fog” has yet to be formulated. In fact, “brain fog” may be one of the most debilitating aspects of CFS (Jain and DeLisa, 1998 Natelson and Lange, 2002 Afari and Buchwald, 2003 Jorgensen, 2008).
These cognitive impairments have subjectively been described by patients with CFS as “brain fog.” Descriptions of “brain fog” include slow thinking, difficulty focusing, confusion, lack of concentration, forgetfulness, or a haziness in thought processes.
While the exact symptoms of each case of CFS are heterogeneous, up to 85% of individuals describe experiencing cognitive impairments (Komaroff, 1993). Additionally, at least four of the following symptoms must be concurrently present: pharyngeal pain, cervical or axillary lymphadenopathy, myalgia, polyarthritis without erythema or edema, headache, non-restful sleep, prolonged post-exercise fatigue, and/or debilitating cognitive impairments in short-term memory and concentration (Fukuda et al., 1994). The CDC requiring the fatigue to be of new onset, non-exertional, not improved with rest, and debilitating to a person's lifestyle (Fukuda et al., 1994). In 1994, the Center for Disease Control and Prevention (CDC) uniformly defined CFS. 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.Ĭhronic Fatigue Syndrome (CFS) is a clinically defined set of symptoms of unknown etiology most notable for persistent fatigue lasting greater than 6 months. 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.
The cognitive impairments are then perceived as an exaggerated mental fatigue. Furthermore, neurocognitive testing in CFS has demonstrated deficits in speed and efficiency of information processing, attention, concentration, and working memory. In addition, fMRI studies suggest that individuals with CFS may require increased cortical and subcortical brain activation to complete difficult mental tasks. 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). Causes of “brain fog” and mild cognitive impairment have been investigated. 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. Chronic Fatigue Syndrome (CFS) is defined as greater than 6 months of persistent fatigue that is experienced physically and cognitively.
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