Definition A myxoma is a rare, usually noncancerous, primary tumor (a new growth of tissue) of the heart. It is the most common of all benign heart tumors. Description Myxoma is an intracardiac tumor; it is found inside the heart. Seventy five percent of all myxomas are found in the left atrium, and almost all other myxomas are found in the right atrium. It is very rare for a myxoma to...

Definition Myringotomy is a surgical procedure in which a small incision is made in the eardrum (the tympanic membrane), usually in both ears. The English word is derived from myringa, modern Latin for drum membrane, and tome, Greek for cutting. It is also called myringocentesis, tympanotomy, tympanostomy, or paracentesis of the tympanic membrane. Fluid in the middle ear can...

Definition Myotonic dystrophy is a progressive disease in which the muscles are weak and are slow to relax after contraction. Description Myotonic dystrophy (DM), also called dystrophia myotonica, myotonia atrophica, or Steinert's disease, is a common form of muscular dystrophy. DM is an inherited disease, affecting males and females approximately equally. About 30,000...

Definition Myositis is a rare disease in which the muscle fibers and skin are inflamed and damaged, resulting in muscle weakness. There are several types of myositis that affect different parts of the body. Description The persistent inflammation that is associated with myositis develops slowly over weeks to months and often years, with progressive weakening of the muscles. Later in...

Definition Myopia is the medical term for nearsightedness. People with myopia see objects more clearly when they are close to the eye, while distant objects appear blurred or fuzzy. Reading and close-up work may be clear, but distance vision is less sharply defined. Description To understand myopia it is necessary to have a basic knowledge of the main parts of the eye's...

Definition Myopathies are diseases of skeletal muscle which are not caused by nerve disorders. These diseases cause the skeletal or voluntary muscles to become weak or wasted. Description There are many different types of myopathies, some of which are inherited, some inflammatory, and some caused by endocrine problems. Myopathies are rare and not usually fatal. Typically, effects are mild,...

Definition Myomectomy is the removal of fibroids (noncancerous tumors) from the wall of the uterus.Myomectomy is the preferred treatment for symptomatic fibroids in women who want to keep their uterus. Larger fibroids must be removed with an abdominal incision, but small fibroids can be taken out using laparoscopy or hysteroscopy. Purpose A myomectomy can remove uterine...

Definition Myoglobin is a protein found in muscle. Myoglobin tests are done to evaluate a person who has symptoms of a heart attack (myocardial infarction) or other muscle damage. Purpose Myoglobin holds oxygen inside heart and skeletal muscle (muscles that attach to and move bones). It is continually released into the blood in small amounts due to normal turnover of muscle cells....

Definition Myocarditis is an inflammatory disease of the heart muscle (myocardium) that can result from a variety of causes. While most cases are produced by a viral infection, an inflammation of the heart muscle may also be instigated by toxins, drugs, and hypersensitive immune reactions. Myocarditis  is a rare but serious condition that affects both males and females of any age. Description Most...

Definition Myocardial resection is a surgical procedure in which a portion of the heart muscle is removed.  Purpose Myocardial resection is done to improve the stability of the heart function or rhythm. Also known as endocardial resection, this open-heart surgery is done to destroy or remove damaged areas. These areas can generate life-threatening heart rhythms. Conditions resulting...

Definition Myocardial biopsy is a procedure wherein a small portion of tissue is removed from the heart muscle for testing. This test is also known as endomyocardial biopsy. Purpose The main reason for a biopsy is to secure tissue samples that will be useful in the diagnosis, treatment, and care of heart muscle disorders. The test is also used to detect rejection after a heart transplantation procedure. Precautions This...

Definition The Myers-Briggs Type Indicator (MBTI) is a widely-used personality inventory, or test, employed in vocational, educational, and psychotherapy settings to evaluate personality type in adolescents and adults age 14 and older. Purpose In an educational setting, the MBTI may be performed to assess student learning style. Career counselors use the test to help others determine...

