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Glossary - Nervous System Disorders

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acetylcholine - a chemical in the brain that acts as a neurotransmitter.

action tremor - a tremor that increases when the hand is moving voluntarily.

activities of daily living (ADLs) - 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.

advance directives - documents (such as a Living Will) completed and signed by a person who is legally competent to explain his/her wishes for medical care should he/she become unable to make those decisions at a later time.

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 - a drug that increases neurotransmitter activity by stimulating the receptors of a neurotransmitter directly.

akinesia - no movement.

Alzheimer's disease - A progressive, degenerative disease that occurs in the brain and results in impaired memory, thinking, and behavior.

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."

arteriogram (also called angiogram) - a procedure that provides a scan of arteries and/or veins going to and through the brain.

ataxia - loss of balance.

athetosis - slow, involuntary movements of the hands and feet.

atrophy - wasting, shrinkage of muscle tissue or nerve tissue.

axon - the long, hair-like extension of a nerve cell that carries a message to the next nerve cell.


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basal ganglia - several large clusters of nerve cells, including the putamen and globus pallidus, deep in the brain below the cerebral hemispheres.

Bell's palsy - An unexplained episode of facial muscle weakness or paralysis that begins suddenly and steadily worsens.

blink rate - the number of times per minute that the eyelid automatically closes - normally 10 to 20 per minute.

blood-brain barrier - the protective membrane that separates circulating blood from brain cells.

bradykinesia - slowness of movement.

bradyphrenia - slowness of thought processes.

brain attack (also called stroke) - happens when brain cells die because of inadequate blood flow to the brain or when function of a part of the brain is suddenly lost because of the rupture of a blood vessel in the brain.


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central nervous system - the brain and the spinal cord.

cerebellum - a large structure consisting of two halves (hemispheres) located in the lower part of the brain; responsible for the coordination of movement and balance.

cerebral embolism - a brain attack that occurs when a blood clot (embolus) or some other particle forms in a blood vessel and travels to a blood vessel in the brain to the point where it blocks blood flow in the vessel; often the clot forms away from the brain, usually in the heart.

cerebral hemorrhage - a type of stroke occurs when a defective artery in the brain bursts, flooding the surrounding tissue with blood.

cerebral spinal fluid analysis (also called spinal tap or lumbar puncture) - a procedure used to make an evaluation or diagnosis by examining the fluid withdrawn from the spinal column.

cerebral thrombosis - the most common type of brain attack; occurs when a blood clot (thrombus) forms and blocks blood flow in an artery bringing blood to part of the brain.

cerebrum - consists of two parts (lobes), left and right, which form the largest and most developed part of the brain; initiation and coordination of all voluntary movement take place within the cerebrum. The basal ganglia are located immediately below the cerebrum.

chorea - rapid, jerky, dance-like movement of the body.

computed tomography scan (also called a CT or CAT scan) - a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce horizontal, or axial, images (often called slices) of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general x-rays.

cortex - the outer layer of the cerebrum, densely packed with nerve cells.

cryothalamotomy - a surgical procedure in which a super-cooled probe is inserted into a part of the brain called the thalamus in order to stop tremors.


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delusions - a condition in which the patient has lost touch with reality and experiences hallucinations and misperceptions.

dementia - not a disease itself, but group of symptoms that characterize diseases and conditions; it is commonly defined as a decline in intellectual functioning that is severe enough to interfere with the ability to perform routine activities.

dendrite - a threadlike extension from a nerve cell that serves as an antenna to receive messages from the axons of other nerve cells.

dopa decarboxylase - an enzyme present in the body that converts levodopa to dopamine.

dopamine - a chemical substance, a neurotransmitter, found in the brain that regulates movement, balance, and walking.

dyskinesia - an involuntary movement including athetosis and chorea.

dysphagia - difficulty in swallowing.

dystonia - a slow movement or extended spasm in a group of muscles.

dystrophin - a protein; a chemical substance made by muscle fibers.


