encephalopathy

Definition

Encephalopathy is a condition characterized by altered brain function and structure. It is caused by diffuse brain disease.

Description

Encephalopathy may be caused by advanced and severe disease states, infections, or as a result of taking certain medications. The three main causes of encephalopathy are liver disease, kidney disease, and lack of oxygen in the brain. The associated symptoms can include subtle personality changes, inability to concentrate, lethargy, progressive loss of memory and thinking abilities, progressive loss of consciousness, and abnormal involuntary movements. Symptoms vary with the severity and type of encephalopathy.

Encephalopathy may vary in severity from only subtle changes in mental state to a more advanced state that can lead to deep coma. Cerebral edema is a common manifestation of severe encephalopathy, which causes an increase in intracranial pressure. The major related causes of death include sepsis, circulatory collapse, and brain failure related to a syndrome encompassing cerebral edema, damaged blood-brain-barrier, increased intracranial pressure, brainstem herniation, and/or neurotoxins leaking into the brain and killing brain cells. Additionally, patients with severe encephalopathy usually develop intracranial hypertension, which can produce cerebral ischemia injury and cerebral herniation.

Demographics

There is no statistical information available for encephalopathy per se. Encephalopathy can occur at any age and there seems to be no gender or racial predilection, because encephalopathy is a manifestation of a primary illness.

Causes and symptoms

Causes

There is a wide variety of conditions that cause encephalopathy. Encephalopathy can be caused by infections (bacteria, viruses, or prions); lack of oxygen to the brain; liver failure; kidney failure; alcohol/drug overdose; prolonged exposure to toxic chemical (solvents, paints, industrial chemicals, drugs, radiation); metabolic diseases; brain tumor; increased intracranial pressure; and poor nutrition.

HYPOXIC ENCEPHALOPATHY Hypoxic encephalopathy refers to a lack of oxygen to the entire brain, which typically results in brain damage. Cerebral hypoxia can be caused by drowning, low blood pressure, birth injuries, cardiac arrest, strangulation, asphyxiation caused by smoke inhalation, severe hemorrhage, carbon monoxide poisoning, high altitudes, choking, tracheal compression, complications of anesthesia, paralysis of respiratory muscles, and respiratory failure.

Cardiac arrest is the most common condition that causes cerebral hypoxia. When the heart stops pumping, oxygen-rich blood cannot be delivered to vital organs such as the brain. Hypoxia to the brain causes irreversible brain damage after two minutes.

HEPATIC ENCEPHALOPATHY Hepatic encephalopathy refers to a condition of brain and nervous system damage caused by liver (hepatic) failure. Diseases that damage the liver causing impairment of the detoxification and functional capabilities of the liver can cause hepatic encephalopathy. Examples of disorders that decrease liver function are hepatitis or cirrhosis. Impairment in the detoxification capabilities of the liver causes accumulation of toxic chemicals in the blood such as ammonia, in addition to many other impurities that all collectively cause damage to the nervous system.

KIDNEY FAILURE The main function for the kidneys is to eliminate excess fluid and waste material from the blood. When the kidneys lose the ability to filter the blood, dangerous levels of waste products accumulate in the body. Chronic renal failure can be caused by diabetes, analgesic nephropathy (due to long-term use of aspirin or nonsteroidal anti-inflammatory drugs), kidney diseases (polycystic kidney disease, pyelonephritis, and glomerulonephritis), renal artery stenosis (a narrowing of the artery that supplies blood to the kidneys), and lead poisoning.

SEVERE INFECTIONS Severe infections, especially those that affect the brain, can cause encephalopathy. Infections that specifically target the brain are encephalitis, which is inflammation of the brain, typically caused by a virus, or meningitis, which is inflammation of the tissue that surrounds and protects the brain.

CHRONIC ALCOHOL USE Long-term use of alcohol not only causes destruction of brain cells but can cause cirrhosis of the liver or hepatitis, which results in the destruction of liver cells. Chronic alcoholism leads to progressive destruction of liver cells, which can cause end-stage liver failure. A subtype of hepatitis infection called hepatitis C typically causes progressive destruction to liver cells.

