Glossary

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M

Machado-Joseph disease:
Also known as spinocerebellar ataxia (SCA) type III, is probably the most common autosomal dominant SCA. This disorder was previously known as Azorean disease, as a large number of Portuguese families from the Azores Islands were found to be affected; however, SCA type III has now been reported in many other ethnic groups. In addition to unsteadiness of gait (ataxia), symptoms may involve parkinsonism, dystonia, and chorea. The affected protein is called ataxin-3; however, its function is not yet known.

Macrophages:
(1) Large cells of the immune system that has the ability to be phagocytic, that is, engulf and kill germs. This cell is also thought to be involved in plaque formation in arteries. (2) Immune cells that patrol the body for nonspecific invaders, engulfing them for destruction or for presentation to specialized immune cells.

Macular Degeneration:
The macula is the small area in the retina of the eye, 3 to 5 millimeters in size, that provides the sharpest and clearest vision. The macula can degenerate with the aging process, perhaps due to oxidation. The fatty acid DHA is present in large amounts in the retina.

Magnetic Resonance Imaging (MRI):
(1) A diagnostic scanning technique during which radio waves and an electromagnetic field are used to help create detailed, cross-sectional images of specific organs and tissues. MRI is often considered a particularly valuable imaging technique for studies of the brain and spinal cord because of the MRI’s ability to scan images from various angles and provide strong contrast between healthy and abnormal tissues. (2) A diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.

Maldigestion:
Impaired digestion, which can cause uncomfortable gastrointestinal symptoms and overall poor health.

MAO inhibitors:
MAO inhibitors are drugs that inhibit or prevent the action of an enzyme called monoamine oxidase (MAO). This enzyme helps to break down dopamine. When MAO is inhibited, the amount of time that dopamine acts in the brain is lengthened. Examples of MAO inhibitors that are used in the treatment of Parkinson disease include rasagiline, (Azilect®) and selegiline (Eldepryl®, Zelapar®).

Matched control subjects:
Matched control subjects are people who have similar characteristics, such as age, height, weight, education, sex, or other characteristics, as the patients being studied, but they do not have the disease. In this study, the control subjects were matched with regard to age and sex to each person who had PD. The control subjects did not have PD, parkinsonism, or any other form of tremor.

Mean:
An average; intermediate or middle position in value, quantity, or degree. The "arithmetic mean" is a statistical measure derived by adding a set of values and dividing the total by the number of values.

Mechanical pain:
Mechanical pain arises from pressure or touch.

Medicaid:
Government-funded healthcare coverage for US citizens who are not able to afford healthcare services.

Medicare:
Government-funded healthcare coverage for US citizens aged 65 years and older.

Melanoma:
Melanoma is the most serious life-threatening type of skin cancer. The tumor cells develop in the melanocytes, the cells that give skin its color.

Membrane:
A thin film that allows only some substances to pass through it or that prevents the mixing of two substances.

Membrane Lipid Peroxidation:
The oxidative deterioration of polyunsaturated fatty acids in which polyunsaturated fatty acids are converted to lipid hydroperoxides.

Meningitis:
An infection or inflammation of the meninges, the thin three-layer membranes that cover and protect the brain and spinal cord.

MERFF syndrome (myoclonus epilepsy with ragged-red fibers):
A rare hereditary disorder characterized by neurologic and muscle abnormalities due to defects of genetic material (DNA) in mitochondria, the rod-like structures outside the nuclei of cells that serve as a primary source of cellular energy. Removal and microscopic examination of minute samples of muscle fibers reveal structurally abnormal mitochondria (a finding known as "ragged-red fibers"). Associated symptoms include muscle weakness; sudden, involuntary, "shock-like" muscle contractions induced by voluntary movements or in response to external stimuli (action or reflex myoclonus); repeated seizures (epilepsy); progressively impaired coordination of voluntary movements (ataxia); and/or gradual deterioration of intellectual functioning (dementia). Some affected individuals may also have additional abnormalities, such as hearing loss; degeneration of the nerves (i.e., optic nerves) that convey impulses from the retinas to the brain (optic atrophy); short stature; heart muscle disease (cardiomyopathy); or other findings.

