Biofeedback

Biofeedback, a technique by which patients monitor their own bodily functions in an attempt to alter those functions. Primarily used in treating painful or stress-related conditions, biofeedback helps a patient control physiological processes that are normally considered involuntary.

In biofeedback training, electronic or mechanical instruments attached to the patient measure physical functioning, such as the degree of muscle tension. The machines then transform this information into amplified signals that the patient can hear or see—for example, a beep or a flashing light—thus enabling the patient to know when internal responses are abnormal. This feedback information (see Automation) can then guide the patient in trying to gain control over the internal condition.

Biofeedback learning has been likened to that involved in mastering an athletic skill. Although this kind of learning may occur in biofeedback, its benefits often are largely the result of relaxation induced by the procedure. Most treatments include training in formal relaxation techniques, which when used alone, often produce benefits equal to the biofeedback-assisted relaxation.

Biofeedback was developed in the late 1960s by scientists studying learning and the control of neuromuscular disorders, the autonomic nervous system, and mental states. Their work led to exaggerated claims that biofeedback would enable people to alter states of consciousness, lower blood pressure, and regulate heart functioning at will. Research has shown that although some degree of control is possible, it can be too limited to correct abnormal conditions.

Biofeedback is used to treat many disorders brought on or aggravated by stress, such as tension and migraine headaches, Raynaud's disease (abnormally cold hands and feet), tics, and muscle tension. It has shown particular promise in helping patients to recover the use of paralyzed limbs.

Fatigue

Fatigue (physiology), exhaustion of mind or body resulting from labor or exertion. Certain diseases, such as diabetes, cancer, and heart ailments, can also cause fatigue. Fatigue is characterized by the inability to perform physical tasks at one's usual pace or strength, and by a slowing of the thinking processes that may involve failure of memory.

The term fatigue is also used to denote a decreased susceptibility of a sensory receptor, such as the eye, to sensation. A red surface seems to become gray when it is stared at continuously, and the retina is said to be fatigued by long exposure to the color red. The same is true of hearing. A prolonged noise that is heard continuously becomes less intense due to fatigue of the processes of the inner ear. Continued mental exertion, as in a protracted working over of a problem, causes the condition known as mental fatigue.

Alzheimer’s Disease

Alzheimer’s Disease, progressive brain disorder that causes a gradual and irreversible decline in memory, language skills, perception of time and space, and, eventually, the ability to care for oneself. First described by German psychiatrist Alois Alzheimer in 1906, Alzheimer’s disease was initially thought to be a rare condition affecting only young people, and was referred to as presenile dementia.

Although Alzheimer’s disease is not a normal part of the aging process, the risk of developing the disease increases as people grow older. About 10 percent of the United States population over the age of 65 is affected by Alzheimer’s disease, and nearly 50 percent of those over age 85 may have the disease.

Alzheimer’s disease takes a devastating toll, not only on the patients, but also on those who love and care for them. Some patients experience immense fear and frustration as they struggle with once commonplace tasks and slowly lose their independence. Family, friends, and especially those who provide daily care suffer immeasurable pain and stress as they witness Alzheimer’s disease slowly take their loved one from them.

The causes of Alzheimer’s disease remain a mystery, but researchers have found that particular groups of people have risk factors that make them more likely to develop the disease than the general population. For example, people with a family history of Alzheimer’s are more likely to develop Alzheimer’s disease.

DIAGNOSIS

Alzheimer’s disease is only positively diagnosed by examining brain tissue under a microscope to see the hallmark plaques and tangles, and this is only possible after a patient dies. As a result, physicians rely on a series of other techniques to diagnose probable Alzheimer’s disease in living patients. Diagnosis begins by ruling out other problems that cause memory loss, such as stroke, depression, alcoholism, and the use of certain prescription drugs. The patient undergoes a thorough examination, including specialized brain scans, to eliminate other disorders. The patient may be given a detailed evaluation called a neuropsychological examination, which is designed to evaluate a patient’s ability to perform specific mental tasks. This helps the physician determine whether the patient is showing the characteristic symptoms of Alzheimer’s disease—progressively worsening memory problems, language difficulties, and trouble with spatial direction and time. The physician also asks about the patient’s family medical history to learn about any past serious illnesses, which may give a hint about the patient’s current symptoms.

TREATMENT

There is no known cure for Alzheimer’s disease, and treatment focuses on lessening symptoms and attempting to slow the course of the disease. Drugs that increase or improve the function of brain acetylcholine, the neurotransmitter that affects memory, have been approved by the United States Food and Drug Administration (FDA) for the treatment of Alzheimer’s disease. Called acetylcholinesterase inhibitors, these drugs have had modest but clearly positive effects on the symptoms of the disease. These drugs can benefit patients at all stages of illness, but they are particularly effective in the middle stage. This finding corresponds with new evidence that low acetylcholine levels in patients with Alzheimer’s disease may not be present in the earliest stage of the illness.

Senile Dementia

Senile Dementia, form of general intellectual impairment observed in elderly people. Approximately 10 percent of all people more than 65 years of age have clinically important intellectual impairment. Although about 20 percent of these cases may be due to treatable causes such as toxic drug reactions, most cases are what is known as Alzheimer's disease.

Senile dementia begins with failing attention and memory, loss of mathematical ability, irritability and loss of sense of humor, and poor orientation in space and time. Alzheimer's disease is relentlessly progressive and leads to death in 5 to 15 years. Examinations of the brains of persons who have died of Alzheimer's disease show characteristic twisted fibers, called neurofibrillary tangles, in certain areas of the brain, and cores of abnormal protein, called neuritic plaques, interspersed among nerve cells. No cure is known for Alzheimer's disease. A form of this disease strikes younger persons, in whom it is known as presenile dementia.

See also Aging; Geriatrics.

Brain Diseases and Disorders

Brain disorders have a wide range of causes, including head injury, stroke, bacterial diseases, complex chemical imbalances, and changes associated with aging.

Head Injury

Head injury can initiate a cascade of damaging events. After a blow to the head, a person may be stunned or may become unconscious for a moment. This injury, called a concussion, usually leaves no permanent damage. If the blow is more severe and hemorrhage (excessive bleeding) and swelling occur, however, severe headache, dizziness, paralysis, a convulsion, or temporary blindness may result, depending on the area of the brain affected. Damage to the cerebrum can also result in profound personality changes.

Damage to Broca's area in the frontal lobe causes difficulty in speaking and writing, a problem known as Broca's aphasia. Injury to Wernicke's area in the left temporal lobe results in an inability to comprehend spoken language, called Wernicke's aphasia.

An injury or disturbance to a part of the hypothalamus may cause a variety of different symptoms, such as loss of appetite with an extreme drop in body weight; increase in appetite leading to obesity; diabetes insipidus; hypothermia or fever; excessive emotionality; and uncontrolled anger or aggression. If the relationship between the hypothalamus and the pituitary gland is damaged (see Endocrine System), other vital bodily functions may be disturbed, such as sexual function, metabolism, and cardiovascular activity.

Stoke

A stroke is damage to the brain due to an interruption in blood flow. The interruption may be caused by a blood clot (see Embolism; Thrombosis), constriction of a blood vessel, or rupture of a vessel accompanied by bleeding. A pouchlike expansion of the wall of a blood vessel, called an aneurysm, may weaken and burst, for example, because of high blood pressure.

Brain Diseases

Epilepsy is a broad term for a variety of brain disorders characterized by seizures, or convulsions. Epilepsy can result from a direct injury to the brain at birth or from a metabolic disturbance in the brain at any time later in life.

Some brain diseases, such as multiple sclerosis and Parkinson disease, are progressive, becoming worse over time. Multiple sclerosis damages the myelin sheath around axons in the brain and spinal cord. As a result, the affected axons cannot transmit nerve impulses properly. Parkinson disease destroys the cells of the substantia nigra in the midbrain, resulting in a deficiency in the neurotransmitter dopamine that affects motor functions.

Cerebral palsy is a broad term for brain damage sustained close to birth that permanently affects motor function. The damage may take place either in the developing fetus, during birth, or just after birth and is the result of the faulty development or breaking down of motor pathways. Cerebral palsy is nonprogressive—that is, it does not worsen with time.

A bacterial infection in the cerebrum (see Encephalitis) or in the coverings of the brain (see Meningitis), swelling of the brain (see Edema), or an abnormal growth of healthy brain tissue (see Tumor) can all cause an increase in intracranial pressure and result in serious damage to the brain.

Scientists are finding that certain brain chemical imbalances are associated with mental disorders such as schizophrenia and depression. Such findings have changed scientific understanding of mental health and have resulted in new treatments that chemically correct these imbalances.