UREMIC ENCEPHALOPATHY Uremia describes the final stage of progressive renal insufficiency, which culminates in end-stage kidney failure with neurologic involvement. This is called uremic encephalopathy. The cause is unknown and no single metabolite or toxin is responsible for symptoms, but rather it is an accumulation of several chemicals/toxins in the blood that causes symptoms of encephalopathy.

Symptoms

The hallmark of encephalopathy is altered mental state. In mild cases, hypoxia can cause an altered mental state, which includes symptoms such as motor incoordination, poor judgment, and inattentiveness. Mild cases have no lasting effects. Patients who have severe hypoxia or anoxia (total lack of oxygen delivery, usually from cardiac arrest) lose consciousness within seconds. Other symptoms of encephalopathy include lethargy, nystagmus (rapid, involuntary eye movement), tremor, dementia, seizures, myoclonus (involuntary twitching of a muscle or group of muscles), muscle weakness and atrophy, and loss of ability to speak or swallow. An early and characteristic feature of hepatic encephalopathy is called constitutional apraxia, which is inability to reproduce simple designs such as a star. Patients with liver failure may exhibit a symptom called asterixis, an involuntary jerking tremor of the hands.

Diagnosis

The diagnosis of encephalopathy depends on the presence of acute or chronic liver disease; altered mental state such as confusion, stupor, or coma; symptoms of central nervous system damage; and abnormal wave patterns on an encephalogram. Diagnostic tests that may be utilized to establish the diagnosis include, but are not to limited to: complete blood count; liver function tests; ammonia and glucose levels; lactate levels (often elevated due to impaired tissue perfusion and because of decreased clearance by the liver); arterial blood gases (may reveal hypoxemia); kidney function tests; blood cultures (to detect infectious agents); virology testing (for hepatitis); neuroimaging studies; and ultrasound studies.

Treatment team

The causes of encephalopathies are broad. Additionally, the symptoms are also broad, ranging from mild changes of consciousness to coma or death. Therefore, the treatment team can consist of a broad spectrum of specialists that can include, but is not limited to, an internist, oncologist, pulmonologist, critical care physician, radiologist, hepatologist (specialist in liver diseases), and surgeon. The disorder can also occur in the pediatric ages or even at birth. In these critical situations, specialists in pediatric critical care, a neonatologist, and a perinatologist (specialist in maternal-fetal health) would be involved.

Treatment

Hypoxia or anoxic encephalopathy is an emergency, and immediate measures are necessary to prevent further damage to the brain and to restore breathing and circulation. It is necessary to treat hepatic encephalopathy early to prevent long-term damage. Specific treatment for hepatic encephalopathy is aimed at eliminating toxic substances and/or treatment of the primary illness that caused encephalopathy. Elimination of toxins such as ammonia can be accomplished by decreasing absorption of protein from the gut. By giving the patient a compound called lactulose, absorption of ammonia can be decreased. Persons with hepatic encephalopathy should not consume protein, and constipation should be avoided. Uremic encephalopathy caused by chronic renal failure is treated with transplantation or dialysis.

Recovery and rehabilitation

Recovery is an emergency for all patients with severe hypoxia or anoxia. Vital functions such as breathing, cardiac function, and delivery of oxygen-rich blood to the brain should be restored within two to five minutes. If anoxia persists for more than two minutes, there will be permanent and severe damage to the brain.

Clinical trials

There are four active government-sponsored clinical trials that are recruiting patients. There is a phase III clinical trial concerning birth asphyxia (hypoxic-ischemic encephalopathy) in infants up to six hours old. A phase II clinical trial is investigating the neuroimaging findings associated with persistent encephalopathy caused by the tick-transmitted infection called Lyme's disease (persistent Lyme encephalopathy). A third study is investigating a genetic form of familial dementia that causes encephaolpathy due to neurodegeneration of brain tissue. A fourth study investigates a disorder called neuronal ceroid lipofuscinosis (NCLS), which is a common heritable form of encephaopathy that occurs in one of 12,500 children. Detailed information about each of these studies can be obtained online from the website .

Prognosis

The outcome for patients who present with symptoms of encephalopathy depends on the cause. If the cause can be corrected in time, the outcome can be favorable. However, if encephalopathy is a manifestation of more advanced chronic disease, or if it is part of a rapidly fulminating disorder, the outcome can be poor and death may ensue due to the primary cause.

