Glossary

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A

Ablation:
Surgical destruction or removal of tissue, an organ, or a precise region of a particular structure. Ablation may involve surgical cutting (excision); chemical destruction, such as injection of phenol; or the use of high frequency electrical current or radio waves. For example, pallidotomy is a procedure used in the treatment of Parkinson's disease or certain other movement disorders. The procedure involves surgical ablation of part of the internal portion of the globus pallidus (GPi)--i.e., a brain region involved in regulating movement--in an attempt to "rebalance" movement and posture control. Once a wire probe is inserted into and precisely positioned within the GPi, it heats and destroys adjacent tissue through the emission of radio waves.

Accelometer:
A device used to measure the rate of change in velocity over a specific period of time. Measures the rate or "speed" ot the tremor cycle.

Acetic acid:
CH3COOH; a sour, colorless liquid found in vinegar.

Acetyl:
CH3CO; a two carbon acetic acid molecule from which a hydroxyl group (OH) has been removed.

Acetyl-coenzyme A (Acetyl-CoA):
A condensation product of acetic acid and coenzyme A. It is an intermediate in the transfer of two-carbon molecules in the metabolism of sugars and fatty acids.

Acetylcholine:
(1) A chemical formed by choline and an acetyl group. It is a neurotransmitter in the nervous system used to transmit nerve impulses. Acetylcholine slows down heart rate, dilates blood vessels, and increases activity of the gastrointestinal system. In the brain, acetylcholine is involved with learning and memory. (2) A chemical messenger released by cholinergic nerves. Normally in many parts of the body, including the brain, and necessary to normal body functioning. There appears to be a reciprocal seesaw relationship between acetylcholine and dopamine and their respective nerve cell systems. (3) Chemical in the body of animals that functions as a neurotransmitter, sending electrical impulses across synapses between nerve cells, and from motor neurons to muscle cells, causing the muscle cells to contract. As an electric impulse reaches the nerve ending, the nerve cell releases acetylcholine, which passes across the synapse and bonds chemically with a receptor molecule in the membrane of the neighboring nerve cell. The bonding of acetylcholine to the receptor molecule alters the polarity and permeability of the membrane so that the nerve impulse can be transmitted. The effect of acetylcholine can be neutralized by an enzyme, such as cholinesterase, which decomposes acetylcholine through the process of hydrolysis. When acetylcholine is decomposed, the muscle relaxes. (4) A chemical in the brain that acts as a neurotransmitter. (5) A neurotransmitter present at junctions of nerve and muscle cells and various sites of the central nervous system, including the cerebral cortex and the basal ganglia. Primary functions of acetylcholine include regulating the delivery of messages from neurons to skeletal muscle fibers, smooth (involuntary) muscle fibers, and effector organs as well as between nerve cells in the brain and spinal cord. Acetylcholine also functions as a vasodilator and triggers certain actions within the parasympathetic nervous system, such as lowering blood pressure and slowing heart and breathing rates.

Acetylcholinesterase:
The enzyme that breaks down acetylcholine into choline and acetate or acetic acid. It is located in the synaptic cleft.

Acetylation:
The formation of an acetyl derivative.

Action tremor:
(1) A tremor that occurs during the performance of voluntary movements. Such tremors include postural, isometric, kinetic, and intention tremors. (2) Rhythmic, involuntary movement of a limb when movement is initiated, e.g., when writing or lifting a cup. Not usually seen in the earlier stages of Parkinson's.

ACTH (Adrenocorticotrophic hormone):
A hormone secreted by the pituitary gland. It stimulates the adrenal gland to make steroids, particularly cortisol. ACTH is released in response to stress, leading to high cortisol levels.

Activities of daily living (ADL):
(1) Functions that are typically performed as part of a person's daily routine, such as dressing, bathing, eating, toileting, leisure activities, socialization, and other functions of daily living. (2) Personal care activities necessary for everyday living, such as eating, bathing, grooming, dressing, and toileting; a term often used by healthcare professionals to assess the need and/or type of care a person may require.

Acute:
Short duration of effect. It often refers to symptoms, which can appear or resolve suddenly.

Adaptive/Assistive Equipment:
Special device which assists in the performance of self-care, work or play/leisure activities or physical exercise.

Adaptive immunity:
Involves cells that respond to specific antigens. T cells, B cells, and antibodies are part of adaptive immunity.

