near point of accommodation - the closest point in front of the eyes that an object may be clearly focused.  

near point of convergence - the maximum extent the two eyes can be turned inward.

needle aspiration (of the breast) - uses a thin needle and syringe to collect tissue or drain a lump after using a local anesthetic.

needle biopsy - biopsy procedure in which a small sample of tissue is removed through a hollow needle.

neoadjuvant therapy - chemotherapy given before surgery or radiation therapy.

nephrectomy - surgical removal of the kidney.  

nephropathy - diabetic kidney disease.

nerve conduction test - procedure to determine nerve impulse generation.

nerve sparing technique - a surgical technique often used during a radial prostatectomy in which one or both of the neurovascular bundles controlling erections are spared.

neural mobilization - techniques by which neural tissues are moved, either by movement relative to their surroundings or by tension development.

neural plasticity - ability of the brain and/or certain parts of the nervous system to change in order 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.

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 - a painful condition caused by disorders of the nervous system. 

neuritis - inflammation of a nerve or nerves.

neurofibromatosis (Von Recklinghausen's) - a group of inherited disorders in which noncancerous tumors grow on several nerves that may include the hearing nerve.

neurogenic - of nerve origin.

neurogenic communication disorder - inability to exchange information with others because of hearing, speech, and/or language problems caused by impairment of 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 study of the nervous system.  

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).

Nissen fundoplication - operation to sew the top of the stomach (fundus) around the esophagus; used to stop stomach contents from flowing back into the esophagus (reflux) and to repair a hiatal hernia.

noise-induced hearing loss - hearing loss that is caused either by a one-time or repeated exposure to very loud sound(s).

noninvasive procedures - a diagnostic effort or treatment that does not require entering the body or puncturing the skin.

non-steroidal anti-inflammatory drugs (NSAIDs) - medications that produces antipyretic, analgesic, and anti-inflammatory effects.

nonulcer dyspepsia - constant pain or discomfort in the upper gastrointestinal tract.

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.

Norwalk virus - virus that may cause gastrointestinal (GI) infection and diarrhea. (See also gastroenteritis.)

nuclear medicine - a specialized area of radiology that uses very small amounts of radioactive substances to examine organ function and structure.

nutrients - proteins, carbohydrates, fats, vitamins, and minerals provided by food and necessary for growth and the maintenance of life.