Special concerns

Persons who present with encephalopathy have advanced disease or the beginning of an advanced disease process. Vigilance on the part of the primary care provider is necessary to take all precautions to prevent this process.

Resources

BOOKS

Goetz, Christopher G., et al. (eds). Textbook of Clinical Neurology, 1st ed. Philadelphia: W.B. Saunders Company, 1999.

Goldman, Lee, et al. Cecil's Textbook of Medicine, 21st ed. Philadelphia: WB. Saunders Company, 2000.

Noble, John, et al. (eds). Textbook of Primary Care Medicine, 3rd ed. St. Louis: Mosby, Inc., 2001.

Rakel, Robert A. Textbook of Family Practice, 6th ed. Philadelphia: WB Saunders Company, 2002.

Rosen, Peter. Emergency Medicine: Concepts and Clinical Practice, 4th ed. St Louis: Mosby Year Book, Inc., 1998.

PERIODICALS

"Encephalopathy." eMedicine Series (July 2001).

Saas, David A. "Fulminant Hepatic Failure." Gastroenterology Clinics 32:4 (December 2003).

WEBSITES

NINDS Encephalopathy Information Page. National Institute of Neurological Disorders and Stroke. (May 20, 2004). http://www.ninds.nih.gov/health_and_medical/disorders/encephalopathy.htm.

ORGANIZATIONS

National Institute of Neurological Disorders and Stroke NIH Neurological Institute. P.O. Box 5801, Bethesda, MD 20824. (301) 496-5751 or (800) 352-9424. http://www.ninds.nih.gov.

Laith Farid Gulli, MD

Alfredo Mori, MB, BS

Any degenerative disease of the brain.

• biliary e., bilirubin e. — kernicterus.
• feline ischemic e. — an acute, ischemic cerebral necrosis causing various degrees of cerebral dysfunction including depression, ataxia, circling, behavioral changes, blindness and seizures.
• hepatic e. — severe hepatic insufficiency may induce a syndrome of excitability, tremor, compulsive walking, head pressing, and apparent blindness, followed by coma and convulsions, a dummy syndrome. The probable pathogenesis of this hepatic encephalopathy is the accumulation of ammonia, because of the failure of the liver to metabolize it, and the development of a spongy degeneration of the brain as a direct result of the hyperammonemia. A similar pathogenesis is hypothesized for the genesis of a cerebrotoxicant in companion animals with congenital defects in hepatic vasculature. See also portacaval shunt, hepatitis.
• hypernatremic e. — a severe hemorrhagic encephalopathy induced by the hyperosmolarity accompanying hypernatremia and dehydration.
• lead e. — brain disease caused by lead poisoning.
• e.–microphthalmia syndrome — an inherited disorder in hereford cattle with ocular and neurological defects and muscular dystrophy. Affected calves are blind and unable to stand.
• portosystemic e. — hepatic encephalopathy.
• transmissible mink e. — transmissible disease of mink which resembles scrapie in sheep. There is a very long incubation period, hyperirritability, biting, paralysis, coma and death. The scrapie agent is believed to be the cause.

This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (March 2008)

Encephalopathy /ɛnˌsɛfəˈlɒpəθi/ literally means disorder or disease of the brain. ^[1] 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.

Contents 1 Terminology 2 Types 3 Causes 4 Diagnosis 5 Therapy 6 Prognosis 7 References 8 See also

Terminology

In some contexts it refers to permanent (or degenerative)^[2] 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

Types

There are many types of encephalopathy. Some examples include:

• Mitochondrial encephalopathy - Metabolic disorder caused by dysfunction of mitochondrial DNA. Can affect many body systems, particularly the brain and nervous system.
• Glycine encephalopathy - A pediatric metabolic disorder
• Hepatic encephalopathy - Arising from advanced cirrhosis of the liver
• Hypoxic ischemic encephalopathy - 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 - Arising from thiamine deficiency, usually in the setting of alcoholism
• Hashimoto's encephalopathy - Arising from an auto-immune disorder
• Hypertensive encephalopathy - Arising from acutely increased blood pressure
• Lyme encephalopathy - Arising from the Borrelia Burgdorferi bacteria.
• Toxic encephalopathy - 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 - 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 (mad cow disease), scrapie, and kuru among others.

