Encephalopathy ɛnˌsɛfəˈlɒpəθi means disorder or disease

Disease

A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...

 of the brain

Brain

The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

. In modern usage, encephalopathy does not refer to a single disease

Disease

A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...

, but rather to a syndrome

Syndrome

In medicine and psychology, a syndrome is the association of several clinically recognizable features, signs , symptoms , phenomena or characteristics that often occur together, so that the presence of one or more features alerts the physician to the possible presence of the others...

 of global brain dysfunction; this syndrome can be caused by many different illnesses.

Terminology

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 terms it can refer to a wide variety of brain disorders with very different etiologies, prognoses and implications. For example, prion

Prion

A prion is an infectious agent composed of protein in a misfolded form. This is in contrast to all other known infectious agents which must contain nucleic acids . The word prion, coined in 1982 by Stanley B. Prusiner, is a portmanteau derived from the words protein and infection...

 diseases, all of which cause transmissible spongiform encephalopathies

Transmissible spongiform encephalopathy

Transmissible spongiform encephalopathies , also known as prion diseases, are a group of progressive conditions that affect the brain and nervous system of many animals, including humans. According to the most widespread hypothesis they are transmitted by prions, though some other data suggest an...

, are invariably fatal, but other encephalopathies are reversible and can be caused by nutritional deficiencies, toxins, and several other causes.

Types

There are many types of encephalopathy. Some examples include:

• Mitochondrial encephalopathy
  MELAS
  Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes – abbreviated to MELAS – is one of the family of mitochondrial cytopathies, which also include MERRF, and Leber's hereditary optic neuropathy. It was first characterized under this name in 1984...
  
  —Metabolic disorder caused by dysfunction of mitochondrial DNA. Can affect many body systems, particularly the brain and nervous system.
• Glycine encephalopathy
  Glycine encephalopathy
  Glycine encephalopathy is a rare autosomal recessive disorder of glycine metabolism. After phenylketonuria, glycine encephalopathy is the second most common disorder of amino acid metabolism. The disease is caused by defects in the glycine cleavage system, an enzyme responsible for glycine...
  
  —A genetic metabolic disorder involving excess production of glycine
• Hepatic encephalopathy
  Hepatic encephalopathy
  Hepatic encephalopathy is the occurrence of confusion, altered level of consciousness and coma as a result of liver failure. In the advanced stages it is called hepatic coma or coma hepaticum...
  
  —Arising from advanced cirrhosis of the liver
• Hypoxic ischemic encephalopathy
  Cerebral hypoxia
  Cerebral hypoxia refers to a reduced supply of oxygen to the brain. Cerebral anoxia refers to a complete lack of oxygen to the brain. There are four separate categories of cerebral hypoxia; in order of severity they are; diffuse cerebral hypoxia , focal cerebral ischemia, cerebral infarction, and...
  
  —Permanent or transitory encephalopathy arising from severely reduced oxygen delivery to the brain
• Static encephalopathy—Unchanging, or permanent, brain damage
• Uremic encephalopathy—Arising from high levels of toxins normally cleared by the kidneys—rare where dialysis is readily available
• Wernicke's encephalopathy
  Wernicke's encephalopathy
  Wernicke encephalopathy is a syndrome characterised by ataxia, ophthalmoplegia, confusion, and impairment of short-term memory.It is caused by lesions in the medial thalamic nuclei, mammillary bodies, periaqueductal and periventricular brainstem nuclei, and superior cerebellar vermis, often...
  
  —Arising from thiamine deficiency, usually in the setting of alcoholism
• Hashimoto's encephalopathy
  Hashimoto's encephalopathy
  Hashimoto's Encephalopathy is a very rare condition associated with Hashimoto's thyroiditis. It was first described in 1966. It is classified as a neuroendocrine disorder....
  
  —Arising from an auto-immune disorder
• Hypertensive encephalopathy
  Hypertensive encephalopathy
  Hypertensive encephalopathy is a neurological dysfunction induced by malignant hypertension. The term "hypertensive encephalopathy" was introduced to describe this type of encephalopathy by Oppenheimer and Fishberg in 1928. It describes cerebral conditions, typically reversible, caused by sudden...
  
  —Arising from acutely increased blood pressure
• Lyme encephalopathy—Arising from the Borrelia burgdorferi
  Borrelia burgdorferi
  Borrelia burgdorferi is a species of Gram negative bacteria of the spirochete class of the genus Borrelia. B. burgdorferi is predominant in North America, but also exists in Europe, and is the agent of Lyme disease....
  
  bacteria.
• Toxic encephalopathy
  Toxic encephalopathy
  * Baker, E. . Chronic toxic encephalopathy caused by occupational solvent exposure. Annals of Neurology. 63: 545-547- External links :*****...
  