ADD (Attention deficit disorder):
A common neurological condition in children characterized by learning difficulties and poor attention.

Adenosine triphosphate (ATP):
ATP is the molecule that provides the energy in the cells of all living things.

Adipose cells:
The scientific term for cells that contain the body's fat stores.

ADHD (Attention deficit hyperactivity disorder):
Similar to ADD; children with ADHD additionally suffer with poor impulse control and hyperactive behavior.

Adherence to therapy:
Taking medications in the prescribed dose and at the correct time.

Adrenal glands:
A pair of small, pyramid-shaped glands located on the top of each kidney, which produce important "stress" hormones such as cortisol, DHEA-S, and adrenaline.

Adrenaline (Epinephrine):
The neurotransmitter of the adrenal gland which is secreted in moments of crisis. It stimulates the heart to beat faster and work harder, increases the flow of blood to the muscles, causes an increased alertness of mind, a nd produces other changes to prepare the body to meet an emergency.

Adrenocortex:
The outer yellowish region of the adrenal gland that secretes many important steroid hormones, including DHEA-S.

Adult day care:
Adult day care is a community program for disabled adults. In this safe setting, people can socialize, participate in activities and get health care. Day care centers are open during business hours on weekdays. Some programs also run during the evenings and on weekends.

Advance directives:
Documents (such as a Living Will) completed and signed by a person who is legally competent to explain his or her wishes for medical care should he or she become unable to make or communicate. Advance directives include living wills which state your wishes about medical treatments at the end of life or health-care powers of attorney which lets you choose someone to make medical decisions for you.

Adverse event:
According to the United States Food and Drug Administration, an adverse event is any undesirable experience associated with the use of a medical product in a patient. The event is serious and should be reported when the patient outcome is death or is life-threatening; results in hospitalization, disability, or congenital anomaly; or requires intervention to prevent permanent impairment or damage.

Affective disorders:
Psychological conditions involving mood, such as depression and bipolar disorder.

Age-Related cognitive decline (ARCD):
The gradual loss of mental abilities with age.

Agitation:
A non-specific symptom of one or more physical, or psychological processes in which vocal or motor behavior (screaming, shouting, complaining, moaning, cursing, pacing, fidgeting, wandering) pose risk or discomfort, become disruptive or unsafe, or interfere with the delivery of care in a particular environment.

Agonist:
(1) A drug or compound capable of attaching to a receptor and initiating a reaction. Compare with antagonist. (2) A substance responsible for triggering a response in a cell, such as a hormone, neurotransmitter, etc; a prime mover or muscle directly responsible for a change in position of a part. (3)A muscle whose contraction executes an intended movement.

Akathisia:
A neurologic condition of motor restlessness, manifested by a sensation of muscular quivering, an urge to constantly move about, and an inability to sit still.

Akinesia:
(1) Absence of movement or loss of the ability to move such as temporary or prolonged paralysis or "freezing in place." (2) The inability to move, also called freezing. It can occur in people with Parkinson’s disease.

Akinetic:
Referring to absence or poverty of voluntary movement; loss of the ability to move all or part of the body.

Alkaloid:
Any of hundreds of compounds found in plants with a nitrogen atom connected to two carbon atoms, and often formed in a ring structure. Many commonly known chemicals and drugs are alkaloids, including nicotine, cocaine, quinine, morphine, and ephedrine.

Alpha linolenic acid (ALA):
The primary member of the Omega-3 family of essential fatty acids. The body converts ALA into either docosahexaenoic acid or eicosapentaenoic acid. ALA is found in high quantities in flaxseed oil.

Alpha-synucleinopathy:
A group of neurologic diseases that are associated with abnormal alpha-synuclein proteins. They include Multiple System Atrophy, Lewy body disease, Parkinson disease, Progressive Supranuclear Palsy (also a tauopathy), and Pantothenate Kinase–associated Neurodegeneration (PKAN) or Pantothenate Kinase 2 (PANK2) deficiency (previously called Hallervorden-Spatz disease). The morphology and array of components that are immunoreactive to anti–alpha-synuclein antibodies in persons with these diseases differ from those found in persons with Multiple System Atrophy.

Alpha-tocopherol:
Chemical name for biologically active form of Vitamin E.