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electrodiagnostic tests (i.e., electromyography and nerve conduction velocity) - studies that evaluate and diagnose disorders of the muscles and motor neurons. Electrodes are inserted into the muscle, or placed on the skin overlying a muscle or muscle group, and electrical activity and muscle response are recorded.

electroencephalogram (EEG) - a procedure that records the brain's continuous, electrical activity by means of electrodes attached to the scalp.

embolus - a "wandering" blood clot.

encephalitis - a viral infection of the brain.

epilepsy (also called seizure disorder) - a brain disorder involving recurrent seizures.

euphoria - a feeling of well-being or elation; may be drug-related.

evoked potentials - procedures that record the brain's electrical response to visual, auditory, and sensory stimuli.

extensor muscle - any muscle that causes the straightening of a limb or other part.

extrapyramidal system - system consisting of nerve cells, nerve tracts, and pathways that connects the cerebral cortex, basal ganglia, thalamus, cerebellum, reticular formation, and spinal neurons that is concerned with the regulation of reflex movements such as balance and walking.


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festination - walking with a series of quick, small, shuffling steps as if hurrying forward to keep balance.

flexor muscle - any muscle that causes the bending of a limb or other body part.


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ganglion - a cluster of nerve cells.

gray matter - the darker-colored tissues of the central nervous system; in the brain, the gray matter includes the cerebral cortex, the thalamus, the basal ganglia, and the outer layers of the cerebellum.

Guillain-Barré syndrome - A disorder in which the body's immune system attacks part of the nervous system.


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headache (primary) - includes tension (muscular contraction), vascular (migraine), and cluster headaches not caused by other underlying medical conditions.

headache (secondary) - includes headaches that result from other medical conditions. These may also be referred to as traction headaches or inflammatory headaches.


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incontinence - involuntary voiding of the bladder or bowel.

intracranial pressure (ICP) - the pressure inside the skull.


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levodopa (L-dopa) - the single most effective anti-Parkinson drug; it is changed into dopamine in the brain.

Lewy body - A pink-staining sphere, found in the bodies of dying cells, that is considered to be a marker for Parkinson's disease.

lordosis (also called sway-back) - an exaggeration of the forward curve of the lower part of the back.

lumbar puncture (also called spinal tap) - a special needle is placed into the lower back, into the spinal canal. This is the area around the spinal cord. The pressure in the spinal canal and brain can then be measured. A small amount of cerebral spinal fluid (CSF) can be removed and sent for testing to determine if there is an infection or other problems. CSF is the fluid that bathes the brain and spinal cord.


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magnetic resonance imaging (MRI) - 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.

meningitis - an inflammation of the meninges, the membranes that cover the brain.

micrographia - a change in handwriting with the script becoming smaller and more cramped.

monoamine oxidase (MAO) - an enzyme that breaks down dopamine. There are two types of MAO "A" and "B." In Parkinson's disease, it is beneficial to block the activity of MAO B.

multiple sclerosis (MS) - a disease of the central nervous system that is an unpredictable condition that can be relatively benign, disabling, or devastating, leaving the patient unable to speak, walk, or write.

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.

myelogram - a procedure that uses dye injected into the spinal canal to make the structure clearly visible on x-rays.

myoclonus - jerking, involuntary movements of the arms and legs; may occur normally during sleep.


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neuron - a cell specialized to conduct and generate electrical impulses and to carry information from one part of the brain to another.

neurosonography - a procedure that uses ultra high-frequency sound waves that enable the physician to analyze blood flow in cases of possible stroke.

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).

nigral - of or referring to the substantia nigra.

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.


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on-off effect, on-off phenomena - a change in the patient's condition, with sometimes rapid fluctuations between uncontrolled movements and normal movement, usually occurring after long-term use of levodopa and probably caused by changes in the ability to respond to this drug.

orthostatic hypotension - a large decrease in blood pressure upon standing; may result in fainting.