During childhood development, the brain is particularly susceptible to damage because of the rapid growth and reorganization of nerve connections. Problems that originate in the immature brain can appear as epilepsy or other brain-function problems in adulthood.

Several neurological problems are common in aging. Alzheimer's disease damages many areas of the brain, including the frontal, temporal, and parietal lobes. The brain tissue of people with Alzheimer's disease shows characteristic patterns of damaged neurons, known as plaques and tangles. Alzheimer's disease produces a progressive dementia (see Senile Dementia), characterized by symptoms such as failing attention and memory, loss of mathematical ability, irritability, and poor orientation in space and time.

Memory

Memory (psychology), processes by which people and other organisms encode, store, and retrieve information. Encoding refers to the initial perception and registration of information. Storage is the retention of encoded information over time. Retrieval refers to the processes involved in using stored information. Whenever people successfully recall a prior experience, they must have encoded, stored, and retrieved information about the experience. Conversely, memory failure—for example, forgetting an important fact—reflects a breakdown in one of these stages of memory.

TYPES OF MEMORY

Although the English language uses a single word for memory, there are actually many different kinds. Most theoretical models of memory distinguish three main systems or types: sensory memory, short-term or working memory, and long-term memory. Within each of these categories are further divisions.


Sensory Memory -> Sensory memory refers to the initial, momentary recording of information in our sensory systems. When sensations strike our eyes, they linger briefly in the visual system. This kind of sensory memory is called iconic memory and refers to the usually brief visual persistence of information as it is being interpreted by the visual system. Echoic memory is the name applied to the same phenomenon in the auditory domain: the brief mental echo that persists after information has been heard. Similar systems are assumed to exist for other sensory systems (touch, taste, and smell), although researchers have studied these senses less thoroughly.

Sensory memory systems typically function outside of awareness and store information for only a very short time. Iconic memory seems to last less than a second. Echoic memory probably lasts a bit longer; estimates range up to three or four seconds. Usually sensory information coming in next replaces the old information. For example, when we move our eyes, new visual input masks or erases the first image. The information in sensory memory vanishes unless it captures our attention and enters working memory.

Short-Term or Working Memory -> Psychologists originally used the term short-term memory to refer to the ability to hold information in mind over a brief period of time. As conceptions of short-term memory expanded to include more than just the brief storage of information, psychologists created new terminology. The term working memory is now commonly used to refer to a broader system that both stores information briefly and allows manipulation and use of the stored information.

We can keep information circulating in working memory by rehearsing it. For example, suppose you look up a telephone number in a directory. You can hold the number in memory almost indefinitely by saying it over and over to yourself. But if something distracts you for a moment, you may quickly lose it and have to look it up again. Forgetting can occur rapidly from working memory.

Long-Term Memory ->
The term long-term memory is somewhat of a catch-all phrase because it can refer to facts learned a few minutes ago, personal memories many decades old, or skills learned with practice. Generally, however, long-term memory describes a system in the brain that can store vast amounts of information on a relatively enduring basis. When you play soccer, remember what you had for lunch yesterday, recall your first birthday party, play a trivia game, or sing along to a favorite song, you draw on information and skills stored in long-term memory.

There seems to be no finite capacity to long-term memory. People can learn and retain new facts and skills throughout their lives. Although older adults may show a decline in certain capacities—for example, recalling recent events—they can still profit from experience even in old age. For example, vocabulary increases over the entire life span. The brain remains plastic and capable of new learning throughout one’s lifetime, at least under normal conditions. Certain neurological diseases, such as Alzheimer’s disease, can greatly diminish the capacity for new learning.

Amnesia

Amnesia, loss or impairment of memory. Amnesia is usually associated with some form of brain damage, but it may also be caused by severe psychological trauma. Amnesia with a physical cause is called organic amnesia, whereas amnesia of psychological origin is called functional amnesia.

Amnesia varies in its degree of severity. For example, a mild concussion may cause a person to forget recent events, but the memory loss may last only for several hours. On the other hand, severe head injuries may lead to permanent memory loss and an inability to learn new information. Amnesic individuals may retain normal cognitive abilities in other areas, such as language.

Anterograde amnesia is impairment in the ability to lay down new memories. It typically results from damage to the areas of the brain involved in long-term memory, including the hippocampus, the temporal lobes, and the frontal lobes. Such damage may result from brain infection (encephalitis), alcoholism, stroke, anoxia (severe oxygen deprivation), or head injury. An individual with severe anterograde amnesia might spend an entire day with a person and then, within a brief time, totally fail to recognize that person. Retrograde amnesia refers to difficulties in recalling or recognizing past events and experiences. It typically accompanies anterograde amnesia and is especially common following concussive head injury. A person with retrograde amnesia has trouble remembering recent events, events from further in the past, or both.

Amnesia is a symptom rather than a disease, and treatment attempts to determine and remove the basic cause. No treatments available will bring back the memory capacity of brain-damaged patients. However, these patients can be helped to make better use of their remaining memory skills. The most effective methods rely on memory aids, ranging from simple devices such as notebooks and timers to computer-based organizers and paging systems. Given such help, a severely amnesic person may be able to live independently.

See also Memory.

Concussion of the Brain

Concussion of the Brain, injury to the brain from a fall or a blow to the head, usually with loss of consciousness, the reason for which is not entirely understood. Increased pressure on the brain stem probably accounts for the slowing or temporary suspension of respiration and the reduced pulse rate that accompany a concussion; additional symptoms include pallor, sweating, and a drop in blood pressure. Dizziness, nausea, and a dull, restless feeling often follow a return to consciousness. Aftereffects such as headaches, dizziness, and nervousness may continue for several days, weeks, or even years after the initial injury. A concussion may temporarily or permanently damage nerve tissue, producing amnesia, irritability, and fatigue; memory is often impaired. Recovery from a concussion is generally complete and prompt after less severe injuries.

Headache

Headache, pain in any part of the head. Although the condition is widespread, less than 1 percent of all headaches indicate serious physical problems. This small percentage includes headaches caused by, or occurring after, concussion or injury to the head (see Concussion of the Brain), meningitis, encephalitis, stroke, or brain tumors. Headache may also accompany misalignment of the jaw or teeth. Short-lived headaches may occur after eating very cold foods or foods high in nitrites or monosodium glutamate. Caffeine withdrawal also may provoke headaches.

The majority of headaches belong to one of three main groups: migraine, a recurrent, severe headache, usually with throbbing on one side, accompanied by nausea and sometimes impaired vision; cluster, similar to migraine, but of short duration, occurring daily in series over weeks or months and predominantly in the area of one eye; and tension, a headache without consistent location thought to result from contractions of the face, scalp, or neck muscles.

Headaches are so common, and sometimes so difficult to alleviate, that several major clinics are devoted solely to their treatment. Most tension headaches respond to mild analgesics such as aspirin and acetaminophen. Severe migraine and cluster headaches do not respond to aspirin, but can be relieved by a variety of medications that affect the expansion or contraction of blood vessels. Headaches of all three major categories have been relieved in many cases with biofeedback techniques.

Migraine

Migraine, severe headache that occurs periodically and is sometimes confined to only one side of the head. A migraine is characterized by intense, throbbing, often blinding pain, and one or more of the following symptoms: sensitivity to light, nausea, vomiting, chills, facial swelling, tenderness of the scalp, sweating, frequent urination, irritability, visual hallucinations, and malaise. The headache may be preceded by a warning sensation, known as an aura, that may include flashes or patterns before the eyes, illusory tastes or odors, dizziness, tingling, or numbness.

At the onset of a migraine headache, blood vessels within the head constrict, causing a decrease in blood flow to the surface of the brain. Swelling of blood vessels in the head and scalp then sets off a chain of reactions that result in the headache. Among the biochemical changes associated with migraines are a reduced level of the neurotransmitter serotonin as well as an insufficient supply of enkephalins, the brain’s pain-relieving chemicals.

Hormonal level changes (such as those experienced by women during menopause or menstruation), endocrine imbalances, and stress due to anything from overwork to loud noises are considered precipitating factors of migraine headaches in susceptible people. Other factors that may trigger attacks include allergies, excess carbohydrates in the diet, foods rich in the trace element iodine, and alcoholic beverages.

Several treatments have been successful in helping migraine sufferers. These include medications such as sumatriptan and ergotamine tartrate, both of which shrink swollen blood vessels, thereby aborting the acute phase of a migraine attack; and propranolol, which stabilizes blood vessel tone and helps prevent subsequent attacks. Other drugs often prescribed to migraine sufferers are amitriptyline, phenelzine, and verapamil. Biofeedback techniques have also proven useful.