Alpha 2-adrenergic agonist:
A drug that reduces the activity of the neurotransmitter norepinephrine by stimulating certain receptors within the central nervous system (central presynaptic alpha 2-adrenergic receptors). The release of norepinephrine triggers action within the sympathetic nervous system. This part of the nervous system regulates certain involuntary activities during stress, such as increasing the heart rate, deepening breathing, and raising blood pressure. Norepinephrine also plays a role in regulating mood and emotion. The administration of alpha 2-adrenergic agonists may result in a reduced heart rate and lowered blood pressure and have depressive or sedative effects.

Alzheimer's disease:
(1) A form of degenerative brain disease resulting in progressive mental deterioration with disorientation, memory disturbance, and confusion and leading to progressive dementia often accompanied by dysphasia and/or dyspraxia. The condition may also give rise ultimately to spastic weakness and paralysis of the limbs, epilepsy, and other variable neurological signs. (2) A progressive brain disease leading to memory loss, interference with thinking abilities, and other losses of mental powers. Brain cells show degenerative damage. Neurons that use the neurotransmitter acetylcholine are most affected. (3) A condition where the brain develops abnormal protein deposits and tissues, which leads to problems with memory and thought processes.

Amantadine:
A drug normally used to treat Parkinson diseases which stimulates the release of available dopamine in the brain. It may be used by itself or used along with levadopa.

Ambulant (ambulatory):
Able to walk; may be used to describe patients who do not require a wheelchair or are not confined to bed.

Americans With Disabilities Act:
US law that prohibits discrimination against people with disabilities and requires reasonable accommodations for them. This applies to the fields of employment, government, and public and commercial facilities.

Amino acid:
(1) The chemical "building blocks" or basic structural units of proteins. All proteins in the body are formed from a "pool" of 20 different amino acids. Some are essential amino acids and must be supplied by the diet. The remainder are classified as "nonessential." These can be made by the body and need not come from the diet. (2) The primary chemical building blocks the body uses to produce protein. A deficiency of even a single amino acid can impair the body's production of many proteins, and result in hormone imbalances, breakdown of muscle tissue, and weakened immune function.

Ambulation:
The act of walking.

Amniocentesis:
A screening or diagnostic procedure during which a sample of amniotic fluid surrounding the developing fetus is withdrawn by means of an ultrasound-guided needle. The amniotic sac is a fluid-filled membrane that surrounds and protects the developing fetus within the uterus. Amniotic fluid contains cells that may be used for DNA analysis, chromosomal testing, and enzyme studies. Such testing may detect certain genetic disorders, metabolic diseases, chromosomal abnormalities, or developmental defects. This procedure is typically performed between the 14th and 18th week of pregnancy.

Amplitude:
The "size" or "height" of a tremor; the extend or breadth of a tremor's range.

Amyloid:
Any of a group of proteins that deposit in the braln and cause amyloidosis. Amyloidosis is often associated with Alzheimer's disease.

Amyotrophic lateral sclerosis (ALS):
A terminal neurological disorder characterized by progressive degeneration of motor cells in the spinal cord and brain. It is often referred to as "Lou Gehrig's disease."

Anabolic:
The building up of proteins from simpler molecules in the body, (such as proteins forming from amino acids). This generative process results in increased lean muscle mass, stronger bones, and a greater energy supply. Anabolic hormones include DHEA-S, testosterone, and growth hormone.

Analgesic:
A drug that reduces or takes away pain.

Analog (Analogue):
(1) A chemical compound or agent that is similar to another in structure yet differs concerning a particular element; it may have a similar or different mode of action. (2) A tissue, organ, or other bodily structure that has the same function or organization as another yet has a different evolutionary origin.

Androgen:
A hormone that encourages the development of male sexual characteristics. Some of the androgens made by the adrenal glands are DHEA, androstenedione, and testosterone.

Angina pectoris:
Acute chest pain caused by spasms that squeeze the coronary arteries.

Anosmia:
The lack of sense of smell. People who have complete anosmia are not able to detect any odors. People who have partial anosmia are not able to detect one or more odors.

Antagonist:
(1) A drug or compound that interferes with the action of, or counteracts the action of, another drug or group of drugs. (2) A drug that blocks a receptor, preventing stimulation. (3) A muscle whose contraction opposes an intended movement.