Metabolism:
(1) Refers to the ongoing chemical processes of cells of the body, including catabolism and anabolism. Catabolism or so-called "destructive metabolism" is the breakdown of complex chemical compounds into simpler substances, typically liberating or releasing energy. In contrast, anabolism or "constructive metabolism" refers to the "building up" or conversion of simple substances into more complex chemical compounds, requiring energy consumption (provided by catabolic processes). (2) The vast range of cellular and biochemical processes the body uses to create and convert the substances necessary for health and existence.

Methyl:
A molecule made of carbon and three hydrogen atoms. A methyl donor is any substance that can donate a methyl group to another molecule.

Methylphenidate:
A drug that is used as a central nervous system stimulant. A common trade name is Ritalin®. This drug is usually used to treat symptoms of attention-deficit/ hyperactivity disorder or narcolepsy. It acts like caffeine but has a more powerful alerting effect and is not as potent as amphetamines.

Metoclopramide:
A medication used to treat nausea and vomiting or migraine and to help with emptying the stomach for people with specific medical conditions. It works by blocking dopamine receptors.

Microbe:
A tiny living organism such as bacteria or yeast that has the potential to trigger chronic illness and disease.

Micrographia:
A change in handwriting with the script becoming smaller and more cramped.

Migraine:
A type of recurring headache that lasts for hours or days, is characterized by throbbing or pulsing pain, worsens with physical activity, and is usually confined to one side of the head, although not always on the same side. The pain is usually accompanied by sensitivity to light and by nausea or even vomiting.

Mini-Mental State Examination:
This short clinician-administered test measures cognitive status (the ability to think, calculate, and reason) in adults. This test is used to measure the presence of impaired cognition or a change in cognition over time.

Mirapex:
Medication to treat parkinsonian symptoms. Useful in managing "on/off" phenomenon and "wearing off" effect. Less dytonic reactions and may preserve neuronal function while allowing for lower doses of levodopa therapy. Side-effects are: hypotension, constipation, dizziness, drowsiness, nightmares, psychosis, skin rash, incontinence, nasal congestion, visual disturbances, insomnia, headache, hallucinations, among others.

Mitochondria:
(1) Referring to mitochondria or rod-like structures inside cells of the body whose primary functions include the production and regulation of energy. (2) The chemical factories of cells, where energy is made. Thousands of mitochondria are present in each cell.

Mitochondrial dysfunction:
Mitochondria are the main energy source of cells. Mitochondria convert nutrients into energy and also perform many other specialized tasks. Dysfunction means that something is not working or functioning in the correct way. Therefore, mitochondrial dysfunction refers to a situation in which the mitochondria are not working properly.

Molecule:
The smallest possible combination of atoms that retains the chemical properties of the substance. For instance, a molecule of water consist of three atoms - two are hydrogen and one is oxygen.

Monoamine:
A molecule containing one amine group. An amine is an organic compound containing nitrogen. The so-called "biogenic monoamines" are natural, biologically active compounds that often function as neurotransmitters, including dopamine, serotonin, noradrenaline, and epinephrine.
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Monoamine Oxidase (MAO):
An enzyme that breaks down dopamine, norepinephrine, and epinephrine in synapses. Two types are present, types A and B. Certain drugs can inhibit the action of MAOs; these drugs are called MAO inhibitors. There are two types of MAO "A" and "B." In Parkinson's disease, it is beneficial to block the activity of MAO B.

Monotherapy:
A drug used alone to treat a disease (opposite of combination therapy).

Mood or bipolar disorder:
Mood or bipolar disorder is a mental illness in which people have wide mood swings. The moods include mania, during which the person has lots of energy or is excessively irritable, and depression, during which the person feels sad and hopeless. The person with bipolar can have normal moods between the swings but may also switch quickly between the highs and lows. Psychosis: Psychosis is a thought disorder characterized by impaired ability to distinguish reality from unreality, personality changes, and deterioration of normal social functioning. People with psychosis may experience hallucinations, illusions, or delusions, or they may be paranoid or have distorted thinking.