Epilepsy

Epilepsy, also called seizure disorder, chronic brain disorder that briefly interrupts the normal electrical activity of the brain to cause seizures, characterized by a variety of symptoms including uncontrolled movements of the body, disorientation or confusion, sudden fear, or loss of consciousness. Epilepsy may result from a head injury, stroke, brain tumor, lead poisoning, genetic conditions, or severe infections like meningitis or encephalitis.

DIAGNOSIS

In persons suffering from epilepsy, the brain waves, electrical activity in the part of the brain called the cerebral cortex, have a characteristically abnormal rhythm produced by excessive electrical discharges in the nerve cells. Because these wave patterns differ markedly according to their specific source, a recording of the brain waves, known as an electroencephalogram (EEG) is important in the diagnosis and study of the disorder (see electroencephalography). Diagnosis also requires a thorough medical history describing seizure characteristics and frequency.

IV TREATMENT

There is no cure for epilepsy but symptoms of the disorder may be treated with drugs, surgery, or a special diet. Drug therapy is the most common treatment—seizures can be prevented or their frequency lessened in 80 to 85 percent of cases by drugs known as anticonvulsants or antiepileptics. Surgery is used when drug treatments fail and the brain tissue causing the seizures is confined to one area and can safely be removed. A special high-fat diet known as a ketogenic diet produces a chemical condition in the body called ketosis that helps prevent seizures in young children. Like any medical condition, epilepsy is affected by general health. Regular exercise, plenty of rest, and efforts to reduce stress can all have a positive effect on a person with a seizure disorder.

Cerebral Palsy

Cerebral Palsy, a range of neuromuscular disorders caused by injury to an infant's brain sustained during late pregnancy, birth, or any time during the first two years of life. People with cerebral palsy have a wide range of difficulties, from a clumsy walk to an inability to speak or swallow, caused by faulty messages sent from the brain to the muscles. In the mid-1800s, William Little, an English physician, first described cerebral palsy in connection with birth injuries.

CAUSES

Advances in diagnostic technology have led to a much better understanding of the causes of cerebral palsy. Over half of the cases are now thought to be due to prenatal causes such as an infection that spreads from the mother to the fetus, maternal stroke that prevents proper blood supply to the fetus, exposure to environmental toxins, or problems in brain development.

The remaining cases are due to adverse events such as traumatic birth delivery, premature birth and its complications, meningitis (infection of the brain or its protective coverings), or head injury due to child abuse. Very rarely, heredity plays a role. In some cases, it is difficult to pinpoint a single event that may have caused cerebral palsy.

TREATMENT AND PREVENTION

Injury to the brain in individuals with cerebral palsy is permanent, and full recovery is not possible. Damaged brain tissue does not regenerate, but to some extent, normal nerve cells and nerve pathways can take over some function from injured areas, with some limitations. The degree of severity varies so greatly from case to case that it is difficult to make a general prognosis.

Successful treatment of cerebral palsy requires input from a variety of professionals. Physicians address health issues such as poor eyesight or restrictions in joint motion. Physical and occupational therapists help the child develop skills necessary to the activities of daily living. Speech pathologists deal with swallowing and speech dysfunction. Psychologists and educators work with emotional or learning difficulties. Nutritionists ensure normal growth. These professionals and numerous others work together as a team with the child or adult to help the individual achieve as much independence and competence as possible. In addition, family involvement in treatment, especially with children, is an essential component. With therapy, training, and community support, most individuals with cerebral palsy can lead meaningful and productive lives.

Many causes of cerebral palsy are preventable, especially those that occur at or after birth. Good prenatal care has been shown to minimize the likelihood of premature birth; new vaccines against Hemophilus influenzae have reduced the incidence of meningitis; and family support programs have reduced the number of cases of severe child abuse. Such preventive measures are cost-effective in that they reduce the expense of supporting individuals with cerebral palsy.

Disorders of the Nervous System

Consideration of disorders of the nervous system is the province of neurology; psychiatry deals with behavioral disturbances of a functional nature. The division between these two medical specialties cannot be sharply defined, because neurological disorders often manifest both organic and mental symptoms. For a discussion of functional mental illness, Mental Illness.

Diseases of the nervous system include genetic malformations, poisonings, metabolic defects, vascular disorders, inflammations, degeneration, and tumors, and they involve either nerve cells or their supporting elements. Vascular disorders, such as cerebral hemorrhage or other forms of stroke, are among the most common causes of paralysis and other neurologic complications. Some diseases exhibit peculiar geographic and age distribution. In temperate zones, multiple sclerosis is a common degenerative disease of the nervous system, but it is rare in the Tropics.

The nervous system is subject to infection by a great variety of bacteria, parasites, and viruses. For example, meningitis, or infection of the meninges investing the brain and spinal cord, can be caused by many different agents. On the other hand, one specific virus causes rabies. Some viruses causing neurological ills affect only certain parts of the nervous system. For example, the virus causing poliomyelitis commonly affects the spinal cord; viruses causing encephalitis attack the brain.

Inflammations of the nervous system are named according to the part affected. Myelitis is an inflammation of the spinal cord; neuritis is an inflammation of a nerve. It may be caused not only by infection but also by poisoning, alcoholism, or injury. Tumors originating in the nervous system usually are composed of meningeal tissue or neuroglia (supporting tissue) cells, depending on the specific part of the nervous system affected, but other types of tumor may metastasize to or invade the nervous system (see Cancer). In certain disorders of the nervous system, such as neuralgia, migraine, and epilepsy, no evidence may exist of organic damage. Another disorder, cerebral palsy, is associated with birth defects.

Treatment of Kidney Diseases and Disorders

Treatment of severe kidney disease may include kidney dialysis, a procedure in which blood is circulated through a machine that removes wastes and excess fluid from the bloodstream. Some patients use dialysis for a short time, while their kidneys recover from injury or disease. Others must use dialysis for their entire lives or until they undergo a kidney transplant. Kidney transplants are the most common of all transplant operations and have excellent success rates (see Medical Transplantation).

Kidney Dialysis

Kidney Dialysis, also known as hemodialysis, medical treatment used to remove waste materials from the blood of patients lacking renal function (see Kidney). Blood from an artery is pumped through a dialyzer, or artificial kidney, where it flows past a semipermeable membrane. Dialysis fluid passing on the other side of the membrane removes unwanted elements in the blood by diffusion. The blood is then returned to the body through a vein.

See also Treatment of Kidney Diseases and Disorders

Uremia

Uremia, presence in the bloodstream of too many chemical wastes such as urea, a nitrogen-rich waste product attributable to extra protein in the diet. As chemical wastes build up in the body they produce a toxic effect, possibly resulting in drowsiness, irritability, nausea, vomiting, breathlessness, headaches, and muscle cramps. In extreme cases, uremia may cause convulsions, coma, or death.

The kidneys normally filter chemical wastes from the blood and send them to the urinary system for elimination from the body.

Uremia most commonly develops when the kidneys fail to function properly. In some cases, however, uremia occurs when blood flow to the kidneys is reduced due to severe bleeding, serious burns, or heart attack, or when more wastes are formed in the bloodstream as a result of traumatic injuries or large surgical incisions than can be removed by the kidneys. A kidney stone, a tumor in the urinary tract, or a severely enlarged prostate in males may also cause uremia.

Victims of uremia due to kidney failure undergo kidney dialysis, a medical procedure that removes wastes from the blood. Transplantation of kidneys from healthy donors to uremic patients has also proven effective in some cases.

Encephalitis

Encephalitis, any infectious disease of the human central nervous system characterized by inflammation of the brain. The typical symptoms are headache, fever, and extreme lethargy, which lead eventually to coma; double vision, delirium, deafness, and facial palsy often occur in the acute stage of the disease. Aftereffects of encephalitis may include deafness, epilepsy, and dementia.

Several types of encephalitis are caused by viral infection of the central nervous system. These types fall into two main groups, primary neurotropic-virus infections (original virus infections in nerve tissues), and secondary infections occurring as complications of a primary virus infection elsewhere in the body.

NEUROTROPIC-VIRUS ENCEPHALITIS

This group comprises several epidemic diseases that primarily affect wild and domestic animals and birds. The disease is transmitted to humans from these animals by insect vectors. St. Louis encephalitis, first recognized in 1933 during an epidemic in St. Louis, Missouri, is transmitted to humans by mosquito bites. Other mosquito-borne types of encephalitis are Japanese B encephalitis, California encephalitis, and equine encephalomyelitis. Ticks are the insect vectors of Russian spring-summer encephalitis.