Antibodies:
(1) Specialized proteins that function as an essential part of the immune system. Antibodies are produced by certain white blood cells (B cells) in response to the presence of specific, usually foreign proteins (i.e., antigens), helping the body to neutralize and destroy the invading microorganism, foreign tissue cell, or other antigen in question. (2) The proteins produced by B cells in response to an infection or vaccine. Also called immunoglobulins, antibodies bind to specific antigens.

Anticholinergic:
Acetylcholine is one of the body's many neurotransmitters. A neurotransmitter is a chemical substance that nerve cells use to communicate with each other, with muscles, and with many glands. Drugs that block the action of the neurotransmitter acetylcholine are said to have anticholinergic effects. Most of these drugs aren't designed to block acetylcholine; their anticholinergic effects are side effects.

Anticholinergic agents:
Anticholinergic medications are drugs that block the action of acetylcholine, a neurotransmitter with an effect opposite to that of dopamine. By blocking the action of acetylcholine, these drugs increase the ability of dopamine to control movement. Examples of anticholinergic drugs used in the treatment of Parkinson disease include trihexyphenidyl (Artane®), benztropine (Cogentin®), and ethopropazine (Parsidol®).

Anticholinergic effects:
Elderly people are particularly sensitive to drugs with anticholinergic effects because the amount of acetylcholine in the body decreases with age and because their bodies are less able to use what's there. Drugs that have anticholinergic effects can cause confusion, blurred vision, constipation, dry mouth, light-headedness, and difficulty with urination or loss of bladder control.

Anticholinergics:
Drugs that block the action of acetylcholine, a neurotransmitter whose effects oppose dopamine. By blocking acetylcholine's action, these medications increase dopamine's ability to control movement.

Anticholinergic Parkinson's drugs (Artane, Cogentin):
The group of drugs which decreases the action of acetylcholine. The specified drugs may help reduce rigidity, tremor, and drooling in Parkinson's.

Anticholinesterase:
An agent that inhibits action of acetylcholinesterase (AChE). AChE is an enzyme that inactivates acetylcholine, a neurotransmitter at the junctions of nerve and muscle cells (neuromuscular junctions) that regulates the delivery of messages from neurons to muscle fibers. By inhibiting the activity of AChE, such medications allow high levels of acetylcholine to accumulate, potentially enabling repeated stimulation of nerves at neuromuscular junctions.

Anticoagulent:
A drug used to prevent blood clot formation.

Anticonvulsant Medication:
An agent that prevents or arrests convulsive seizures.

Antidepressant:
A medication used to treat depression.

Antiemetic:
A drug used to prevent or reduce nausea or vomiting.

Antigen:
(1) Any substance that may trigger a particular immune response, such as the production of antibodies. Antigens may be foreign proteins of invading microorganisms (e.g., viruses, bacteria), toxins, or foreign tissue cells (e.g., used in transplantation). (2) The term for a substance or molecule recognized by the immune system—either from a pathogen such as a virus or, in error, from the body’s own cells (“self”). In MS, the myelin that surrounds nerves is mistaken as an antigen.

Antihistamine:
A drug that counters the effects of histamine, a compound that causes dilatation of capillaries, contraction of smooth muscle, and stimulation of gastric acid secretion and that is released during allergic reactions. commonly used to treat allergies. Used in the past for Parkinson's as they sometimes had beneficial effects on symptoms due to their anticholinergic properties.

Antinutrient:
A substance, such as white flour, refined sugar, or trans-fatty acid, that hinders the actions of nutrients. The modern diet contains a high amount of antinutrients.

Antioxidant:
(1) A substance that combines with damaging molecules, neutralizes them, and thus prevents the deterioration of DNA, RNA, lipids, and proteins. Vitamins C, E, selenium and beta-carotene are the best-known antioxidants, but more and more are being discovered each year. (2) Agents that inhibit or neutralize potentially harmful compounds known as free radicals. Free radicals are produced during metabolic activity. High levels of free radicals may eventually lead to impaired functioning and destruction of neurons and other bodily cells. Certain antioxidants are thought to neutralize free radicals before cellular damage occurs. (3) Any of a large group of substances whose presence slows down the deterioration of fatty acids caused by oxygen and other substances.

Aorta:
The main artery of the body. The aorta receives oxygen-rich (oxygenated) blood from the lower left chamber (ventricle) of the heart for distribution to most arteries of the body, with the exception of the pulmonary artery, which distributes oxygen-deficient (deoxygenated) blood from the lower right ventricle to the lungs.