Motor fluctuations:
Motor fluctuations occur when levodopa is used to treat Parkinson’s disease. As the disease becomes worse, the number of cells in the brain that store dopamine decreases, the symptoms of Parkinson’s disease worsen, and levodopa is not as effective in controlling the symptoms. When this happens, a person is said to have “off” episodes.

Motor symptoms:
The motor symptoms of Parkinson's disease include tremor, stiffness (called rigidity), slowness or absence of movement (called bradykinesia or akinesia, respectively), and difficulty maintaining balance or unstable posture.

MPTP:
A toxic chemical, exposure to which can lead to Parkinson's.

Multiple Sclerosis (MS):
A progressive disease of the central nervous system characterized by destruction of myelin (demyelination), the fatty substance that forms a protective sheath around certain long nerve fibers (axons). Myelin serves as an electrical insulator, enabling the effective transmission of nerve signals. Patients with MS may develop paresthesias, such as numbness or tingling; muscle weakness and stiffness; impaired coordination; abnormal reflexes; an inability to control urination (urinary incontinence); slurred speech; visual disturbances; and/or other symptoms and findings.

Multiple Sleep Latency Test (MSLT):
The MSLT is used to measure how likely a person is to fall asleep. The test takes place over a seven-hour period during the day. Every two hours, for 20 minutes, the patient lies in a quiet dark room and is hooked up to a machine that measures brain waves, heart rate, muscle activity, and eye movements. This recording allows the doctor to see how quickly the patient falls asleep in this situation or if the patient falls asleep at all.

Multiple System Atrophy:
A neurodegenerative disorder characterized by parkinsonism, ataxia, and dysfunction of the autonomic nervous system.

Muscle Tone:
The low level of contraction in a muscle not being intentionally contracted.

Muscular Dystrophy:
The name given to a group of diseases that are, for the most part, genetically determined and cause gradual wasting of muscle with accompanying weakness and deformity.

Mutation:
A change in a gene, such as loss, gain, or substitution of genetic material, that alters its function or expression. This change is passed along with subsequent divisions of the affected cell. Gene mutations may occur randomly for unknown reasons or may be inherited.

Myelin:
The whitish, fatty substance forming the segmented, multilayered wrappings or "sheaths" around certain long nerve fibers or axons. Myelin sheaths electrically insulate axons, serving to speed the transmission of nerve signals (action potentials).

Myelinated:
Referring to long nerve fibers (axons) that have myelin sheaths. Consisting of segmented, multilayered wrappings of myelin, a whitish protein, myelin sheaths wrap around certain nerve fibers, providing electrical insulation and serving to speed the transmission of nerve signals.

Myelogram:
A procedure that uses dye injected into the spinal canal to make the structure clearly visible on x-rays.

Myoclonic:
Pertaining to myoclonus or irregular, involuntary, shock-like contractions or spasms of a muscle or muscle group.

Myoclonus:
A neurologic movement disorder characterized by brief, involuntary, twitching or "shock-like" contractions of a muscle or muscle group. These jerk-like movements may be accompanied by periodic, unexpected interruptions in voluntary muscle contraction, leading to lapses of sustained posture (known as "negative myoclonus"). So-called "positive" and "negative" myoclonus are often seen in the same individuals and may affect the same muscle groups. Myoclonus is often a nonspecific finding, meaning that it may occur in the setting of additional neurologic abnormalities and be associated with any number of underlying conditions or disorders. In other patients, myoclonus appears as an isolated or a primary finding. Depending on the underlying cause and other factors, the shock-like muscle jerks may occur repeatedly or infrequently; may tend to appear under specific circumstances (e.g., with voluntary movements or in response to specific external sensory stimuli); and may affect any body region or regions.

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Document last modified:06/06/08 12:26:53 AM