SECONDARY VIRUS INFECTIONS

This group includes two types, postinfective encephalitis and postvaccinal encephalitis. The first type occurs as an occasional complication of certain viral diseases, including mumps, measles, influenza, and yellow fever. Occasionally infections with the herpes virus involve the brain and cause brain damage or death. The second type may occur, although very infrequently, following the first vaccination with such attenuated-virus vaccines as those against smallpox and yellow fever (see Immune System).

OTHER TYPES

Encephalitis may occur as a result of an infection from a sporozoa called Toxoplasma, which is parasitic in animals, birds, and human beings. It can also be due to infection with the protozoan Trypanosoma cruzi, transmitted by the bite of the tsetse fly (see Trypanosomiasis). In addition, forms of apparently noninfectious encephalitis occur occasionally as a complication in cases of poisoning from contact with heavy metals, particularly lead (see Meningitis).

Meningitis

Meningitis, inflammation of the meninges, the membranes that surround the brain and spinal cord. Meningitis may be caused by a physical injury, a reaction to certain drugs, or more commonly, infection by certain viruses, bacteria, fungi, or parasites. This article focuses on meningitis caused by viral or bacterial infection.

The most common causes of viral meningitis are coxsackie viruses and echoviruses, although herpesviruses, the mumps virus, and many other viruses can also cause the disease. Viral meningitis is rarely fatal, and most patients recover from the disease completely.

Most cases of bacterial meningitis are caused by one of three species of bacteria—Haemophilus influenzae, Streptococcus pneumoniae, and Neisseria meningitidis. Many other bacteria, including Escherichia coli and the bacteria that are responsible for tuberculosis and syphilis, can also cause the disease. Bacterial meningitis can be fatal if not treated promptly. Some children who survive the infection are left with permanent neurological impairments, such as hearing loss or learning disabilities.

SYMPTOMS AND DIAGNOSIS

No matter what the cause, the symptoms of meningitis are always similar and usually develop rapidly, often over the course of a few hours. Nearly all patients with meningitis experience vomiting, high fever, and a stiff neck. Meningitis may also cause severe headache, back pain, muscle aches, sensitivity of the eyes to light, drowsiness, confusion, and even loss of consciousness. Some children have convulsions. In infants, the symptoms of meningitis are often more difficult to detect and may include irritability, lethargy, and loss of appetite. Most patients with meningococcal meningitis develop a rash of red, pinprick spots on the skin. The spots do not turn white when pressed, and they quickly grow to look like purple bruises.

Meningitis is diagnosed by a lumbar puncture, or spinal tap, in which a doctor inserts a needle into the lower back to obtain a sample of CSF. The fluid is then tested for the presence of bacteria and other cells, as well as certain chemical changes that are characteristic of meningitis.

TREATMENT AND PREVENTION

It is imperative to seek immediate medical attention if the symptoms of meningitis develop in order to determine whether the meningitis is viral or bacterial. Any delays in treating bacterial meningitis can lead to stroke, severe brain damage, and even death. Patients with bacterial meningitis are usually hospitalized and given large doses of intravenous antibiotics. The specific antibiotic used depends on the bacterium responsible for the infection. Antibiotic therapy is very effective, and if treatment begins in time, the risk of dying from bacterial meningitis today is less than 15 percent.

No specific treatment is available for viral meningitis. With bed rest, plenty of fluids, and medicine to reduce fever and control headache, most patients recover from viral meningitis within a week or two and suffer no lasting effects.

Good hygiene to prevent the spread of viruses is the only method of preventing viral meningitis. To help prevent the spread of bacterial meningitis, antibiotics are sometimes given to family members and other people who have had close contact with patients who develop the disease. Vaccines are also available against some of the bacteria that can cause meningitis. A vaccine against one strain of Haemophilus influenzae, once the most common cause of bacterial meningitis, was introduced during the 1980s and has been a part of routine childhood immunization.

Death and Dying

Death and Dying, the irreversible cessation of life and the imminent approach of death. Death involves a complete change in the status of a living entity—the loss of its essential characteristics.

PHYSIOLOGY

Death occurs at several levels. Somatic death is the death of the organism as a whole; it usually precedes the death of the individual organs, cells, and parts of cells. Somatic death is marked by cessation of heartbeat, respiration, movement, reflexes, and brain activity. The precise time of somatic death is sometimes difficult to determine, however, because the symptoms of such transient states as coma, faint (see Fainting), and trance closely resemble the signs of death.

After somatic death, several changes occur that are used to determine the time and circumstances of death. Algor mortis, the cooling of the body after death, is primarily influenced by the temperature of the immediate environment. Rigor mortis, the stiffening of the skeletal muscles, begins from five to ten hours after death and disappears after three or four days. Livor mortis, the reddish-blue discoloration that occurs on the underside of the body, results from the settling of the blood. Clotting of the blood begins shortly after death, as does autolysis, the death of the cells. Putrefaction, the decomposition that follows, is caused by the action of enzymes and bacteria.

Organs of the body die at different rates. Although brain cells may survive for no more than 5 minutes after somatic death, those of the heart can survive for about 15 minutes and those of the kidney for about 30 minutes. For this reason, organs can be removed from a recently dead body and transplanted into a living person.

Hemorrhagic Strokes

Hemorrhagic strokes account for the remaining 20 percent of all strokes. They occur when weakened blood vessels within the brain rupture and bleed into the surrounding tissue. The escaped blood can compress or pinch nearby blood vessels, cutting off blood flow and depriving the surrounding tissue of oxygen. Though hemorrhagic strokes occur less frequently than ischemic strokes, they tend to affect larger areas of the brain. Symptoms of a hemorrhagic stroke may be more sudden and more severe, and these strokes carry a greater risk of death than ischemic strokes.

Hemorrhagic strokes can result from an aneurysm, which develops when the wall of a blood vessel weakens and thins, ballooning outward. If left untreated, the aneurysm continues to expand and weaken, increasing the likelihood of rupture. Hemorrhagic strokes can also result from an arteriovenous malformation (AVM), a cluster of enlarged, structurally weak blood vessels that forms during fetal development or possibly at birth. These malformed blood vessels are susceptible to rupture from the normal forces exerted by the flowing blood.

Ischemic Strokes

Ischemic strokes, which account for about 80 percent of all strokes, are caused by an obstruction in an artery, generally one of the carotid arteries, the major arteries in the neck that carry oxygen-rich blood from the heart to the brain. The path to an ischemic stroke begins when atherosclerosis, in which fatty deposits build up on the inner wall of an artery, develops in one of the carotid arteries (see Arteriosclerosis). As the fatty deposit grows, it narrows the space through which blood can flow.

Atherosclerosis does not actually cause ischemic strokes, but it sets up the conditions that make them likely to occur. The actual obstruction that cuts off blood flow in an ischemic stroke is a blood clot. Often the obstruction develops by a process known as thrombosis, the formation of a clot inside a blood vessel. A clot is likely to form at the site of an atherosclerotic deposit because the deposit causes blood to flow in a turbulent, disorderly fashion. This turbulence can cause blood to clot just as it does in response to a wound. When the blood clot, or thrombus, develops at the site of an atherosclerotic deposit and cuts off blood flow to part of the brain, a stroke results.

An ischemic stroke can also be caused by a traveling clot, or embolus (see Embolism). In this case, the clot develops at some other location in the circulation, usually in one of the heart’s chambers. The clot then travels through the bloodstream until it encounters a vessel too small to let it pass through—often a vessel narrowed by atherosclerosis.

A transient ischemic attack (TIA) sometimes precedes an ischemic stroke. In a TIA, also known as a ministroke, strokelike symptoms develop but disappear within five minutes to 24 hours. TIAs can occur when a clot develops at the site of an atherosclerotic deposit but dissolves right away, or an embolism lodges in a narrowed vessel but is soon dislodged on its own. A TIA can also be caused by atherosclerosis alone when the narrowing of blood vessels by atherosclerosis restricts blood flow to part of the brain enough to cause strokelike symptoms. Regardless of the cause, the oxygen deprivation is not severe enough to kill brain cells, and the cells are able to bounce back from their injury. About 10 percent of ischemic strokes are preceded by TIAs.

Stroke

Stroke is a brain damage caused by a lack of blood flow to part of the brain. In order to perform its many functions and direct activities throughout the body—from walking to seeing to reasoning—the brain requires a constant supply of energy, provided by the oxygen and nutrients that are delivered by the flowing blood. If blood flow is restricted or cut off at any point between the heart and the brain, portions of the brain relying on blood from the obstructed blood vessel become deprived of oxygen. Brain cells are extremely sensitive to such oxygen deprivation, and if they are deprived of oxygen and nutrients for more than several minutes, they, in effect, starve to death. A stroke results in permanent damage to the brain tissue—and in many cases, permanent disability for the patient. For example, a patient who has had a stroke may develop paralysis on one or both sides of the body; have difficulty with walking, eating, or other daily activities; or lose the ability to speak or understand speech.