Definition Myelography is an x-ray examination of the spinal canal. A contrast agent is injected through a needle into the space around the spinal cord to display the spinal cord, spinal canal, and nerve roots on an x ray.  Purpose The purpose of a myelogram is to evaluate the spinal cord and nerve roots for suspected compression. Pressure on these delicate structures causes pain or other symptoms....

Definition Myelofibrosis is a rare disease of the bone marrow in which collagen builds up fibrous scar tissue inside the marrow cavity. This is caused by the uncontrolled growth of a blood cell precursor, which results in the accumulation of scar tissue in bone marrow. Myelofibrosis goes by many names including idiopathic myelofibrosis, agnogenic myeloid metaplasia, chronic myelosclerosis,...

Definition Myelodysplastic syndrome (MDS) is a disease that is associated with decreased production of blood cells. Blood cells are produced in the bone marrow, and the blood cells of people with MDS do not mature normally. There are three major types of blood cells —red blood cells, white blood cells and platelets. Patients with MDS can have decreased production of one, two, or all three...

Definition Mycoplasma are the smallest of the free-living organisms. (Unlike viruses, mycoplasma can reproduce outside of living cells.) Many species within the genus Mycoplasma thrive as parasites in human, bird, and animal hosts. Some species can cause disease in humans. Description Mycoplasma are found most often on the surfaces of mucous membranes. They...

Definition Atypical mycobacterial infections are infections caused by several types of mycobacteriasimilar to the germ that causes tuberculosis. These atypical mycobacterial infections are a frequent complication in patients with human immunodeficiency virus (HIV) infection or AIDS. Description Mycobacteria are a group of rod-shaped bacteria that cause several diseases, among them leprosy and...

Definition Mycetoma, or maduromycosis, is a slow-growing bacterial or fungal infection focused in one area of the body, usually the foot. For this reason—and because the first medical reports were from doctors in Madura, India—an alternate name for the disease is Madura foot. The infection is characterized by an abnormal tissue mass beneath the skin, formation of cavities within the mass, and a fluid...

Definition Myasthenia gravis (MG) is a chronic autoimmune disease characterized by fatigue and muscular weakness, especially in the face and neck, that results from a breakdown in the normal communication between nerves and muscles caused by the deficiency of acetylcholine at the neuromuscular (nerve-muscle) junctions. MG is the most common primary disorder of neuromuscular transmission. Description MG...

Definition Mutism is a rare childhood condition characterized by a consistent failure to speak in situations where talking is expected. Description In mutism, the child has the ability to converse normally and does so, for example, in the home, but consistently fails to speak in specific situations such as at school or with strangers. The condition is also called selective mutism, to differentiate...

  Definition Music therapy is the clinical use of music or music-making to assist the physical, spiritual, cognitive, or social needs of individual patients or groups. It can be used with people of all ages and in a wide variety of settings ranging from outpatient clinics and rehabilitation centers to schools, hospices, and prisons. In addition, music therapy can...

  Definition Mushroom poisoning refers to the severe and often deadly effects of various toxins that are found in certain types of mushrooms. One type known as Amanita phalloides, appropriately called "death cap," accounts for the majority of cases. The toxins initially cause severe abdominal cramping,vomiting, and watery diarrhea, and then lead to liver and kidney...

Definition Muscular dystrophy is the name for a group of inherited disorders in which strength and muscle bulk gradually decline. Nine types of muscular dystrophies are generally recognized. Description The muscular dystrophies include: ·         Duchenne muscular dystrophy (DMD). DMD affects young boys, causing progressive...

Definition Muscle spasms and cramps are spontaneous, often painful muscle contractions. Description The rapid, uncontrolled muscle contraction, or spasm, happens unexpectedly, with either no stimulation or some trivially small one. The muscle contraction and pain last for several minutes and then slowly ease. Cramps may affect any muscle but...