  —A form of encephalopathy caused by chemicals, often resulting in permanent brain damage
• Toxic-Metabolic encephalopathy—A catch-all for brain dysfunction caused by infection, organ failure, or intoxication
• Transmissible spongiform encephalopathy
  Transmissible spongiform encephalopathy
  Transmissible spongiform encephalopathies , also known as prion diseases, are a group of progressive conditions that affect the brain and nervous system of many animals, including humans. According to the most widespread hypothesis they are transmitted by prions, though some other data suggest an...
  
  —A collection of diseases all caused by prions, and characterized by "spongy" brain tissue (riddled with holes), impaired locomotion or coordination, and a 40 out of 40 fatality rate. Includes bovine spongiform encephalopathy
  Bovine spongiform encephalopathy
  Bovine spongiform encephalopathy , commonly known as mad-cow disease, is a fatal neurodegenerative disease in cattle that causes a spongy degeneration in the brain and spinal cord. BSE has a long incubation period, about 30 months to 8 years, usually affecting adult cattle at a peak age onset of...
  
   (mad cow disease), scrapie
  Scrapie
  Scrapie is a fatal, degenerative disease that affects the nervous systems of sheep and goats. It is one of several transmissible spongiform encephalopathies , which are related to bovine spongiform encephalopathy and chronic wasting disease of deer. Like other spongiform encephalopathies, scrapie...
  
  , and kuru
  Kuru (disease)
  Kuru is an incurable degenerative neurological disorder that is a type of transmissible spongiform encephalopathy, caused by a prion found in humans...
  
   among others.
• Neonatal encephalopathy—an obstetric form, often occurring due to lack of oxygen in bloodflow to brain-tissue of the fetus during labour or delivery
• Encephalomyopathy, a combination of encephalopathy and myopathy
  Myopathy
  In medicine, a myopathy is a muscular disease in which the muscle fibers do not function for any one of many reasons, resulting in muscular weakness. "Myopathy" simply means muscle disease...
  
  . Causes may include mitochondrial disease
  Mitochondrial disease
  Mitochondrial diseases are a group of disorders caused by dysfunctional mitochondria, the organelles that are the "powerhouses" of the cell. Mitochondria are found in every cell of the human body except red blood cells...
  
   (particularly MELAS
  MELAS
  Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes – abbreviated to MELAS – is one of the family of mitochondrial cytopathies, which also include MERRF, and Leber's hereditary optic neuropathy. It was first characterized under this name in 1984...
  
  ) or chronic hypophosphatemia
  Hypophosphatemia
  Hypophosphatemia is an electrolyte disturbance in which there is an abnormally low level of phosphate in the blood. The condition has many causes, but is most commonly seen when malnourished patients are given large amounts of carbohydrates, which creates a high phosphorus demand by cells,...
  
  , as may occur in cystinosis
  Cystinosis
  Cystinosis is a lysosomal storage disease characterized by the abnormal accumulation of the amino acid cystine. It is a genetic disorder that typically follows an autosomal recessive inheritance pattern. Cystinosis is the most common cause of Fanconi syndrome in the pediatric age group...
  
  .

Symptoms

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

Myoclonus

Myoclonus is brief, involuntary twitching of a muscle or a group of muscles. It describes a medical sign and, generally, is not a diagnosis of a disease. Brief twitches are perfectly normal. The myoclonic twitches are usually caused by sudden muscle contractions; they also can result from brief...

 (involuntary twitching of a muscle or group of muscles), asterixis

Asterixis

Asterixis is a tremor of the wrist when the wrist is extended , sometimes said to resemble a bird flapping its wings. This motor disorder is characterized by jerking movements and is associated with various encephalopathies due especially to faulty metabolism...

 (abrupt loss of muscle tone, quickly restored), nystagmus (rapid, involuntary eye movement), tremor, seizure

Seizure

An epileptic seizure, occasionally referred to as a fit, is defined as a transient symptom of "abnormal excessive or synchronous neuronal activity in the brain". The outward effect can be as dramatic as a wild thrashing movement or as mild as a brief loss of awareness...

s, 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

Blood test

Blood test

A blood test is a laboratory analysis performed on a blood sample that is usually extracted from a vein in the arm using a needle, or via fingerprick....

s, spinal fluid examination by lumbar puncture

Lumbar puncture

A lumbar puncture is a diagnostic and at times therapeutic procedure that is performed in order to collect a sample of cerebrospinal fluid for biochemical, microbiological, and cytological analysis, or very rarely as a treatment to relieve increased intracranial pressure.-Indications:The...

, imaging studies, electroencephalograms

Electroencephalography

Electroencephalography is the recording of electrical activity along the scalp. EEG measures voltage fluctuations resulting from ionic current flows within the neurons of the brain...

 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.

Therapy

Treatment varies according to the type and severity of the encephalopathy. Anticonvulsant

Anticonvulsant

The anticonvulsants are a diverse group of pharmaceuticals used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of bipolar disorder, since many seem to act as mood stabilizers, and in the treatment of neuropathic pain. The goal of an...

s 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.

Further reading

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