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Encephalopathy (//; from Ancient Greek: ἐγκέφαλος "brain" + πάθος "suffering") means any disorder or disease of the brain, especially chronic degenerative conditions. In modern usage, encephalopathy does not refer to a single disease, but rather to a syndrome of overall brain dysfunction; this syndrome can have many different organic and inorganic causes.
Encephalopathy is a difficult term because it can be used to denote either a disease or finding (i.e., an observable sign in a patient).
When referring to a finding, encephalopathy refers to permanent (or degenerative) brain injury, or a reversible one. It can be due to direct injury to the brain, or illness remote from the brain. The individual findings that cause a clinician to refer to a patient as having encephalopathy include intellectual disability, irritability, agitation, delirium, confusion, somnolence, stupor, coma and psychosis. As such, describing a patient as having a clinical picture of encephalopathy is not a very specific description.
When referring to a disease, encephalopathy refers 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, but other encephalopathies are reversible and can have a number of causes including nutritional deficiencies and toxins.
The hallmark of encephalopathy is an altered mental state. Characteristic of the altered mental state is impairment of the cognition, attention, orientation, sleep–wake cycle and consciousness. An altered state of consciousness may range from failure of selective attention to drowsiness. Hypervigilance may be present; with or without: cognitive deficits, headache, epileptic seizures, myoclonus (involuntary twitching of a muscle or group of muscles) or asterixis ("flapping tremor" of the hand when wrist is extended).
Depending on the type and severity of encephalopathy, common neurological symptoms are loss of cognitive function, subtle personality changes, inability to concentrate. Other neurological signs may include dysarthria, hypomimia, problems with movements (they can be clumsy or slow), ataxia, tremor. Another neurological signs may include involuntary grasping and sucking motions, nystagmus (rapid, involuntary eye movement), 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. Focal neurological deficits are less common.
Wernicke's encephalopathy (alcoholic encephalopathy) can co-occur with Korsakoff's syndrome, characterized by amnestic-confabulatory syndrome: retrograde amnesia, anterograde amnesia, confabulations (invented memories), poor recall and disorientation.
Anti-NMDA receptor encephalitis is the most common autoimmune encephalitis. It can cause paranoid and grandiose delusions, agitation, hallucinations (visual and auditory), bizarre behavior, fear, short-term memory loss, and confusion.
There are many types of encephalopathy. Some examples include:
Chemotherapy medication, for example, fludarabine can cause a permanent severe global encephalopathy. Ifosfamide can cause a severe encephalopathy (but it can be reversible with stop using the drug and the use of methylene blue). Bevacizumab and other anti–vascular endothelial growth factor medication can cause posterior reversible encephalopathy syndrome.
Blood tests, cerebrospinal fluid examination by lumbar puncture (also known as spinal tap), brain imaging studies, electroencephalography (EEG), and similar diagnostic studies may be used to differentiate the various causes of encephalopathy.
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. These permanent deficits can be considered a form of stable dementia. Some encephalopathies can be fatal.