Muscle relaxants are drugs that are administered to relieve the discomfort of muscle spasm or involuntary muscle contracture and also in cases of surgery to relax muscles and provide easier access for the surgeon. Some nonprescription drugs are available to combat painful contraction of the uterus during a woman’s menstrual period. The muscle relaxant cyclobenzaprine...

Definition Munchausen syndrome is a psychiatric disorder that causes an individual to self-inflict injury or illness or to fabricate symptoms of physical or mental illness in order to receive medical care or hospitalization . In a variation of the disorder, Munchausen by proxy (MSBP), an individual, typically a mother, intentionally causes or fabricates illness in a child or other person...

Definition Mumps is a relatively mild short-term viral infection of the salivary glands that usually occurs during childhood. Typically, mumps is characterized by a painful swelling of both cheek areas, although the person could have swelling on one side or no perceivable swelling at all. The salivary glands are also called the parotid glands, therefore, mumps is sometimes referred to as an inflammation of the...

Definition Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system . The disease results in injury to the myelin sheath (the fatty matter that covers the axons of the nerve cells), the oligodendrocytes (the cells that produce myelin) and, to a lesser extent, the axons and nerve cells themselves. The symptoms of multiple sclerosis vary, depending...

  Definition Multiple pregnancy is a pregnancy where more than one fetus develops simultaneously in the womb. Description Twins happen naturally about one in every 100 births. There are two types of twinning—identical and fraternal. Identical twins represent the splitting of a single fertilized zygote (union of two gametes or male/female sex cells that produce a developing fetus)...

Multiple personality disorder (MPD) is a chronic and recurrent emotional illness. A person with MPD plays host to two or more personalities. Each identity has its own unique style of viewing and understanding the world and may have its own name. These distinct personalities periodically control that person’s behavior as if several people were alternately sharing the same body. Because those...

Definition Multiple myeloma is a cancer in which antibody-producing plasma cells grow in an uncontrolled and invasive (malignant) manner. Description Multiple myeloma, also known as plasma cell myeloma, is the second-most common cancer of the blood. It is the most common type of plasma cell neoplasm. Multiple myeloma accounts for approximately 1% of all cancers and...

Definition The multiple endocrine neoplasia (MEN) syndromes are three related disorders in which two or more of the hormone-secreting (endocrine) glands of the body develop tumors. Commonly affected glands are the thyroid, parathyroids, pituitary, adrenals, and pancreas. Two common cancers are medullary thyroid cancer and gastrinomas. MEN is sometimes called familial multiple endocrineneoplasia (FMEN)...

Definition Multiple chemical sensitivity—also known as MCS syndrome, environmental illness, idiopathic environmental intolerance, chemical AIDS , total allergy syndrome, or simply MCS—is a disorder in which a person develops symptoms from exposure to chemicals in the environment. With each incidence of exposure, lower levels of the chemical will trigger a reaction...

Definition The multiple-gated acquisition (MUGA) scan is a non-invasive nuclear test that uses a radioactive isotope called technetium to evaluate the functioning of the heart's ventricles. Purpose The MUGA scan is performed to determine if the heart's left and right ventricles are functioning properly and to diagnose abnormalities in the heart wall. It can be ordered...

Definition Mucormycosis is a rare but often fatal disease caused by certain fungi. It is sometimes called zygomycosis or phycomycosis. Mucormycosis is an opportunistic infection that typically develops in patients with weakened immune systems, diabetes, kidney failure, organ transplants, or chemotherapy for cancer. It may also develop in patients receiving an iron chelating drug...

Definition Mucopolysaccharidosis (MPS) is a general term for a number of inherited diseases that are caused by the accumulation of mucopolysaccharides, resulting in problems with an individual's development. With each condition, mucopolysaccharides accumulate in the cells and tissues of the body because of a deficiency of a specific enzyme. The specific enzyme that is deficient or absent is what distinguishes...

Definition Movement therapy refers to a broad range of Eastern and Western movement approaches used to promote physical, mental, emotional, and spiritual well-being. Some forms of movement therapy that combine deep-tissue manipulation and postural correction with movement education are also known as bodywork therapies. Origins Movement is fundamental to human life....