Aphasia:
Loss of the ability to express oneself and/or to understand language. Caused by damage to brain cells rather than deficits in speech or hearing organs.

Apnea:
A temporary stoppage of breathing.

Apomorphine:
A derivative of morphine and a dopamine agonist. Currently experimentally used as injectable treatment for severe Parkinson's.

Apoptosis:
Cell death due to a programmed pattern of gene expression; a form of cell death in which certain enzymes activate to degrade DNA within the nucleus, resulting in cellular degeneration and loss.

Apraxia:
Loss of the ability to sequence, coordinate, and execute certain purposeful movements and gestures in the absence of motor weakness, paralysis, or sensory impairments. Apraxia is thought to result from damage to the cerebral cortex, such as due to stroke, brain tumors, head injury, or infection. It may also occur as a result of impaired development of the cortex as in certain neurodevelopmental disorders, including Rett syndrome. Apraxia may affect almost any voluntary movements, including those required for proper eye gaze, walking, speaking, or writing.

Arachidonic acid (ARA):
A member of the Omega-6 family of essential fatty acids. The body makes ARA from the primary Omega-6, linoleic acid.

ARCD:
See Age-related cognitive decline.

Archimedes spirals:
A relatively simple test used to evaluate tremor severity. During this test, the patient is asked to draw increasingly wider circles on a piece of paper.

Arrhythmias:
(1) Variations in the normal heartbeat. (2) A disturbance of the heartbeat. An arrhythmia can be fatal, and can occur in persons with no history of cardiovascular disease.Maribel

Arteriogram (Also called angiogram):
A procedure that provides a scan of arteries going to and through the brain.

Arthocentesis:
The removal of joint fluid.

Arthroscopy:
Examination of the inside of a joint by using a thin optical instrument.

Aspiration:
A condition when fluid of food enters the lungs through the wind pipe. Aspiration can cause a lung infection or pneumonia.

Assessment:
An assessment of mental status is a test of a person's ability to think, feel and react to others. A doctor usually performs a mental status assessment.

Assistive devices:
Tools designed or adapted to help people perform a particular task, such as walking, buttoning a shirt, or picking up food.

Asterixis:
Involuntary, jerking or flapping movements, especially of the hands. Extending the patient's arm with the wrist bend in a backward position may induce this form of tremor, which may be associated with advanced liver disease.

Astrocyte:
A type of glial cell. Glial cells are the connective tissue cells of the central nervous system (CNS), serving as the supportive structure that holds together and protects neurons. Astrocytes are relatively large glial cells with thread-like projections that connect with neurons and small blood vessels (capillaries). These projections form part of the so-called "blood-brain barrier." This barrier slows or prevents the passage of unwanted substances, such as harmful chemicals, infectious agents, etc., from the bloodstream into the brain. Astrocytes also accumulate in areas where nerves have been damaged (astrocytosis), sealing off these areas. An excess of astrocytes in damaged areas of the CNS is known as gliosis.

Ataxia:
(1) Ataxia is a symptom, not a specific disease or diagnosis. Ataxia means clumsiness, or loss of coordination. Ataxia may affect the fingers and hands, the arms or legs, the body, speech or eye movements. This loss of coordination may be caused by a number of different medical or neurologic conditions; for this reason, it is important that a person with ataxia seek medical attention to determine the underlying cause of the symptom and to get the appropriate treatment. (2) A condition characterized by an impaired ability to coordinate voluntary movements. Ataxia may result from damage to the cerebellum, cerebellar pathways, or the spinal cord due to various underlying disorders, conditions, or other factors. These may include infection, head injury, stroke, brain tumors, neurodegenerative disorders, alcohol or drug intoxication, or certain hereditary diseases (e.g., Friedreich's ataxia, ataxia-telangiectasia). Associated symptoms may vary, depending upon the site of damage within the central nervous system. However, the condition is often characterized by incoordination, postural imbalance, and a lurching, unsteady manner of walking (gait). Additional findings may include slurred speech (dysarthria); rapid, involuntary, rhythmic eye movements (nystagmus); and/or other abnormalities. There are at least four vitamin/mineral defiencies that may cause ataxia symptoms - these are Vitamins B1, B12, E and Zinc. Those with ataxia symptoms should check for problems involving these nutrients.

