Definition Rhythmic, oscillating motions of the eyes are called nystagmus. The to-and-fro motion isgenerally involuntary. Vertical nystagmus occurs much less frequently than horizontal nystagmus and is often, but not necessarily, a sign of serious brain damage. Nystagmus can be a normal physiological response or a result of a pathologic problem. Description The eyes play a critical role in maintaining...

Definition Nutritional supplements, also called dietary supplements , include vitamins , minerals, herbals, botanicals, amino acids, enzymes, and animal extracts. The U.S. Food and Drug Administration (FDA) defines them as food rather than drugs, and regulates their labeling as such—to be used as supplements and not as drugs. Nutritional supplements come...

  Definition Sterile solutions containing some or all of the nutrients necessary to support life, are injected into the body through a tube attached to a needle, which is inserted into a vein, either temporarily or for long-term treatment. Purpose Patients who cannot consume enough nutrients or who cannot eat at all due to an illness, surgery, or accident, can be fed through an intravenous (IV) line or...

  Definition Good nutrition can help prevent disease and promote health. There are six categories of nutrients that the body needs to acquire from food: protein, carbohydrates, fat, fibers, vitamins and minerals, and water. Proteins Protein supplies amino acids to build and maintain healthy body tissue. There are 20 amino acids considered essential because...

Definition Numbness and tingling are decreased or abnormal sensations caused by altered sensory nerve function. Description The feeling of having a foot "fall asleep" is a familiar one. This same combination of numbness and tingling can occur in any region of the body and may be caused by a wide variety of disorders. Sensations such as these, which occur without any associated...

Definition A nosebleed, also called epistaxis, is a loss of blood from any blood vessel in the nose. It usually appears in only one nostril. Description Although unexpected or persistent bleeding from anywhere is a warning sign of cancer and should be investigated, nosebleeds are rarely a sign of serious illness. They are usually the result of minor injury or irritation. Nosebleeds most often...

Definition Noroviruses are a group of related, single-stranded RNA (ribonucleic acid) viruses that cause acute gastroenteritis in humans. Description Noroviral infection Noroviruses are a major cause of viral gastroenteritis—an inflammation of the linings of the stomach and small and large intestines that causes vomiting and diarrhea. Viruses are responsible for 30-40%...

Definition Nonsteroidal antiinflammatory drugs (NSAIDs) reduce pain and inflammation. Purpose NSAIDs often are used to relieve mild to moderate pain for all types of cancer. Description This class of drugs eases discomfort by blocking the pathway of an enzyme that creates prostaglandins (hormones that cause pain and swelling). By doing so, the drugs lessen the pain in different...

Definition Any inflammation of the urethra not due to gonorrhea, almost always contracted through sexual intercourse and found far more often in men. Description Men between the ages of 15 and 30 who have multiple sex partners are most at risk for nongonococcal urethritis (NGU), which is believed to be the most common sexually transmitted disease in the United States. Causes and symptoms NGU is spread...

Definition This type of drug interferes with an enzyme that is key to the replication (reproduction) of the human immunodeficiency virus (HIV). The drug is designed to help suppress the growth of HIV, but does not eliminate it. Purpose This medication is used to treat patients with the HIV virus and AIDS in combination with one or more other AIDS drugs. Combining NRTIs with older drugs improves...

Definition Nocardiosis is a serious infection caused by a fungus-like bacterium that begins in the lungs and can spread to the brain. Description Nocardiosis is found throughout the world among people of all ages, although it is most common in older people and males. While people with poor immunity are vulnerable to this infection, it sometimes strikes individuals with no history of other diseases. Nocardiosis is...

Definition Nitrogen narcosis is a condition that occurs in divers breathing compressed air. When divers go below depths of approximately 100 ft, increase in the partial pressure of nitrogen produces an altered mental state similar to alcohol intoxication. Description Nitrogen narcosis, commonly referred to as "rapture of the deep," typically becomes noticeable at 100 ft underwater...

Definition Night terrors are a sleep disorder characterized by anxiety episodes with extreme panic,often accompanied by screaming, flailing, fast breathing, and sweating and that usually occur within a few hours after going to sleep. Description Night terrors occur most commonly in children between the ages of four and 12 but can also occur at all ages. Affected individuals usually suffer these episodes within...

Definition Neutropenia is an abnormally low level of neutrophils in the blood. Neutrophils are white blood cells (WBCs) produced in the bone marrow that ingest bacteria. Neutropenia is sometimes called agranulocytosis or granulocytopenia because neutrophils make up about 60% of WBCs and have granules inside their cell walls. Neutropenia is a serious disorder because it makes the body...

Definition A neurological examination is an essential component of a comprehensive physical examination. It is a systematic examination that surveys the functioning of nerves delivering sensory information to the brain and carrying motor commands (peripheral nervous system) and impulses back to the brain for processing and coordinating (central nervous system). Purpose A careful neurological evaluation can help...