TYPES OF STROKE

Think of a blood vessel as a flexible, cylindrical tube, like a straw. The flow of liquid through a straw can be impeded in two different ways: by an obstruction within the straw, or by compression or pinching from outside the straw. The flow of blood through a blood vessel can also be blocked in these two ways. The two main types of stroke, ischemic stroke and hemorrhagic stroke, correspond to these two mechanisms of flow interruption.

SYMPTOM AND DIAGNOSIS

A key feature of stroke symptoms is that they are unexpected and develop suddenly, though they may worsen over the next several hours or days. The symptoms often primarily affect only one side of the body because blood flow is cut off to only part of the brain during a stroke. One of the most common symptoms is a sudden weakness or numbness of one side of the face or of one arm or leg. Some stroke sufferers experience a sudden dimness or loss of vision, particularly in only one eye. They may also suddenly become unable to speak or have trouble understanding speech. Sudden, severe headaches with no known cause and sudden, unexplained dizziness, unsteadiness, or falls, can also be warning signs of a stroke. Anyone who experiences one or more of these symptoms should seek medical attention immediately.

The key imaging technique used in diagnosing strokes is computed tomography (also known as CT or CAT scanning), which employs X rays to obtain images of the internal structures of the body. A CT scan can tell a doctor whether or not a stroke is occurring, whether the stroke is ischemic or hemorrhagic, and in most instances, the extent of brain damage caused by the stroke.

Several other imaging techniques are used along with computed tomography to gather more information about specific types of stroke. Magnetic resonance imaging (MRI) uses a magnetic field to generate images of the human body and produces high-resolution images that are particularly useful in diagnosing brain vessel abnormalities that may be involved in a hemorrhagic stroke. In X-ray angiography, a dye injected into the bloodstream is viewed using X rays to provide detailed images of blood vessels, enabling doctors to identify the source and location of an obstruction or gather anatomical information about aneurysms or AVMs. Two other imaging techniques, single photon emission computed tomography (SPECT) and positron emission tomography (PET), involve injecting a radioactive substance into the bloodstream. As the substance travels through the circulatory system, it constantly emits radiation, which is collected by a radiation detector. The images produced enable doctors to see regions of the brain with abnormally low blood flow, indicating brain tissue that has been injured or damaged by a stroke.

TREATMENT AND RECOVERY

Once doctors have established that a patient is having a stroke, the treatment focuses on removing the obstruction, restoring blood flow to the deprived region of the brain, and preventing the development of complications. In the past, doctors could do little to treat stroke patients until the stroke had run its course. However, a promising advance occurred in June 1996, when the Food and Drug Administration (FDA) approved the drug tissue plasminogen activator (t-PA) for use in treating ischemic strokes. The drug is a thrombolytic agent—or clot buster—that can break up blood clots and thereby restore flow through the obstructed blood vessel when administered within the first three hours of a stroke. This small window of effectiveness makes it more critical than ever for patients to seek immediate medical attention when strokelike symptoms develop.

Hypertension

Hypertension or High Blood Pressure, medical condition in which constricted arterial blood vessels increase the resistance to blood flow, causing an increase in blood pressure against vessel walls. The heart must work harder to pump blood through the narrowed arteries. If the condition persists, damage to the heart and blood vessels is likely, increasing the risk for stroke, heart attack, and kidney or heart failure. Often called the “silent killer,” hypertension usually causes no symptoms until it reaches a life-threatening stage.

Physicians use two measurements to describe blood pressure. Systolic pressure measures blood pressure as the heart contracts to pump out blood. Diastolic pressure measures blood pressure as the heart relaxes to allow blood to flow into the heart. An instrument called a sphygmomanometer measures systolic and diastolic pressure using units of millimeters of mercury (abbreviated mm Hg).

Blood pressure is classified in four categories: normal, prehypertension, stage 1 hypertension, and stage 2 hypertension. Normal blood pressure in an adult is less than 120/80 mm Hg, in which 120 describes systolic pressure and 80 describes diastolic pressure. Prehypertension is defined as a systolic pressure of 120 to 139 mm Hg or a diastolic pressure of 80 to 89 mm Hg. People with prehypertension are likely to develop hypertension at some point during their life. Stage 1 hypertension is defined as a systolic pressure of 140 to 159 mm Hg or a diastolic pressure of 90 to 99 mm Hg. Stage 2 hypertension is defined as 160/100 mm Hg or higher.

HOW HYPERTENSION DEVELOPS

Two factors determine blood pressure: the amount of blood the heart pumps and the diameter of the arteries receiving blood from the heart. When the arteries narrow, they increase the resistance to blood flow. The heart works harder to pump more blood to make sure the same amount of blood circulates to all the body tissues. The more blood the heart pumps and the smaller the arteries, the higher the blood pressure.

The kidneys play a major role in the regulation of blood pressure. Kidneys secrete the hormone renin, which causes arteries to contract, thereby raising blood pressure. The kidneys also control the fluid volume of blood, either by retaining salt or excreting salt into urine. When kidneys retain salt in the bloodstream, the salt attracts water, increasing the fluid volume of blood. As a higher volume of blood passes through arteries, it increases blood pressure.

Blood Pressure

Blood Pressure, pressure of circulating blood against the walls of the arteries (blood vessels that carry blood from the heart to the rest of the body). Blood pressure is an important indicator of the health of the circulatory system. Any condition that dilates or contracts the arteries or affects their elasticity, or any disease of the heart that interferes with its pumping power, affects blood pressure.

In a healthy human being, blood pressure remains within a certain average range. The complex nervous system mechanisms that balance and coordinate the activity of the heart and arterial muscles permit great local variation in the rate of blood flow without disturbing the general blood pressure.

Hemoglobin, the iron-protein compound that gives blood its red color, also plays a role in regulating local variation in blood pressure. Hemoglobin carries nitric oxide, a gas that relaxes the blood vessel walls. Hemoglobin controls the expansion and contraction of blood vessels, and thus blood pressure, by regulating the amount of nitric oxide to which the vessels are exposed.

Two measurements are used to describe blood pressure. Systolic pressure measures blood pressure when the heart contracts to empty its blood into the circulatory system. Diastolic pressure measures blood pressure when the heart relaxes and fills with blood. Systolic and diastolic pressure are measured in millimeters of mercury (abbreviated mm Hg) using an instrument called a sphygmomanometer. This instrument consists of an inflatable rubber cuff connected to a pressure-detecting device with a dial. The cuff is wrapped around the upper arm and inflated by squeezing a rubber bulb connected to it by a tube. Meanwhile, a health-care professional listens to a stethoscope applied to an artery in the lower arm. As the cuff inflates, it gradually compresses the artery. The point at which the cuff stops the circulation and at which no pulsations can be heard through the stethoscope is read as the systolic pressure. As the cuff is slowly deflated, a spurting sound can be heard when the heart contraction forces blood through the compressed artery. The cuff is then allowed gradually to deflate further until the blood is flowing smoothly again and no further spurting sound is heard. A reading at this point shows the diastolic pressure that occurs during relaxation of the heart. Normal blood pressure in an adult is less than 120/80 mm Hg. The first number describes systolic pressure, while the second number describes diastolic pressure.

Blood pressure is influenced by a wide range of factors and varies between individuals and in the same individual at different times. For instance, blood pressure naturally increases with age because the arteries lose the elasticity that, in younger people, absorbs the force of heart contractions. Other factors, such as emotions, exercise, or stress, may temporarily raise blood pressure.

Abnormally high blood pressure, known as hypertension, that remains untreated can lead to stroke, heart attack, and kidney or heart failure. Hypertension may have no known cause or it may result from heart or blood vessel disorders or from diseases affecting other parts of the body. Abnormally low blood pressure, known as hypotension, may be caused by shock, malnutrition, or some other disease or injury.

First Aid

First Aid, emergency care for a victim of sudden illness or injury until more skillful medical treatment is available. First aid may save a life or improve certain vital signs including pulse, temperature, a patent (unobstructed) airway, and breathing. In minor emergencies, first aid may prevent a victim’s condition from worsening and provide relief from pain. First aid must be administered as quickly as possible. In the case of the critically injured, a few minutes can make the difference between complete recovery and loss of life.

