Clouding of consciousness

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Clouding of consciousness, also called brain fog or mental fog,

subjective sensation as their mind being "foggy".[4]

Background

The term clouding of consciousness has always denoted the main

DSM-IV replaced "clouding of consciousness" with "disturbance of consciousness" to make it easier to operationalize, but it is still fundamentally the same thing.[8] Clouding of consciousness may be less severe than delirium on a spectrum of abnormal consciousness.[3][9][10] Clouding of consciousness may be synonymous with subsyndromal delirium.[11]

Subsyndromal delirium differs from normal delirium by being overall less severe, lacking acuteness in onset and duration, having a relatively stable sleep-wake cycle, and having relatively stable motor alterations.[12] Subsyndromal delirium's significant clinical features are inattention, thought process abnormalities, comprehension abnormalities, and language abnormalities.[12] Delirium's full clinical manifestations may never be reached.[11] Among intensive care unit patients, subsyndromal subjects were as likely to survive as patients with a Delirium Screening Checklist score of 0, but required extended care at rates greater than 0-scoring patients (although lower rates than those with full delirium)[11] or have a decreased post-discharge level of functional independence vs. the general population but still more independence than full delirium.[12]

In clinical practice, no standard test is exclusive and specific; therefore, the diagnosis depends on the physician's subjective impression. The DSM-IV-TR instructs clinicians to code subsyndromal delirium presentations under the miscellaneous category "cognitive disorder not otherwise specified".[13]

Psychopathology

The conceptual model of clouding of consciousness is that of a part of the brain regulating the "overall level" of consciousness, which is responsible for awareness of oneself and of the environment.[3][14] Various etiologies disturb this regulating part of the brain, which in turn disturbs the "overall level" of consciousness.[15] This system of a sort of general activation of consciousness is called "arousal" or "wakefulness".[14]

It is not necessarily accompanied by

drowsiness.[16] Patients may be awake (not sleepy) yet still have a clouded consciousness (disorder of wakefulness).[17] Paradoxically, affected individuals say that they are "awake but, in another way, not".[18] Lipowski points out that decreased "wakefulness" as used here is not exactly synonymous with drowsiness. One is a stage on the way to coma, the other on the way to sleep, which is very different.[19][20]

The affected person has a sensation of mental clouding described in the patient's own words as "

cottonwood) on a cross-country road trip. She described feeling "out of it" and being in a "dreamy state". She described a sense of not trusting her own judgment and a dulled awareness, not knowing how much time had passed.[1] Clouding of consciousness is not the same thing as depersonalization, though people affected by both compare their experience to that of a dream. Psychometric tests produce little evidence of a relationship between clouding of consciousness and depersonalization.[23]

Brain fog may affect performance on virtually any cognitive task.[1] As one author put it, "It should be apparent that cognition is not possible without a reasonable degree of arousal."[3] Cognition includes perception, memory, learning, executive functions, language, constructive abilities, voluntary motor control, attention, and mental speed. Brain fog's most significant clinical features are inattention, thought process abnormalities, comprehension abnormalities, and language abnormalities.[12] The extent of the impairment is variable because inattention may impair several cognitive functions. Affected people may complain of forgetfulness, being "confused",[24] or being "unable to think straight".[24] Despite the similarities, subsyndromal delirium is not the same thing as mild cognitive impairment; the fundamental difference is that mild cognitive impairment is a dementia-like impairment, which does not involve a disturbance in arousal (wakefulness).[25]

In diseases

The term "brain fog" is used to represent a subjective condition of perceived cognitive impairment. It is defined as "a phenomenon of fluctuating states of perceived cognitive dysfunction that could have implications in the functional application of cognitive skills in people's participation in daily activities".[26] Brain fog is a common symptom in many illnesses where chronic pain is a major component.[26] Brain fog affects 15% to 40% of those with chronic pain as their major illness.[27] In such illnesses, pain processing may use up resources, decreasing the brain's ability to think effectively.[26]

Many people with

ADHD (attention deficit hyperactivity disorder), and studies have linked the two conditions, to the point that a fibromyalgia diagnosis has been proposed as an indication to screen for ADHD.[35][36][37] It is alternatively hypothesized that the increased pain compromises attention systems, resulting in cognitive problems.[34]

In

chronic fatigue syndrome, also known as myalgic encephalomyelitis, the CDC's recommended criteria for diagnosis[38] include that one of the following symptoms must be present:[38]

Lyme disease's neurologic syndrome, called Lyme encephalopathy, is associated with subtle memory and cognitive difficulties, among other issues.[39] Lyme can cause a chronic encephalomyelitis that resembles multiple sclerosis. It may be progressive and can involve cognitive impairment, migraines, balance problems, and other symptoms.[citation needed]

The emerging concept of

sluggish cognitive tempo has also been implicated in the expression of brain fog symptoms.[40]

Patients recovering from COVID-19 report experiencing brain fog, which can reflect a wide variety of

Brain fog and other neurological symptoms may also result from mold exposure.[42][43][44][45][46] This may be due to mycotoxin exposure and consequent innate immune system activation and inflammation, including in the central nervous system.[47][42][43][44][45][46] But adverse neurological health effects of mold exposure are controversial due to inadequate research and data, and more research is needed in this area.[47][48][49][42][44][46]

See also

References