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pallidotomy - a surgical procedure in which a part of the brain, called the globus pallidus, is lesioned in order to improve symptoms of tremor, rigidity, and bradykinesia.

palsy - paralysis of a muscle or group of muscles.

parkinsonism - the name given to a group of disorders with similar features - four primary symptoms (tremor, rigidity, postural instability, and bradykinesia) that are the result of the loss of dopamine-producing brain cells.

Parkinson's disease (PD) - The most common form of parkinsonism; a slowly progressing, degenerative disease that is usually associated with the following symptoms, all of which result from the loss of dopamine-producing brain cells: tremor or trembling of the arms, jaw, legs, and face; stiffness or rigidity of the limbs and trunk; bradykinesia (slowness of movement); postural instability, or impaired balance and coordination.

peristalsis - wavelike contractions that move food through the digestive tract.

positron emission tomography (PET) scan - a computer-based imaging technique that provides a picture of the brain's activity rather than its structure by measuring levels of injected glucose which are labeled with a radioactive tracer.

pyramidal pathway - a collection of nerve tracts that travel from the cerebral cortex through the pyramid of the medulla oblongata in the brainstem to the spinal cord. Within the pyramid of the medulla, fibers cross from one side of the brain to the opposite side of the spinal cord; the pyramidal pathway is intact in Parkinson's disease.


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range of motion - the extent that a joint will move from full extension to full flexion.

resting tremor - a tremor of a limb that increases when the limb is at rest.

retropulsion - the tendency to step backwards if bumped from the front or upon initiating walking; usually seen in patients who tend to lean backwards because of problems with balance.

rigidity - increased resistance to the passive movement of a limb.


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seizure - occurs when part(s) of the brain receives a burst of abnormal electrical signals that temporarily interrupts normal electrical brain function.

serotonin - a chemical necessary for communication between certain nerve cells.

sialorrhea - drooling.

somatostatin - a chemical necessary for communication between certain nerve cells.

spasm - a condition in which a muscle or group of muscles involuntarily contract.

spinal cord - a bundle of nerves that carries messages between the brain and the rest of the body.

spinal tap (also called a lumbar puncture) - a special needle is placed into the lower back, into the spinal canal. This is the area around the spinal cord. The pressure in the spinal canal and brain can then be measured. A small amount of cerebral spinal fluid (CSF) can be removed and sent for testing to determine if there is an infection or other problems. CSF is the fluid that bathes the brain and spinal cord.

striatum - part of the basal ganglia, it is a large cluster of nerve cells, consisting of the caudate nucleus and the putamen, that controls movement, balance, and walking; the neurons of the striatum require dopamine to function.

stroke (also called brain attack) - happens when brain cells die because of inadequate blood flow to the brain.

subarachnoid hemorrhage - a brain attack that occurs when a blood vessel on the surface of the brain ruptures and bleeds into the space between the brain and the skull (but not into the brain itself).

substantia nigra - a small area of the brain containing a cluster of black-pigmented nerve cells that produce dopamine which is then transmitted to the striatum.

sustention (postural) tremor - a tremor of a limb that increases when the limb is stretched.

synapse - a tiny gap between the ends of nerve fibers across which nerve impulses pass from one neuron to another; at the synapse, an impulse causes the release of a neurotransmitter, which diffuses across the gap and triggers an electrical impulse in the next neuron.


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thrombus - a blood clot.

tremor - a rhythmical shaking of a limb, head, mouth, tongue, or other part of the body.

tyrosine - the amino acid from which dopamine is made.


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white matter - nerve tissue that is paler in color than gray matter because it contains nerve fibers with large amounts of insulating material (myelin). The white matter does not contain nerve cells. In the brain, the white matter lies within the gray layer of the cerebral cortex.


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x-ray - a diagnostic test which uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film.


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