First-aid measures depend upon a victim’s needs and the provider’s level of knowledge and skill. Knowing what not to do in an emergency is as important as knowing what to do. Improperly moving a person with a neck injury, for example, can lead to permanent spinal injury and paralysis.

Despite the variety of injuries possible, several principles of first aid apply to all emergencies. The first step is to call for professional medical help. Determine that the scene of the accident is safe before attempting to provide first aid. The victim, if conscious, should be reassured that medical aid has been requested, and asked for permission to provide any first aid. Next, assess the scene, asking bystanders or the injured person’s family or friends about details of the injury or illness, any care that may have already been given, and preexisting conditions such as diabetes or heart trouble. The victim should be checked for a medical bracelet or card that describes special medical conditions. Unless the accident scene becomes unsafe or the victim may suffer further injury, do not move the victim.

First aid requires rapid assessment of victims to determine whether life-threatening conditions exist. One method for evaluating a victim’s condition is known by the acronym ABCs, which stands for:

A — Airway—is it open and unobstructed?

B — Breathing—is the person breathing? Look, listen, and feel for breathing.

C — Circulation—is there a pulse? Is the person bleeding externally? Check skin color and temperature for additional indications of circulation problems.

Once obvious injuries have been evaluated, the injured person’s head should be kept in a neutral position in line with the body. If no evidence exists to suggest potential skull or spinal injury, place the injured person in a comfortable position. Positioned on one side, a victim can vomit without choking or obstructing the airway.

Before treating specific injuries, protect the victim from shock—a depression of the body’s vital functions that, left untreated, can result in death. Shock occurs when blood pressure (pressure exerted against blood vessel walls) drops and the organs do not receive enough blood, depriving them of oxygen and nutrients. The symptoms of shock are anxiety or restlessness; pale, cool, clammy skin; a weak but rapid pulse; shallow breathing; bluish lips; and nausea. These symptoms may not be apparent immediately, as shock can develop several hours after an accident. To prevent shock, the victim should be covered with blankets or warm clothes to maintain a normal body temperature. The victim’s feet should be elevated. Because of the danger of abdominal injuries, nothing should be administered by mouth.

Artificial Respiration

Artificial Respiration, forcing of air into and out of the lungs of one person by another person or by mechanical means. It is usually employed during suspension of natural respiration caused by disease, such as poliomyelitis or cardiac failure; by electric shock; by an overdose of depressive drugs such as morphine, barbiturates, or alcohol; or by suffocation resulting from drowning, breathing noxious gases, or blockage of the respiratory tract. If the brain is deprived of oxygen for five minutes, it may be permanently damaged; slightly longer periods without oxygen usually result in death. The exception is drowning in very cold water, in which the body's oxygen demand is greatly reduced; people have been revived after being submerged for one-half hour in cold water.

In the mouth-to-mouth method the unconscious person is laid faceup with the head tilted as far back as possible to prevent the tongue from blocking the air passages. The victim's nose is then pinched shut, and with the reviver's mouth tightly covering the victim's, the reviver gives four quick, deep breaths. If breathing does not resume, the reviver proceeds to give one breath each five seconds, allowing the air to come out of the victim's lungs between breaths. This is continued until the victim resumes breathing or until trained help arrives. If the unconscious person is a baby or small child, both the mouth and nose are covered with the reviver's mouth, and small puffs of air are breathed out to the victim at the rate of one every three seconds.

To restore breathing to a person who is choking, a rescuer gives four quick blows between the victim's shoulder blades with the heel of the hand. If this does not dislodge the obstruction, the rescuer uses the stomach thrust, popularly called the Heimlich maneuver after its developer, the American physician Henry Jay Heimlich. The rescuer places the side of the fist against the victim's stomach, below the ribs and above the navel. Then, using the other hand, the rescuer thrusts the fist up into the victim's stomach forcefully four times. With children, a rescuer first turns the child head-down and slaps the child's back. In applying the Heimlich maneuver to children, the rescuer uses only the first hand, and not the second.

A type of respiratory first aid that requires special training is called cardiopulmonary resuscitation (CPR). In this procedure, which is used for a person who has had a heart attack, the reviver alternately breathes for the victim and performs external massage on the person's chest to keep blood moving through the body. This technique is more easily done by two trained people, one performing each maneuver. This technique is more easily done by two trained people, one performing each maneuver. If the procedure lasts for a long time, it is best that the two people switch positions to be able to sustain the procedure. See also First Aid.

Theophylline

Theophylline, prescription drug used to treat asthma, a chronic disease of the respiratory system. It is also used to treat asthmalike symptoms in patients with emphysema, chronic bronchitis, and pulmonary (lung) disease. Theophylline is sometimes used to treat breathing problems in infants at risk for sudden infant death syndrome (SIDS). As a bronchodilator, the drug works by relaxing constricted muscles of the lung’s bronchi, the two branches of the trachea (windpipe) that lead to the lungs. It also opens blood vessels in the lungs, improving circulation.

Theophylline is available in capsule, tablet, and liquid form. All are taken orally, usually with food to prevent stomach irritation. Dosage in children under the age of 16 is based on body weight. Adult dosages usually start at 200 mg taken twice a day, which may be increased if needed. The maximum adult dose is 900 mg per day. Effectiveness is usually apparent within 48 to 72 hours.

Patients with peptic ulcers, seizure disorders, impaired liver or kidney function, high blood pressure, irregular heartbeat, or heart disease should use this drug with caution. Theophylline should not be used by breast-feeding women and should be avoided during pregnancy.

Side effects may include nausea or restlessness, especially when starting treatment with theophylline. Other possible side effects are diarrhea, headache, increased urination, insomnia, low blood pressure, or skin rash. Changes in heart rate, another possible side effect, should be checked by a doctor. Symptoms of overdose can include the side effects described above or more severe effects including high fever, convulsions, or coma.

Theophylline may interact adversely with the medication in a flu shot. It also may interact with cimetidine, ciprofloxacin, clarithromycin, doxycycline, erythromycin, phenytoin, propanolol, and birth control pills.

Brand Names: Slo-bid, Theo-dur

Bronchodilator

Bronchodilator, any of a group of drugs that expand the air passages (bronchial tubes) of the lungs. Bronchodilators are used to treat asthma, bronchitis, emphysema, and other diseases that affect the lungs. They relieve symptoms such as wheezing, shortness of breath, and coughing, and restore the patient’s ability to breathe comfortably.

Bronchodilators work in various ways. Some, such as albuterol, affect the sympathetic nervous system, dilating the walls of the bronchial tubes. Others, such as theophylline, interfere with the action of certain enzymes or cells within the lungs, relaxing the constricted muscles of the airway.

Many bronchodilators are inhaled through the mouth, especially those that provide immediate relief from an asthma attack. Some are taken orally in tablet or liquid form while others are injected into the skin. Inhaled bronchodilators are often prescribed with a dosage of 1 or 2 inhalations up to 4 times per day. A typical tablet dosage is 2 to 4 mg taken 3 to 4 times per day. Some bronchodilators begin to work within minutes of a dose. Others are not designed for immediate relief of symptoms and may take several weeks to take effect.

Patients taking bronchodilators are usually cautioned to avoid using other drugs to treat their symptoms, especially inhaled medications, unless a doctor advises otherwise. The effect of bronchodilators on pregnant women has not been well-studied in humans, although some types of bronchodilators produce birth defects in animals when administered in high doses.

Medical Transplantation

Medical Transplantation, transfer of a living tissue or organ to an injured or ill person to restore health or reduce disability. Over the past 45 years, surgeons have made great strides in their ability to implant organs in people who are seriously ill. At least 21 different organs—such as hearts, livers, and kidneys—and tissues—such as corneas and bone marrow—can now be successfully transplanted into patients who can then expect to survive for years or even decades. Improved surgical techniques are partly responsible for the success of organ transplants, but a more important factor is the development of drugs that can suppress the body’s rejection of the implanted organ without also leaving the patient highly susceptible to infections.

Kidneys are the most common organs to be transplanted. Kidneys remove waste products from the blood stream. If they fail, often as a result of diabetes mellitus or cancer, a person can die from the buildup of these toxic materials. The waste products can be removed artificially through a process called kidney dialysis, but the patient must be hooked up to the dialysis machine two to three times each week for as long as 12 hours at a time. Kidney transplants free the recipient from dependence on dialysis. If the kidney is rejected, the patient must go back on dialysis or receive another transplant.

Heart transplants are perhaps the most dramatic of all organ transplants because without a functioning heart, a patient cannot survive more than a few minutes. The heart is also more sensitive to a lack of blood than other organs, and can be preserved for only a few hours without damage.

