Encephalopathy

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Etiology

Encephalopathy literally means disease of the brain. there are many etiologies for encephalopathy. For example, anoxic encephalopathy commonly refers to permanent brain damage with often severe impairment of consciousness and mental abilities caused by cessation of oxygen delivery to the brain. In contrast, toxic-metabolic encephalopathy, which has protean causes, is generally completely reversible given reversal of the underlying toxic (infectious) or metabolic insult. Because the word encephalopathy is used in so many contexts, it has no direct synonyms. Contrast to dementia which refers to a permanent reduction in mental abilities from a previously higher level (c.f. mental retardation), always in the absence of acute illness or alteration of consciousness. Also contrast to delirium which refers to an acute confusional state, frequently, but not always, in the setting of acute illness. Because toxic-metabolic encephalopathy is frequently a confusional state in the setting of illness, and delirium is a confusional state, often, but not always, in the setting of illness, the two intergrade seamlessly into each other.

A descriptive example may clarify the distinctions between these entities. An elderly person with Alzheimer's disease, manifested by mild dementia (forgetfulness and impaired judgment) develops pneumonia, a severe infection. They then manifest depressed consciousness, myclonic jerks, jactitation (restless tossing in bed, picking at things), and Cheyne-Stokes respirations (rhythmic increase and decrease in respiratory frequency and depth). These are symptoms (not exclusively) of toxic-metabolic encephalopathy. Because of the severity of their illness they are admitted to the intensive care unit, intubated with an endotracheal tube, mechanically ventilated, and sedated with medications. After a week their infection is cured and they are extubated and breathe independently. At this point they sleep during the day and are awake and agitated at night, have hallucinations, have alternating periods of lucidity and confusion, and manifest paranoia. This is delirium, arising from multiple previous insults (reduced baseline mental faculties, infection, psychoactive medications, altered environment, etc.). With cessation of psychoactive medications, enforcement of normal day/night dark/light cycles, and frequent, gentle, re-orientation to their surroundings, their confusion clears, leaving them mentally with their previous baseline dementia.

Types

There are many types of encephalopathy. Some examples include:

Causes

Encephalopathy alters brain function and/or structure. It may be caused by an infectious agent (bacteria, virus, or prion), metabolic or mitochondrial dysfunction, brain tumor or increased intracranial pressure, prolonged exposure to toxic elements (including solvents, drugs, alcohol, radiation, paints, industrial chemicals, and certain metals), chronic progressive trauma, poor nutrition, or lack of oxygen or blood flow to the brain. It is also known that concomitant use of lithium with other neuroleptics may, in rare cases, cause encephalopathy.

The hallmark of encephalopathy is an altered mental state. Depending on the type and severity of encephalopathy, common neurological symptoms are progressive loss of memory and cognitive ability, subtle personality changes, inability to concentrate, lethargy, and progressive loss of consciousness. Other neurological symptoms may include myoclonus (involuntary twitching of a muscle or group of muscles), nystagmus (rapid, involuntary eye movement), tremor, muscle atrophy and weakness, dementia, seizures, and loss of ability to swallow or speak.

Diagnosis

Blood tests, spinal fluid examination by lumbar puncture, imaging studies, electroencephalograms and similar diagnostic studies may be used to differentiate the various causes of encephalopathy.

Encephalopathy due to acute hepatic failure is vitally important to define because emergency liver transplantation and/or artificial liver support can save a life. The diagnosis is given by low level of factors of coagulability (V), intense jaundice and brain edema. Electroencephalogram can be useful. Encephalopathy due to chronic hepatic failure is also easy to recognize and is frequently triggered by protein intake or gastrointestinal bleeding.

Therapy

Treatment is symptomatic and varies, according to the type and severity of the encephalopathy. Anticonvulsants may be prescribed to reduce or halt any seizures. Changes to diet and nutritional supplements may help some patients. In severe cases, dialysis or organ replacement surgery may be needed.

Prognosis

Treating the underlying cause of the disorder may improve or reverse symptoms. However, in some cases, the encephalopathy may cause permanent structural changes and irreversible damage to the brain. Some encephalopathies can be fatal.

Reference

The Diagnosis of Stupor and Coma by Plum and Posner ISBN 0195138988 remains one the of best detailed observational references to the condition

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