Health A-Z


Clinical Definition Narcolepsy is a chronic neurological disorder that interferes with a person’s sleep-wake cycle. In Our Own Words People who have the sleep disorder, narcolepsy, often fall asleep uncontrollably, even after having adequate sleep. During the day, you may be excessively sleepy and nearly unable to function. Sleep attacks can occur even when narcoleptics

Nasal Polyps

Clinical Definition Nasal polyps are small growths of inflamed tissue that are noncancerous and can develop on the nasal mucosa or paranasal sinuses. They are associated with prolonged inflammation of the nasal passages or sinuses from conditions such as chronic sinusitis, allergic rhinitis and asthma. If nasal polyps become too large, they can obstruct the


Clinical Definition Necrosis is the localized death of living tissue caused by lack of blood or oxygen and cannot be attributed to programmed cell death. In Our Own Words Necrosis is when cells die due to lack of oxygen or blood, rather than a normal, programmed cell death. Necrosis can be caused by many factors,

Nephrotic Syndrome

Clinical Definition Nephrotic syndrome, a collection of symptoms and laboratory findings that indicate renal damage, is marked by heavy protein in the urine, peripheral edema and hypoalbuminemia. Hyperlipidemia and thrombotic disease are also common. In adults, renal or systemic disease such as diabetes may be the cause; in children, minimal change disease is the major

Nervous Breakdown

Clinical Definition A nervous breakdown is technically not a medical term, but is frequently used to describe a feeling of overwhelming anxiety and stress, such that a patient is unable to maintain their previous normal level of functioning. It is commonly considered apart from any psychiatric diagnosis such as bipolar disorder, and individuals suffering from

Neti Pot

Clinical Definition A neti pot is a device used to irrigate the nasal passages and sinuses. Through the device, a saline solution is introduced into the nasal cavity in order to assist in mucociliary clearance. The solution allows allergens to be removed from the nose and sinuses. Using a neti pot may reduce nasal dryness


Clinical Definition Neuropathy, also called peripheral neuropathy, describes damage to the peripheral nervous system—a network of nerves that connects the brain and spinal cord to the rest of the body. Neuropathy may be acquired from trauma, infection or systemic disease, or may be caused by medications, blood vessel problems or alcoholism. Charcot-Marie-Tooth disease is the

Nicotine Withdrawal

Clinical Definition Nicotine withdrawal occurs when someone dependent on nicotine ceases tobacco use. Nicotine is possibly as addictive as heroin, cocaine or alcohol. Withdrawal symptoms may include irritability, anxiety, concentration difficulties, insomnia and increased appetite and are linked with the level and extent of tobacco use. To relieve withdrawal symptoms medications can be prescribed. In

Night Terrors

Clinical Definition Night terrors are a type of parasomnia in which a person seems to awaken, typically from stage 3 deep sleep, in a terrified state. Those affected may appear to be awake, but also appear confused and are unable to communicate. Typically, a night terror continues for about 15 minutes, with the person then


Clinical Definition Nocturia is a fairly common condition in which a patient has to wake up at night to void the bladder (i.e., urinate). In Our Own Words Most people can sleep six to eight hours without needing to urinate, but patients with nocturia awaken at least once — and frequently, many additional times —

Nocturnal polyuria

Clinical Definition Nocturnal polyuria is an excessive volume of urination at nighttime. Etiologies include, excessive fluid intake (especially of caffeine or alcohol), congestive heart failure, renal insufficiency, and other conditions. Diagnosis depends on a careful health history, physical exam, evaluation of a voiding diary, tests such as urinalysis and urodynamic tests; treatment includes treating underlying

Nodules, Lung

Clinical Definition A lung nodule is a rounded opacity surrounded by lung parenchyma. It is equal to or less than 3 centimeters in diameter and usually well marginated. Lung nodules may be benign tumors, such as a hamartoma or a malignancy. Growths larger than 3 centimeters are generally classified as masses and suspected to be

Non-Hodgkin Lymphoma

Clinical Definition Non-Hodgkin lymphoma is a group of hematologic malignancies that originate in the lymphocytes. The cancerous lymphocytes multiply and do not function normally, compromising immune system functions. There are many subtypes of non-Hodgkin’s lymphoma classified according to whether they arise from T cells or B cells and whether they are indolent or aggressive. In Our Own Words

Non-Steroidal Anti-Inflammatory Drug

Clinical Definition Non-steroidal anti-inflammatory medications, or NSAIDs, are commonly recommended to relieve pain and decrease inflammation (the body’s response to injury or irritation, marked by warmth, pain, swelling). They work by blocking production of inflammatory triggers. Besides helping to reduce fever, subdue a headache or ease minor aches caused by a cold, NSAIDs are often


Clinical Definition Triggered by a group of Calicivirus viruses, norovirus is a viral infection that causes gastroenteritis. It is highly contagious and can be transmitted through drinking contaminated water or eating contaminated food or undercooked shellfish. In Our Own Words Norovirus is a contagious infection that causes vomiting, diarrhea and gastroenteritis (i.e., inflammation of the

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