Definition Movement disorders are a group of diseases and syndromes affecting the ability to produce and control bodily movements. Description It seems simple and effortless, but normal movement requires an astonishingly complex system of control. Disruption of any portion of this system can cause a person to produce movements that are too weak, too forceful,...

  Definition Motion sickness is uncomfortable dizziness , nausea , and vomiting that people experience when their sense of balance and equilibrium is disturbed because their brain cannot make sense of conflicting information about their body's location in space and motion in their environment. Description Motion sickness is...

Definition Mood disorders are mental disorders characterized by periods of depression, sometimes alternating with periods of elevated mood. Description While many people go through sad or elated moods from time to time, people with mood disorders suffer from severe or prolonged mood states that disrupt their daily functioning. Among the generalmood disorders classified...

Definition Monoamine oxidase inhibitors (MAO inhibitors) are medicines that relieve certain types of mental depression. Purpose MAO inhibitors are a type of antidepressant and are used to treat mental depression. Like other antidepressant drugs, MAO inhibitors help reduce the extreme sadness, hopelessness, and lack of interest in life that are typical in people with...

Definition Monkeypox is an infectious disease caused by an orthopoxvirus. Orthopoxviruses are a genus of viruses that include the disease agents that cause human smallpox, cowpox, and camelpox as well as monkeypox. Monkeypox, which was first identified in humans in an outbreak in Africa in 1970, usually produces a less severe illness with fewer fatalities...

Definition A mole (nevus) is a pigmented (colored) spot on the outer layer of the skin (epidermis). Description Moles can be round, oval, flat, or raised. They can occur singly or in clusters on any part of the body. Most moles are brown, but colors can range from pinkish flesh tones to yellow, dark blue, or black. A mole usually lasts about 50 years before beginning to fade. Some moles disappear...

Definition The term stenosis means an abnormal narrowing of an opening. Mitral valve stenosis refers to a condition in the heart in which one of the valve openings has become narrow and restricts the flow of blood from the upper left chamber (left atrium) to the lower left chamber (left ventricle). Description In the heart, the valve that regulates the flow of...

  Definition Mitral valve prolapse (MVP) is a ballooning of the support structures of the mitral heart valve into the left upper collection chamber of the heart. Description Other names for MVP include floppy valve and Barlow's syndrome. The mitral valve is located on the left side of the heart between the top chamber (left atrium) and the...

Definition Mitral valve insufficiency is a term used when the valve between the upper left chamber of the heart (atrium) and the lower left chamber (ventricle) does not close well enough to prevent back flow of blood when the ventricle contracts. Mitral valve insufficiency is also known as mitral valve regurgitation or mitral valve incompetence. Description Normally,...

Definition A miscarriage is the loss of an embryo or fetus before the twentieth week of pregnancy. A pregnancy loss after the twentieth week is called a stillbirth. Description According to the December 1999 news release from the U.S. government's National Center for Health Statistics, about 16% of recognized pregnancies end in miscarriage (i.e., prior to 20 weeks' gestation)...

Definition Minoxidil is a drug available in two forms to treat different conditions. Oral minoxidil is used to treat high blood pressure and the topical solution form is used to treat hair loss and baldness. Purpose Minoxidil was the first drug approved by the FDA for the treatment of androgenetic alopecia (hair loss). Before that, minoxidil had been used as vasodilator...

Definition Minority health addresses the special medical and health needs associated with specific ethnic and other minority groups. Description The United States, along with many other countries, experiences cultural diversity. This fact poses health issues that are specific to ethnic and other minority groups. Additionally, the propensity for certain diseases or...

Definition The Minnesota Multiphasic Personality Inventory (MMPI-2; MMPI-A) is a written psychological assessment, or test, used to diagnose mental disorders. Purpose The MMPI is used to screen for personality and psychosocial disorders in adults and adolescents. It is also frequently administered as part of a neuropsychological test battery to evaluate cognitive...