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, 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

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.

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. 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.

References

1. ^ "eMedicine/Stedman Medical Dictionary Lookup!". http://www.emedicine.com/asp/dictionary.asp?keyword=Encephalopathy. Retrieved 2008-11-30. 
2. ^ encephalopathy at Dorland's Medical Dictionary

• Adapted from http://www.ninds.nih.gov/disorders/encephalopathy/encephalopathy.htm

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

See also

• Brain damage
• Neurobiology
• Neurobiological brain disorder

v • d • e Pathology of the nervous system, primarily CNS (G00–G47, 320–349) Brain/ encephalopathy Inflammatory Encephalitis (Viral encephalitis, Herpesviral encephalitis) · Cavernous sinus thrombosis · Brain abscess (Amoebic) Degenerative Extrapyramidal and movement disorders Basal ganglia disease: Parkinsonism (Parkinson's disease, Postencephalitic parkinsonism)  · Neuroleptic malignant syndrome  · Pantothenate kinase-associated neurodegeneration · Progressive supranuclear palsy · Striatonigral degeneration · Hemiballismus · Huntington's disease · Olivopontocerebellar atrophy Dyskinesia: Dystonia (Spasmodic torticollis, Meige's, Blepharospasm) · Chorea (Choreoathetosis)  · Myoclonus (Myoclonic epilepsy) Essential tremor  · Restless legs  · Stiff person Dementia Alzheimer's (Early-onset)  · Frontotemporal dementia/Frontotemporal lobar degeneration (Pick's, Dementia with Lewy bodies) · Multi-infarct dementia Mitochondrial disease Leigh's Demyelinating autoimmune (Multiple sclerosis, Neuromyelitis optica, Schilder's disease) · hereditary (Adrenoleukodystrophy, Alexander, Canavan, Krabbe, ML, Pelizaeus-Merzbacher, VWM, MFC, CAMFAK syndrome) · Central pontine myelinolysis · Marchiafava-Bignami disease  · Alpers' Episodic/ paroxysmal Seizure/epilepsy Focal  · Generalised  · Status epilepticus  · Myoclonic epilepsy Headache Migraine (Familial hemiplegic)  · Cluster  · Vascular  · Tension Vascular Transient ischemic attack (Amaurosis fugax, Transient global amnesia) Cerebrovascular disease  · Stroke (MCA, ACA, PCA, Foville's, Millard-Gubler, Lateral medullary, Weber's, Lacunar stroke) Sleep disorders Insomnia  · Hypersomnia  · Sleep apnea (Obstructive, Ondine's curse)  · Narcolepsy  · Cataplexy  · Kleine-Levin  · Circadian rhythm sleep disorder (Advanced sleep phase syndrome, Delayed sleep phase syndrome, Non-24-hour sleep-wake syndrome, Jet lag) CSF Intracranial hypertension (Hydrocephalus/Normal pressure, Idiopathic intracranial hypertension) · Cerebral edema · Intracranial hypotension Other Brain herniation · Reye's  · Hepatic encephalopathy  · Toxic encephalopathy Spinal cord/ myelopathy Inflammatory Myelitis: Poliomyelitis · Demyelinating disease (Transverse myelitis) · Tropical spastic paraparesis Other Syringomyelia · Syringobulbia · Morvan's syndrome · Vascular myelopathy (Foix-Alajouanine syndrome) · Spinal cord compression Both/either Inflammatory Encephalomyelitis (Acute disseminated) Meningitis/Arachnoiditis: Bacterial (Tuberculous, Haemophilus, Pneumococcal) · Viral (Herpesviral) · Fungal (Cryptococcal) · Aseptic (Drug-induced) Meningoencephalitis Systemic atrophies SA Friedreich's ataxia · Ataxia telangiectasia MND UMN only: PLS · PP · HSP LMN only: PMA · PBP (Fazio-Londe, Infantile progressive bulbar palsy) · SMA (SMN-linked, Kennedy disease, SMAX2, DSMA1) both: ALS central nervous system navs: anat/physio/dev, noncongen/congen/neoplasia, symptoms+signs/eponymous, proc

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)