Definition Neurolinguistic programming (NLP) is aimed at enhancing the healing process by changing the conscious and subconscious beliefs of patients about themselves, their illnesses, and the world. These limiting beliefs are "reprogrammed" using a variety of techniques drawn from other disciplines including hypnotherapy and psychotherapy. Purpose Neurolinguistic programming has...

Definition Neurogenic bladder is a dysfunction that results from interference with the normal nerve pathways associated with urination. Description Normal bladder function is dependent on the nerves that sense the fullness of the bladder (sensory nerves) and on those that trigger the muscle movements that either empty it or retain urine (motor nerves). The reflex to urinate is triggered...

Neurofibromatosis (noor-o-fy-bro-ma-TO-sis) is a genetic disorder that causes tumors to grow on nerves and is also characterized by skin changes and deformities in bone. KEYWORDS for searching the Internet and other reference sources Inherited Genetic Disorders Neurology   What Is Neurofibromatosis? The most common form, called neurofibromatosis type 1 or NF-1, mainly affects nerves...

Definition Neuroendocrine tumor refers to the type of cell that a tumor grows from rather than where that tumor is located. Neuroendocrine cells produce hormones or regulatory proteins, and so tumors of these cells usually have symptoms that are related to the specific hormones that they produce. Description Neuroendocrine cells have roles both in the endocrine system and the nervous...

Definition Neuroblastoma is a type of cancer that usually originates either in the tissues of the adrenal gland or in the ganglia of the abdomen or in the ganglia of the nervous system. (Ganglia are masses of nerve tissue or groups of nerve cells.) Tumors develop in the nerve tissue in the neck, chest, abdomen, or pelvis. Description Neuroblastoma is one of the few cancer types known to secrete...

Definition Neuralgia describes a variety of rare and painful conditions in which shooting, stabbing, burning, pain; electric-like shocks; or tingling, pins and needles, or numbness occur along the course of a nerve, usually in the head or neck. Description Neuralgia attacks tend to by cyclic, often coming and going without warning. They can last for minutes, hours, days, or longer, depending on the...

Definition Nephrotoxic injury is damage to one or both of the kidneys that results from exposure to a toxic material, usually through ingestion. Description The kidneys are the primary organs of the urinary system, which purifies the blood by removing wastes from it and excreting them from the body in urine. Every day, the kidneys filter about 45 gal (180 l) of blood, about four times as much as the...

Definition Nephrotic syndrome is a collection of symptoms which occur because the tiny blood vessels (the glomeruli) in the kidney become leaky. This allows protein (normally never passed out in the urine) to leave the body in large amounts. Description The glomeruli (a single one is called a glomerulus) are tiny tufts of capillaries (the smallest type of blood vessels). Glomeruli are located in the...

Definition Nephritis is inflammation of the kidney. Description The most prevalent form of acute nephritis is glomerulonephritis. This condition affects children and teenagers far more often than it affects adults. It is inflammation of the glomeruli, or small round filters located in the kidney. Pyelonephritis affects adults more than children, and is recognized as inflammation...

Definition Nephrectomy is the surgical procedure of removing a kidney or section of a kidney. Purpose Nephrectomy, or kidney removal, is performed on patients with cancer of the kidney (renal cell carcinoma); a disease in which cysts (sac-like structures) displace healthy kidney tissue (polycystic kidney disease ); and serious kidney infections. It is also used to remove a healthy kidney...

Definition Neonatal jaundice is the term used when a newborn has an excessive amount of bilirubin in the blood. Bilirubin is a yellowish-red pigment that is formed and released into the bloodstream when red blood cells are broken down. Jaundice comes from the French word jaune, which means yellow; thus a jaundiced baby is one whose skin color appears yellow due to bilirubin. Description Normally,...

Definition Necrotizing enterocolitis (NEC) is a serious bacterial infection in the intestine, primarily affecting sick or premature newborn infants. It can cause the death (necrosis) of intestinal tissue and progress to blood poisoning (septicemia). Description Necrotizing enterocolitis is a serious infection that can produce complications in the intestine itself such as ulcers, perforations...

Definition Near-drowning is the term for survival after suffocation caused by submersion in water or other fluid. Some experts exclude from this definition cases of temporary survival that end in death within 24 hours, which they prefer to classify as drownings. Description Drowning is always fatal, but near-drowning may result in survival with no long-lasting effects; survival with permanent...

Definition Nausea is the sensation of being about to vomit. Vomiting, or emesis, is the expelling of undigested food through the mouth. Description Nausea is a reaction to a number of causes that include overeating, infection, or irritation of the throat or stomach lining. Persistent or recurrent nausea and vomiting should be checked by a doctor. A doctor should be called if nausea and vomiting occur: ·        ...

Definition Naturopathic medicine is a branch of medicine in which a variety of natural medicines and treatments are used to heal illness. It uses a system of medical diagnosis and therapeutics based on the patterns of chaos and organization in nature. It is founded on the premise that people are naturally healthy, and that healing can occur through removing obstacles to a cure and by stimulating...

Definition A nasopharyngeal culture is a microbiology test used to identify pathogenic organisms present in the nasal cavity that may be the cause of an upper respiratory tract illness or may be transmitted by carriers to persons susceptible to infection. Purpose Some of the organisms responsible for upper respiratory infections are carried primarily in the nasopharynx. Nasopharyngeal cultures...