Liver failure caused by cirrhosis, cancer, or hepatitis can be fatal. The liver is the only internal organ with the capacity to regenerate. This capacity provides the surgeon additional flexibility in treating liver damage. For instance, if the damage is not very severe, a temporary transplant can take over the liver’s function while the patient’s own liver recovers. It is also possible to remove part of a liver from a living donor and transplant it. After the surgery both the donor’s liver and the transplanted portion will grow to full size.

Lung transplants are used to replace a single diseased lung, and sometimes both lungs. In some cases lung disease has damaged the heart, and these cases may benefit from a combined heart-lung transplantation. Successful lung transplants are hampered by the difficulty in preserving a lung from a person who has recently died so that it is still viable by the time a proper recipient is found.

The most common tissue transplant is blood transfusion, commonly used to replace blood lost by a person in an accident or during surgery. Other tissues commonly transplanted include bone marrow, corneas, skin, bone, cartilage, tendons, and blood vessels.

Hemophilia

Hemophilia, hereditary blood disease characterized by the inability of blood to clot, or coagulate, leading to hemorrhage, or excessive bleeding, even from minor injuries. The disease is caused by an insufficiency or absence of certain blood proteins, called factors, that participate in blood clotting. The most common form, hemophilia A, is observed in 80 percent of hemophiliacs and is caused by a lack of factor VIII; in the second most common, hemophilia B (Christmas disease), factor IX is missing. The severity of hemophilia varies greatly. The bleeding may occur as excessive bruising or persistent bleeding after a simple cut. Hemorrhaging into joints and muscles can be disabling. Before the advent of modern therapy, the chance of survival to adulthood was poor.

About 80 percent of all cases of hemophilia have an identifiable family history of the disease; in other instances, it may be attributable to a spontaneous mutation of genes. Researchers recently discovered that the spontaneous mutation of the factor VIII gene in two children was due to the attachment of a foreign “jumping gene” (see Genetics) that disrupted the blood-clotting ability of the factor VIII gene. Inheritance is controlled by a recessive sex-linked factor carried by the mother on the X chromosome. A probability of one in two exists that each boy born to a normal male and a carrier female will be hemophiliac and the same chance that each girl of this union will be a carrier. Of the children of a hemophiliac male and a normal female, all the girls will be carriers and all the boys will be normal. Males cannot transmit the disability, and female carriers are free of the disease.

Prevention of injury is important for the patient with hemophilia. When bleeding occurs, replacement therapy may be necessary. Freshly frozen blood plasma can be used to treat mild forms of the disease. In severe cases, hemophiliacs can administer plasma extracts at home either in a freeze-dried form that is storable for six months at room temperature or for a year in the refrigerator; or else in a form called cryoprecipitate, a concentrate that is prepared from fresh blood and must be refrigerated. Cryoprecipitate and other types of concentrates are less likely to transport diseases such as hepatitis and acquired immunodeficiency syndrome (AIDS) because concentrates are prepared from the blood of a single donor, whereas plasma comes from large pools obtained from many donors. Screening of donors and heat treatment of plasma products have recently decreased the risk of disease transmission. The cloning of factor VIII by genetic engineering allowed the development of a completely safe replacement product that was approved by the Food and Drug Administration (FDA) for commercial production in 1992. Unfortunately, a high percentage of hemophiliacs have already been exposed to the AIDS virus.

Anemia

Anemia (Greek for “bloodlessness”), a blood condition involving an abnormal reduction in the number of red blood cells (erythrocytes) or in their hemoglobin content. These cells are the means by which oxygen is carried to the various parts of the body. People who are anemic develop symptoms caused by the inadequate delivery of oxygen to their body tissues. There are three primary causes of anemia: (1) reduced production of red blood cells, which may result from deficiency in nutrients or hormones, or from disease or other conditions; (2) excessive destruction of red blood cells, often a hereditary problem; and (3) excessive blood loss.

The most common type of anemia is iron-deficiency anemia, which occurs when the body's need for iron increases, as during certain periods of childhood and in pregnancy, or when there is insufficient iron in the diet. Pernicious anemia, a chronic ailment that mostly affects people over 40, is a result of vitamin B 12 deficiency, often caused by decreased B12 absorption rather than a deficient diet. The most common symptoms of anemia are pallor, shortness of breath, low vitality, dizziness, and digestive disorders. Sickle-cell anemia is the result of a hereditary defect in the synthesis of hemoglobin.

Past treatment of the disease has included removal of the spleen, repeated transfusions of blood, and a diet featuring beef or calf's liver. Transfusions are still used in cases of acute blood loss; iron supplements for iron-deficiency anemia and injections of vitamin B12 for pernicious anemia are often effective. Synthetically manufactured erythropoietin (normally produced by the human kidney) is now used to stimulate the production and growth of red blood cells. Other therapy focuses on curing the underlying causes of the nutritional or hormonal deficiency.

See also Blood Diseases.

Leukemia

Leukemia, any of several types of cancers that affect blood cells, including oxygen-carrying red cells; certain infection-fighting white cells, such as granulocytes, macrophages and lymphocytes; and platelets, which aid in blood clotting.

Blood cells are made in the bone marrow, the spongy tissue in the center of bones. A leukemia begins when an immature blood cell in the marrow, known as a progenitor cell, becomes cancerous, dividing uncontrollably and overriding the body’s normal restrictions on cell division. Over time, the marrow becomes crowded with cancerous cells, all of them descendants of the first abnormal cell. The malignant cells may also accumulate in a patient’s lymph nodes, spleen, and elsewhere. At the time of diagnosis, up to a trillion leukemic cells may be present in the body.

The mass of leukemic cells in the marrow suppresses the production of healthy blood cells, giving rise to the symptoms typical of leukemia. Pale skin, fatigue, and shortness of breath are signs of anemia, a decrease in the concentration of red cells in the blood. Nose bleeds, gum bleeding, a tendency to bruise easily, and pinhead-sized red spots on the skin reflect the decrease in the concentration of platelets in the blood. A lack of functional white cells makes patients with leukemia prone to infection.

The leukemias are classified by two principal characteristics: the lineage of blood cell that becomes cancerous, and how rapidly the disease progresses. A leukemia is classified as myelocytic or myelogenous if the malignant cells have descended from the progenitors of red cells, granulocytes, macrophages, or platelets. If the leukemic cells have descended from a lymphocyte precursor cell, the leukemia is referred to as lymphocytic.

Myelocytic or lymphocytic leukemia can be acute or chronic, terms that refer to the patient’s life expectancy if the disease remains untreated. Acute leukemias develop rapidly, and without prompt treatment, the suppression of normal blood cell production is so severe that death occurs in a matter of weeks. In the chronic leukemias, patients may survive for several years or more without treatment because the effects of leukemic cells on the structure and function of the marrow develop more slowly and are less severe. In chronic myelocytic leukemia, for example, the leukemic cells can often complete their development and become functional blood cells. In chronic lymphocytic leukemia, the leukemic lymphocytes do not function normally, but in many cases the abnormal cells do not severely inhibit normal blood cell development.

The four major forms of leukemia—acute myelocytic, chronic myelocytic, acute lymphocytic, and chronic lymphocytic—can be further subcategorized based on the appearance of the malignant cells, the presence of characteristic molecules on their surface, or their stage of development. For example, hairy-cell leukemia is an uncommon type of chronic lymphocytic leukemia in which the malignant cells have fine, hairlike projections on their surface.

In most cases of leukemia, the cause is unknown, but physicians have identified four known causes of certain types of leukemia. Intensive radiation exposure or moderately intense exposure for long periods increases the risk of acute and chronic myelocytic leukemia and acute lymphocytic leukemia, but not chronic lymphocytic leukemia.

Exposure to certain chemicals can also cause leukemia. Workers exposed to benzene over long periods have an increased risk of developing acute myelocytic leukemia. Chemotherapy drugs used to treat breast cancer, ovarian cancer, lymphomas, and certain other cancers also increase a patient’s risk of later developing acute myelocytic leukemia.

Bone marrow biopsy and blood tests are the primary techniques used to diagnose leukemia. In a bone marrow biopsy, cells are collected through a hollow needle inserted into the outer edge of a hipbone, or a small cylinder of bone containing marrow is removed with a special needle. The marrow sample is examined with a microscope for the presence of leukemic cells.

Blood tests that monitor blood cell counts—the number of cells of different types in the blood—can also reveal abnormalities characteristic of various forms of leukemia. Patients with acute leukemias nearly always have decreased red cell and platelet counts. In some patients, white cell counts are also very low. In others, a large number of leukemic cells enter the blood from the bone marrow, making white cell counts very high. However, physicians can examine these cells under the microscope to determine that they are abnormal, leukemic cells, not healthy white cells, and that the elevated white cell count is not due to another cause, such as infection.

