Clouding of consciousness, also known as brain fog or mental fog, is a term used
in conventional medicine denoting an abnormality in the regulation of the
overall level of consciousness that is mild and less severe than a delirium.
The sufferer experiences a subjective sensation of mental clouding described
as feeling "foggy". Background
The term clouding of consciousness has always denoted the main pathogenetic
feature of delirium since Greiner first pioneered the term in 1817. The
Diagnostic and Statistical Manual of Mental Disorders has historically used
the term in its definition of delirium. Recently the DSM has replaced “clouding”
with “disturbance” but it is still the same thing. Confusingly, however, there
appears to be a trend among many doctors to now redefine clouding of
consciousness to be less severe than delirium on a spectrum of abnormal
consciousness. In this case, it can be said that clouding of consciousness is
synonymous with subsyndromal delirium. 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. The significant clinical features of
subsyndromal delirium are inattention, thought process abnormalities,
comprehension abnormalities, and language abnormalities. The full
clinical manifestations of delirium may never be reached. Subsyndromal patients
are likely to survive but require institutionalization or have a decreased
post-discharge level of functional independence.
It is featured in such conditions as minimal hepatic encephalopathy,
subclinical Wernicke's encephalopathy, candidiasis, Lyme disease, anaphylaxis,
and intestinal tapeworms. The condition whereby intestinal faecal toxins bypass
the liver poisoning the brain causing clouding of consciousness used to be
referred to as "autointoxication" but is now referred to as "hepatic
encephalopathy". Minimal hepatic encephalopathy reduces quality of life
by impairing work activities, social interactions, and driving, but it does
not affect basic daily life activities such as dressing, personal hygiene,
eating, shopping, answering the phone, or taking public transportation.
Patients with MHE may even exhibit normal cognitive performances, but
overall productivity may suffer from inattentiveness and fatigue secondary to
attention abnormalities. Conventional doctors understudy and
neglect subsyndromal delirium because they "expect" delirium to be severe and
they prefer to dedicate their medical resources to managing the more immediate
"life-threatening" problems. They have a tendency to "psychologize" it and
misdiagnose it as depression or apathy. In fact, most clinicians believe that
minimal hepatic encephalopathy is "irrelevant" in spite of some evidence
indicating that the diagnosis may be important.
In clinical practice there is no standard test that is exclusive and
specific; therefore, the diagnosis depends on the subjective impression of
the physician. The DSM-IV-TR instructs clinicians to code subsyndromal delirium
presentations under the miscellaneous category of "cognitive disorder not
otherwise specified". Psychopathology
Neurologists conceptualize clouding of consciousness in terms of a part of the
brain regulating the "overall level" of the consciousness part of the brain,
which is responsible for awareness of oneself and of the environment. Various
etiologies disturb this regulating part of the brain, which in turn disturbs the
"overall level" of consciousness. This system of a sort of general activation
of consciousness is referred to as "arousal" or "wakefulness".
It is not necessarily accompanied by drowsiness, however. Patients may be
awake yet still have a clouded consciousness. Paradoxically, sufferers
declare that they are "awake but, in another way, not". 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. The sufferer experiences a subjective
sensation of mental clouding described in the patient's own words as feeling
"foggy". One sufferer described it as "I thought it became like misty, in some
way... the outlines were sort of fuzzy". Others may describe a "spaced out"
feeling. Sufferers compare their overall experience to that of a dream because as
in a dream consciousness, attention, orientation to time and place,
perceptions, and awareness are disturbed. Barbara Schildkrout, MD, a
board-certified psychiatrist and clinical instructor in psychiatry at the
Harvard Medical School described her subjective experience of clouding of
consciousness, or what she also called "mental fog", after taking a single dose
of the antihistamine chlorpheniramine for her cottonwood allergy while 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 long time went by. Clouding of consciousness
is not the same thing as depersonalization even though both
sufferers compare their experience to that of a dream. Psychometric tests
produce little evidence of a relationship between clouding of
consciousness and depersonalization. This may affect performance on virtually
any cognitive task. As one author put it, "It should be apparent that
cognition is not possible without a reasonable degree of arousal." Cognition
includes perception, memory, learning, executive functions, language,
constructive abilities, voluntary motor control, attention, and mental speed.
The most significant, however, are inattention, thought process
abnormalities, comprehension abnormalities, and language
abnormalities. The extent of the impairment is variable because
inattention may impair several cognitive functions. Sufferers may complain of
forgetfulness, being “confused”, or being “unable to think straight”.
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. Unscientific methods
Practitioners of non-evidence-based methods popularly use the term brain
fog. It is not always clear whether they mean mental fog, also known as clouding
of consciousness or perhaps something else like feelings of depersonalization
or mild cognitive impairment. Not to be confused, to expession Brain fag is also
a term popularly used these circles, but it is a culture-bound syndrome
characterized by complaints of the brain being "fatigued" and is not the same
thing as brain fog or mental fog. Chemotherapy
Chemotherapy can also cause "chemo brain" or "brain fog". See: PCCI -
Post-chemotherapy cognitive impairment See also
Altered level of consciousness Cognitive orthotics
Coma Delirium
Depersonalization disorder Excessive daytime sleepiness
Four boxes test Idiopathic hypersomnia
Insomnia Mental confusion
Mild cognitive impairment Obtundation
Pumphead syndrome Sleep inertia
Slow-wave sleep Sluggish cognitive tempo
Somnolence Stupor
References