Ataxia-telangiectasia (AT):
A hereditary, progressive disorder that typically becomes apparent in early childhood and is characterized by increasing neurodegenerative changes of the cerebellum, a brain region involved in producing coordinated voluntary movements, sustaining balance, and maintaining proper posture. Associated symptoms typically include delayed motor development; an unsteady, awkward manner of walking; drooling; impaired articulation of speech (dysarthria); dependence on thrusts of the head to achieve proper focusing of the eyes; and involuntary, rapid, jerky eye movements (nystagmus). Affected children may also develop involuntary, "shock-like" muscle spasms (myoclonus); sustained muscle contractions that result in repetitive twisting motions or unusual postures or positions (dystonia); or irregular, jerky, relatively rapid involuntary movements (chorea). AT is also typically associated with permanent widening (dilation) of groups of blood vessels (telangiectasias), particularly in sun-exposed skin regions of the face and the transparent membranes covering the whites of the eyes. In addition, AT is characterized by deficient functioning of the immune system (immunodeficiency), leading to recurrent respiratory and skin infections and an increased risk of certain malignancies (e.g., certain leukemias or lymphomas). The disorder, which is transmitted as an autosomal recessive trait, is thought to result from defective repair of DNA.

Atherosclerosis:
A condition in which the arteries in the heart and other parts of the body accumulate plaque and become narrow, decreasing the flow of blood and increasing the risk for a clot; it's also known as "hardening of the arteries." Atherosclerosis can lead to a heart attack or stroke if the affected artery becomes completely blocked.

Athetosis:
Involuntary, relatively slow, writhing movements that essentially flow into one another. Athetosis is often associated with chorea, a related condition characterized by involuntary, rapid, irregular, jerky movements. Although athetosis may be most prominent in the face, neck, tongue, and hands, the condition may affect any muscle group. Athetosis may occur in association with certain neurodegenerative diseases, such as Huntington's or Wilson's disease, or cerebral palsy (CP). It may also result from infections affecting the brain or the use of particular medications.

Atom:
The ultimate, indivisible, and smallest particle of an element. For instance, hydrogen and oxygen are atoms. When two hydrogen atoms and one oxygen atom get together, they form a molecule of water.

ATP (Adenosine Triphosphate):
The primary energy currency of a cell, derived from the metabolism of glucose, amino acids, and fatty acids.

Atropy:
Wasting away or loss of a cell, tissue, or organ due to disease, malnutrition, insufficient blood supply, or other causes, such as loss of skeletal muscle mass due to peripheral nerve damage.

Attention-deficit/hyperactivity disorder:
A diagnosis applied to children and adults who consistently display certain characteristic behaviors over a period of time. The most common behaviors fall into three categories: inattention, hyperactivity, and impulsivity.

Attorney (elder law):
An elder law attorney handles general estate planning issues and counsels clients about planning for the future with alternative decision-making documents. The attorney can also assist the client in planning for possible long-term care needs, including nursing home care. Not all attorneys specialize in elder law. Your local bar association or the National Academy of Elder Law Attorneys and your local chapter can refer you to elder law attorneys in your area.

Atypical:
Irregular; not standard or characteristic; not conforming to type.

Atypical neuroleptics:
Antipsychotic drugs that cause less parkinsonian side effects than older treatments for psychosis.

Atypical parkinsonism:
Disease that displays the symptoms commomly associated with Parkinson's Disease but does not respond to dopaminergic or other therapies that are normally used to treat Parkinson's. The 2 most common of these conditions are multiple system atrophy and progressive supranuclear palsy. Sometimes in early disease there is some drug responsiveness, but it is not dramatic and never long-standing. There is no effective therapy to treat rigidity commomly associated with these diseases. Other drugs, such as muscle relaxants, are of no or minimal value. Only supportive care is available for these patients. Also known as Parkinson-plus syndrome or syndromes.

Auditory:
Pertaining to the sense of hearing or the organs involved in hearing.

Augmentation:
A phenomenon that may occur as a result of the use of certain medications (particularly levodopa). Augmentation is characterized by the emergence of worsening symptoms earlier in the day (e.g., early evening, afternoon, or morning). Many people who take levodopa and some who take other dopamingeric agents develop augmentation, especially those who have severe symptoms or are taking high doses of the drug.

