Clouding of consciousness

Clouding of consciousness, also known as brain fog or mental fog, is a term used in 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".

The term clouding of consciousness has always denoted the main pathogenetic feature of delirium since Greiner first pioneered the term (Verdunkelung des Bewusstseins) in 1817.The Diagnostic and Statistical Manual of Mental Disorders (DSM) has historically used the term in its definition of delirium. However, the DSM-III-R and the DSM-IV replaced “clouding of consciousness” with “disturbance of consciousness” to make it easier to operationalize, but it is still fundamentally the same thing. There now appears to be a trend among many doctors to 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. 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) or have a decreased post-discharge level of functional independence vs. the general population but still more independence than full delirium.

It is featured in such conditions as minimal hepatic encephalopathy (also known as subclinical hepatic encephalopathy or latent hepatic encephalopathy),subclinical Wernicke's encephalopathy, candidiasis,Lyme disease,anaphylaxis, intestinal tapeworms and lupus erythematosus. 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.

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