|Classification and external resources|
Encephalopathy /ɛnˌsɛfəˈlɒpəθi/ literally means disorder or disease of the brain. In modern usage, encephalopathy does not refer to a single disease, but rather to a syndrome of global brain dysfunction; this syndrome can be caused by many different illnesses.
In some contexts it refers to permanent (or degenerative) brain injury, and in others it is reversible. It can be due to direct injury to the brain, or illness remote from the brain. In medical jargon it can refer to a wide variety of brain disorders with very different etiologies, prognoses and implications. For example, prion diseases, all of which cause transmissible spongiform encephalopathies, are invariably fatal and have an infectious origin, but other encephalopathies are reversible and can be caused by nutritional deficiencies, toxins, and several other causes.
There are many types of encephalopathy. Some examples include:
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, exposure to toxins (including solvents, excess animal protein, drugs, alcohol, paints, industrial chemicals, and certain metals), radiation, trauma, poor nutrition, or lack of oxygen or blood flow to the brain.
The hallmark of encephalopathy is an altered mental state. Depending on the type and severity of encephalopathy, common neurological symptoms are loss of cognitive function, subtle personality changes, inability to concentrate, lethargy, and depressed consciousness. Other neurological signs may include myoclonus (involuntary twitching of a muscle or group of muscles), asterixis (abrupt loss of muscle tone, quickly restored), nystagmus (rapid, involuntary eye movement), tremor, seizures, jactitation (restless picking at things characteristic of severe infection), and respiratory abnormalities such as Cheyne-Stokes respiration (cyclic waxing and waning of tidal volume), apneustic respirations, and post-hypercapnic apnea.
Diagnosis is frequently clinical. That is, no set of tests give the diagnosis, but the entire presentation of the illness with nonspecific test results informs the experienced clinician of the diagnosis...
Treatment 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.
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.
The Diagnosis of Stupor and Coma by Plum and Posner ISBN 0195138988 remains one the of best detailed observational references to the condition