Augmentation and alternative communication:
Use of forms of communication other than speaking, such as sign language, "yes/no" signals, gestures, picture board, and computerized speech systems to compensate (either temporarily or permanently) for severe expressive communication disorders.

Aura:
A sensory disturbance that may precede a neurological episode, such as a migraine; also called a prodrome. It may consist of visual disturbances or hallucinatory sounds, odors, tastes, or touch sensations.

Autoimmune:
Referring to an immune response against one's own tissues or organs. Autoimmune diseases result from abnormal immune reactions in which the actions of certain white blood cells (T cells) are directed against "self proteins" (autoantigens) or normal tissue components (i.e., cell-mediated immune response)--or in which specialized proteins (antibodies) produced in response to specific, usually foreign proteins (antigens) improperly act against certain of the body's own cells (i.e., antibody-mediated immune response). In certain disorders, the autoimmune process may be primarily directed against one organ, such as the thyroid gland in Hashimoto's thyroiditis or the pancreas in insulin-dependent diabetes mellitus, or may involve multiple organs and bodily systems.

Autoimmune disease:
A disease that results from the body’s reaction to itself, instead of to infection. Examples include lupus, multiple sclerosis, and rheumatoid arthritis.

Automatic behavior:
Automatic behaviors are those during which a person performs a routine task without any awareness of doing so.

Autonomic:
The autonomic nervous system controls most of the involuntary reflexive activities of the human body. The system is constantly working to regulate the glands and many of the muscles of the body through the release or uptake of the neurotransmitters acetylcholine and norepinephrine. The autonomic nervous system is made up of two primary parts: the sympathetic and parasympathetic systems. The sympathetic nervous system prepares the body for emergencies or times of stress and is responsible for the body's "fight or flight" response when faced with a dangerous situation. During this response, the heart rate and blood pressure increase, the pupils of the eye dilate, and the digestive system slows down. The parasympathetic system helps the body's functions return to normal after they have been stimulated by the sympathetic nervous system and also has some responsibility for keeping the body's immune system properly functioning.

Autonomic dysregulation:
Malfunctioning of the autonomic nervous system, the portion of the nervous system that conveys impulses between the blood vessels, heart, and all the organs in the chest, abdomen, and pelvis and the brain (mainly the medulla, pons and hypothalamus)

Autonomic nervous system:
(1) The branch of the nervous system that controls internal organs in the body, i.e., heart, lungs. (2) A part of the nervous system responsible for control of bodily functions that are not consciously directed; for example, heart rate, blood pressure, sweating, intestinal movements, temperature control.

Autosomal dominant trait:
Human traits, including an individual's eye color, hair color, or expression of certain diseases, result from the interaction of one gene inherited from the father and one gene from the mother. In autosomal dominant disorders, the presence of a single copy of a mutated gene may result in the disease. In other words, the mutated gene may dominate or "override" the instructions of the normal gene on the other chromosome, potentially leading to disease expression. Individuals with an autosomal dominant disease trait have a 50 percent risk of transmitting the mutated gene to their children.

Autosomal recessive trait:
With autosomal recessive disorders, two copies of the disease gene must be inherited in order for an individual to potentially develop the disease. If both the mother and father carry a copy of the disease gene, each child has a 25 percent risk of inheriting the two genes for the disease. There is a 50 percent risk that their children may inherit one copy of the disease gene and be carriers for the disease trait (heterozygous carriers). In addition, there is a 25 percent chance that the parents' offspring will inherit two normal copies of the gene and will not develop the disorder nor be carriers for this disease trait.

Axons:
Nerve fibers. (1) Axons are the relatively slender extensions of neurons that transmit nerve impulses away from nerve cell bodies. The ends of the axons or "terminals" release chemical substances known as neurotransmitters, enabling the transmission of nerve impulses to other neurons or effector organs. The whitish, fatty, protein-containing substance called myelin forms an insulating, protective, cylindrical sheath around some axons, serving to increase the speed and efficiency of nerve impulse transmissions. (2) The long, slender part of a nerve cell (or neuron) that transmits impulses from the body of the nerve. Axonal damage caused by MS is now known to occur early in the disease process, along with loss of the myelin covering of the axon.

Ayurveda:
A traditional system of medicine practiced in India since the first century A.D. Ayurvedic practitioners combine herbs, oils, and other natural systems in treating diseases. Many herbs used in Ayurvedic medicine are now gaining popularity in Western countries.

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