narcissistic personality disorder - a condition in which a person has severely overly inflated feelings of self-worth, grandiosity, and superiority over others. People with narcissistic personality disorder often exploit others who fail to admire them, and are overly sensitive to criticism, judgment, and defeat.
nasal - relating to the nose.
National Cancer Institute - the U.S. government agency for cancer research and information. The NCI is one of the National Institutes of Health.
nausea - a feeling or sensation leading to the urge to vomit.
near point of accommodation - the closest point in front of the eyes at which an object may be clearly focused.
near point of convergence - the maximum extent the two eyes can be turned inward.
necrosis - pertaining to the death of tissue.
needle aspiration - a procedure that uses a thin needle and syringe to collect tissue or drain a lump after using a local anesthetic.
needle biopsy - use of a needle to extract tissue, cells, or fluid for microscopic examination.
neoadjuvant therapy - treatment such as chemotherapy, radiation therapy, or hormone therapy which is given before the primary treatment.
neoplasm - any abnormal growth of new tissue; a proliferation of cells no longer under normal physiologic control. These may be benign (non-cancerous) or malignant (cancerous).
nephrectomy - surgical removal of the kidney.
nephritis - inflammation of the kidneys.
nephrology - the medical specialty concerned with diseases of the kidneys.
nephropathy - diabetic kidney disease.
nephrotic syndrome - a condition characterized by high levels of protein in the urine, low levels of protein in the blood, tissue swelling, and high cholesterol.
nerve conduction tests - procedure to determine nerve impulse generation.
nerve sparing technique - a surgical technique during a radial prostatectomy in which one or both of the neurovascular bundles controlling erections are spared.
neural plasticity - ability of the brain and/or certain parts of the nervous system to adapt to new conditions, such as an injury.
neural prostheses - devices that substitute for an injured or diseased part of the nervous system to enhance the function. Examples include cochlear implants, which can restore hearing to certain hearing-impaired people and deep brain stimulation, which can improve movement problems in people with Parkinson's disease.
neural stimulation - to activate or energize a nerve through an external source.
neural tube defect - type of birth defect, such as spina bifida, that results from failure of the spinal cord or brain to develop normally in a fetus.
neuralgia - pain in distribution of nerve or nerves.
neuritis - inflammation of a nerve or nerves.
neurofibromatosis - a group of inherited disorders in which non-cancerous tumors grow along several nerves; can affect the development of other tissues, including bones and skin, possibly leading to developmental abnormalities.
neurogenic - of nerve origin.
neurogenic bladder (Also called neuropathic bladder.) - a bladder disorder in which the bladder cannot be completely emptied of urine because of a problem with the nerves connected to the bladder. It can be caused by a tumor or other condition of the nervous system.
neurogenic communication disorder - inability to exchange information with others because of hearing, speech, and/or language problems caused by impairment of the nervous system.
neurological - pertaining to the nervous system.
neuron - a cell specialized to conduct and generate electrical impulses and to carry information from one part of the brain to another.
neuropathology - the pathology of the nervous system.
neuropathy - nerve damage caused by the effects of diabetes.
neurosonography - the use of ultrasound (high-frequency sound waves) technology to assess neurological conditions.
neurotransmitters - chemical substances that carry impulses from one nerve cell to another; found in the space (synapse) that separates the transmitting neuron's terminal (axon) from the receiving neuron's terminal (dendrite).
nigral - of or referring to the substantia nigra.
nitroglycerin - a medication used to relax or dilate arteries.
nodule (Also called papule.) - a solid, raised bump.
noise-induced hearing loss - hearing loss that is caused either by a one-time or repeated exposure to very loud sound or sounds at various loudness levels over an extended period of time.
non-Hodgkin lymphoma - a type of lymphoma, a cancer in the lymphatic system; causes the cells in the lymphatic system to abnormally reproduce, eventually causing tumors to grow. Non-Hodgkin lymphoma cells can also spread to other organs.
noninvasive procedure - a diagnostic effort or treatment that does not require entering the body or puncturing the skin.
nonsteroidal anti-inflammatory drugs (NSAIDs) - medications that produce fever reducing, analgesic (pain relieving), and anti-inflammatory effects. Examples of NSAIDs include ibuprofen (Motrin, Advil) and naproxen (Aleve).
nonsyndromic hereditary hearing impairment - hearing loss or deafness that is inherited and is not associated with other inherited clinical characteristics.
nonulcer dyspepsia - constant pain or discomfort in the upper gastrointestinal (GI) tract that is not caused by an ulcer.
norepinephrine - a neurotransmitter found mainly in areas of the brain that are involved in governing autonomic nervous system activity, especially blood pressure and heart rate.
nuclear medicine - a specialized area of radiology that uses very small amounts of radioactive substances to examine organ function and structure.
Nutcracker syndrome - a condition caused by compression of the renal vein between the abdominal aorta and the superior mesenteric artery. This can lead to problems such as blood in the urine.
nutrients - proteins, carbohydrates, fats, vitamins, and minerals provided by food and necessary for growth and the maintenance of life.
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