Treatment of leukemia depends on the type and extent of the disease and is tailored to each individual patient. In general, chemotherapy—the use of drugs that kill rapidly dividing cells—is the mainstay of treatment for both acute and chronic leukemias. In acute leukemias, chemotherapy is very intensive and uses several drugs, either simultaneously or sequentially, in order to kill as many leukemic cells as possible. Antibiotics and transfusions of red cells and platelets help sustain patients whose blood counts are dangerously low because they are receiving intensive chemotherapy.

Sometimes radiation is used to shrink collections of leukemic cells that accumulate in various parts of the body, such as on the lining of the brain and spinal cord in acute lymphocytic leukemia, or within lymph nodes in chronic lymphocytic leukemia. If left untreated, collections of cells on the lining of the brain and spinal cord can cause headache, blurred vision, and confusion, and elsewhere in the body can cause swelling and tenderness of the affected area.

Immunotherapy, though still in the experimental stages, is a promising new approach to treating leukemia. In this technique, highly specific molecules known as monoclonal antibodies are manufactured in the laboratory to target molecules on the surface of leukemic cells. The antibodies are attached to a radioactive substance, then injected intravenously into a patient. This method provides a convenient means of delivering the radioactive substance directly to leukemic cells, where it may kill these cells with minimal effect on healthy cells.

Rheumatology

Rheumatology is a sub-specialty in internal medicine and pediatrics, devoted to the diagnosis and therapy of rheumatic diseases. Rheumatologists mainly deal with clinical problems involving joints, soft tissues and allied conditions of connective tissues. The term rheumatology originates from the Greek word rheuma, meaning "that which flows as a river or stream" and the suffix -ology, meaning "the study of."

Rheumatology is a rapidly evolving medical specialty; new scientific discoveries related to this specialty are largely related to better understanding of immunology of these disorders. Pathogenesis of major rheumatological disorders is now described as autoimmune disorders. Immunology explains pathogenesis and the characteristics of rheumatological disorders, and most of the new treatment modalities are based on immunology, better understanding of genetic basis of rheumatological disorders makes rheumatology a specialty rapidly developing as a medical specialty based on new scientific discoveries. New treatment modalities are based on scientific research on immunology, cytokines, T lymphocytes, B lymphocytes and future therapies may be directed more towards gene therapy as well. Currently, practice of rheumatology is largely based on clinical research, evidence based medical treatment of rheumatological disorders has helped patients with rheumatism lead a near normal life without any disabilities. Clinicians who specialize in rheumatology are called Rheumatologists.

Oncology

Oncology is the branch of medicine that studies tumors (cancer) and seeks to understand their development, diagnosis, treatment, and prevention. A medical professional who practices oncology is an oncologist. The term originates from the Greek onkos (ογκος), meaning bulk, mass, or tumor and the suffix -ology, meaning "study of".

The oncologist often coordinates the multidisciplinary care of cancer patients, which may involve physiotherapy, counselling, clinical genetics, to name but a few. On the other hand, the oncologist often has to liaise with pathologists on the exact biological nature of the tumor that is being treated.

Oncology is concerned with:

• The diagnosis of cancer
• Therapy (e.g., surgery, chemotherapy, radiotherapy and other modalities)
• Follow-up of cancer patients after successful treatment
• Palliative care of patients with terminal malignancies
• Ethical questions surrounding cancer care
• Screening efforts: of populations, or of the relatives of patients (in types of cancer that are thought to have a hereditary basis, such as breast cancer).

Nephrology

Nephrology (from Greek: nephros, "kidney"; and λόγος, logos, "speech" lit. "to talk about kidney") is a branch of internal medicine and pediatrics dealing with the study of the function and diseases of the kidney.

Nephrology concerns itself with the diagnosis and treatment of kidney diseases, including electrolyte disturbances and hypertension, and the care of those requiring renal replacement therapy, including dialysis and renal transplant patients. Many diseases affecting the kidney are systemic disorders not limited to the organ itself, and may require special treatment. Examples include systemic vasculitides and autoimmune diseases such as lupus.

For more information about Nephrology, read the full articles at Wikipedia.org

Endocrinology

Endocrinology is a branch of medicine dealing with disorders of the endocrine system and its specific secretions called hormones.

Endocrinology is concerned with the study of the biosynthesis, storage, chemistry, and physiological function of hormones and with the cells of the endocrine glands and tissues that secrete them.

For more information about the topic Endocrinology, read the full articles at Wikipedia.org.

Cardiology

Cardiology is the branch of internal medicine dealing with disorders of the heart and blood vessels. The field is commonly divided in the branches of congenital heart defects, coronary artery disease, heart failure, valvular heart disease and electrophysiology. Physicians specializing in this field of medicine are called cardiologists. Cardiologists should not be confused with cardiac surgeons who are surgeons who perform cardiac surgery - operative procedures on the heart and great vessels.

For more information about the topic Cardiology, read the full articles at Wikipedia.org.

Gerontology

Gerontology is the study of the social, psychological and biological aspects of aging. It is distinguished from geriatrics, which is the branch of medicine that studies the disease of the elderly.

Gerontology includes these and other endeavors:

• studying physical, mental, and social changes in people as they age;
• investigating the aging process itself (biogerontology);
• investigating the interface of normal aging and age-related disease (geroscience);
• investigating the effects of our aging population on society, including the fiscal effects of pensions, entitlements, life and health insurance, and retirement planning;
• applying this knowledge to policies and programs, including a macroscopic (i.e. government planning) and microscopic (i.e. running a nursing home) perspective.

The multidisciplinary focus of gerontology means that there are a number of sub-fields, as well as associated fields such as psychology and sociology that also cross over into gerontology. However, that there is an overlap should not be taken as to construe that they are the same. For example, a psychologist may specialize in early adults (and not be a gerontologist) or specialize in older adults (and be a gerontologist).

Surgery

Surgery, branch of medicine concerned with treatment of diseases, deformities, and injuries through manual procedures called operations. Surgery can be used to repair broken bones, stop uncontrolled bleeding, remove injured or diseased tissue and organs, and reattach severed limbs. Exploratory surgery helps physicians diagnose conditions that cannot be detected by traditional tests. It allows for examination of internal organs for signs of disease.

People have practiced surgery since ancient times, but it did not become a respected science until the 19th century. Increasing knowledge of the human body, the discovery of anesthesia (a loss of physical sensation that can be induced with drugs), and the use of germ-free, or sterile, operating procedures combined to make surgery a safe and effective method of medical treatment. In the 20th century advances in technology have helped the field of surgery grow at a rapid pace.

Surgery is performed by specially trained medical physicians known as surgeons. General surgery training and training in some surgical specialties, such as neurosurgery, which concerns the brain, spinal cord, and peripheral nerves, and orthopedic surgery, which repairs the bones and joints, is conducted in association with a hospital and usually lasts from five to seven years. At the end of this period, known as a residency, the general surgeon may receive further training to learn the skills of a particular specialty, or subdivision, of surgery. Surgical subdivisions include, for example, thoracic surgery, which is concerned with diseases of the chest; vascular surgery, which corrects diseases of blood vessels; plastic surgery, which reconstructs or cosmetically improves features of the body; and pediatric surgery, which is concerned with operations on children.

Endoscopy

Endoscopy, examination of internal body cavities using a specialized medical instrument called an endoscope. Physicians use endoscopy to diagnose, monitor, and surgically treat various medical problems.

An endoscope is a slender, flexible tube equipped with lenses and a light source. It contains glass fibers that transmit light to illuminate the body part being viewed and fibers that reflect an image of the body part back to the viewer. The endoscope also has a channel through which surgeons can manipulate tiny instruments, such as forceps, surgical scissors, and suction devices. A surgeon introduces the endoscope into the body either through a body opening, such as the mouth or the anus, or through a small incision in the skin.

During the endoscopic procedure, the surgeon may perform several tasks. The surgeon may look for visual evidence of the problem, such as ulceration or inflammation; collect a sample of tissue; remove problematic tissue, such as polyps; or photograph the area being examined. Most endoscopic procedures are normally done with the patient lightly anesthetized.

The term endoscopy is both a general and a specialized term. As a specialized term it refers to endoscopic examination of the gastrointestinal tract. As a generalized term, endoscopy refers to examination of a wide variety of body parts. Depending on the body part, each type of endoscopy has its own special term, such as laparoscopy (abdomen), laryngoscopy (vocal cords), bronchoscopy (lungs), colonoscopy (colon), and arthroscopy (joint).