Definition Nasogastric suction involves removing solids, liquids, or gasses from the stomach or small intestine by inserting a tube through the nose and suctioning the gastrointestinal material through the tube. Purpose Nasogastric suction may be done in the following situations: ·         to decompress the stomach or small intestine when intestinal...

Definition Nasal trauma is defined as any injury to the nose or related structure that may result in bleeding, a physical deformity, a decreased ability to breathe normally because of obstruction, or an impaired sense of smell. The injury may be either internal or external. Description The human nose is composed of bone, soft tissue, and cartilage. It serves as a passageway for air to flow from the...

Definition A polyp is the medical term for any overgrowth of tissue from the surface of a body organ. Polyps come in all shapes—round, droplet, and irregular being the most common. Nasal polyps are teardrop-shaped while growing and resemble peeled grapes when they have reached their full size. The condition of nasal polyps is sometimes called nasal polyposis. Description Nasal polyps tend...

Definition Nasal papillomas are warts located inside the nose. Description Two types of tumors can grow inside the nose: polyps and papillomas. By far the most common are polyps, which have smooth surfaces. On the contrary, papillomas have irregular surfaces and are, in fact, warts. Papillomas may be caused by the same viruses that cause warts elsewhere on the body....

Definition Nasal packing is gauze, foam, or cotton that has been packed into the nasal chambers. The term nasal packing may refer to individual gauze strips or cotton pledgets that are packed as they are inserted into the nose to form a plug or may refer to a preshaped pack of foam, gauze, or cotton that is inserted into the nose as a unit. Nasal packing may be coated...

Definition Nasal irrigation is the practice of flushing the nasal cavity with a sterile solution. The solution may contain antibiotics or steroid medications. Purpose Nasal irrigation is used to clear infected sinuses or may be performed after surgery to the nose region. It may be performed by adding antibiotics to the solution to treat nasal polyps, nasal septal...

A narcotic is a substance that produces insensibility, or a stuporous state. The most notable characteristics of narcotics are their ability to decrease the perception of pain and alter the reaction to pain, and their extremely addictive properties. Narcotics often induce a state of euphoria or extreme well being. The word narcotic is derived from the Greek word narké (meaning stupor),...

Definition Narcolepsy is a disorder of the nervous system marked by excessive daytime sleepiness, uncontrollable sleep attacks, and cataplexy (a sudden loss of muscle tone, usually lasting up to half an hour). The American Psychiatric Association (APA) classifies narcolepsy as a sleep disorder in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders, or DSM-IV....

Definition Nail removal is a form of treatment that is sometimes necessary following traumatic injuries or recurrent infections in the area of the nail. There are nonsurgical as well as surgical methods of nail removal. Purpose Nails are removed only when necessary to allow the skin beneath the nail (the nail bed) to heal or in some cases, to remove a nail that...

Definition Nail-patella syndrome is a genetic disease of the connective tissue that produces defects in the fingernails, bone joints, and kidneys. Description Patients who have nail-patella syndrome may show a variety of physical defects. The most common features of this syndrome are missing or poorly developed fingernails, toenails, and patellae (kneecaps). Other common abnormalities...

There are several possible causes for blockage of air in one or both nostrils. Except for the common cold, perhaps the most frequent cause for nasal obstruction in children is an enlargement of the adenoid tissue which may press against the openings from the nasal cavities into the pharynx. This causes mouth breathing, especially at night, and predisposes to a change in the shape of the face. Hay fever commonly...

The cause of nervousness may be either psychological or physical. Psychological causes include emotional conflicts, lack of a goal in life, lack of a sense of belonging, an awareness of thwarted ambition, or mental, depression. Nervousness is often associated with fatigue. Nervousness often occurs in connection with an overactive thyroid. It may accompany chronic systemic diseases such as tuberculosis. It...

The common type of stiff neck from which a person suffers after" sleeping in the wrong position" or after being exposed to cold is an example of fibrositis. The cause is probably continued muscle tension which reduces the blood supply to the involved muscles. The same malady may cause muscle pain in the shoulder or lower back. A more chronic form of stiff neck occurs in torticollis (wry neck) which...

See Lymphadenopathy Masses in the neck are commonly caused by enlargement of the lymph nodes, thyroid gland, or salivary glands. Congenital cysts and benign fatty tumors can also produce local enlargements. Enlargements of the lymph nodes are mentioned in this chapter under Lymphadenopathy. Enlargements of the thyroid gland occur in the various forms of goiter, in thyroiditis, and in cancer of the thyroid...

(See Dyspepsia) The causes of nausea and vomiting are as follows: 1. Psychic Reactions. Emotional shock (as sudden bad news), pain, fright, grief, unpleasant tastes, and offensive smells may trigger the vomiting mechanism. 2. Drugs. Some drugs produce vomiting by irritating the lining of the digestive organs; others, by directly influencing the vomiting center in the brain. 3. Poisons. Nausea and vomiting...