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Glossary of ALS Terms

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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 using the toilet; 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 wishes for medical care should he or 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 screaming, shouting, complaining, moaning, cursing, pacing, fidgeting or wandering pose risk or discomfort, become disruptive or unsafe or interfere with the delivery of care.
  • agonist - a drug that increases neurotransmitter activity by directly stimulating the nerve cell receptors.
  • akinesia - no movement.
  • ataxia - loss of balance.
  • Alzheimer's disease - A progressive, degenerative brain disease that 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 (angiogram) - an X-ray scan of arteries going to and through the brain. Patients who have arteriograms first are injected with a radiopaque dye.
  • athetosis - slow, involuntary movements of the hands and feet.
  • atrophy - wasting and shrinkage of tissue.
  • axon - the long, hairlike extension of a nerve cell that carries a message to the next nerve cell.


  • basal ganglia - several large clusters of nerve cells, including the striatum and the substantia nigra, 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 30 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 - another term for stroke.
  • brisk reflex - a condition that describes the deterioration of the upper motor nerve cells (neurons).
  • bulbar muscles - the muscles that control the speech, chewing and swallowing.


  • central nervous system - the brain and the spinal cord.
  • cerebral embolism - a situation in which a wandering clot (embolus) or some other particle lodges in a blood vessel in the brain.
  • cerebral hemorrhage - a type of stroke occurs when a defective artery in the brain bursts, flooding the surrounding tissue with blood
  • cerebral thrombosis - the most common type of brain attack, it occurs when a blood clot (thrombus) forms and blocks blood flow in an artery bringing blood to part of the brain.
  • cerebellum - a large, two-halved structure (hemispheres) located in the lower part of the brain that's responsible for the coordination of movement and balance.
  • cerebrospinal fluid analysis (spinal tap) - the withdrawing and examination of a small sample of the fluid that bathes the spinal cord.
  • cerebrum - the two largest, most complex and most developed lobes 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.
  • classical ALS - a progressive neurological disease characterized by a deterioration of upper and lower motor nerve cells (neurons). This type of ALS affects more than two-thirds of all people with ALS.
  • computed tomography (CT or CAT scan) - a non-invasive X-ray procedure that takes cross-sectional images of the brain or other internal organs. It detects abnormalities that may not show up on an ordinary x-ray.
  • cortex - the outer layer of the cerebrum, densely packed with nerve cells.
  • cryothalamotomy - a surgical procedure in which a supercooled probe is inserted into a part of the brain called the thalamus in order to stop tremors.


  • delusions - a condition in which the patient has lost touch with reality and experiences hallucinations and misperceptions.
  • dementia - not a disease itself, but a group of symptoms that characterize diseases and conditions. Dementia commonly is defined as a decline in intellectual functioning severe enough to interfere with the ability to perform routine activities.
  • dendrite - a threadlike extension from a nerve cell that acts like an antenna, receiving 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.
  • dysarthria - impaired speech and language due to weakness or stiffness in the muscles used for speaking.
  • 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.


  • electrodiagnostic tests - studies including electromyography (EMG) and nerve conduction velocity ( NCV), 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 method of recording the brain's continuous electrical activity by means of electrodes attached to the scalp.
  • embolus - a "wandering" blood clot.
  • encephalitis - an infection of the brain.
  • epilepsy - a brain disorder involving recurrent seizures; may also be called a seizure disorder.
  • euphoria - a feeling of well-being or elation; may be drug related.
  • evoked potentials - a procedure to record the brain's electrical response to visual, auditory and sensory stimuli.
  • exertional dyspnea - a condition characterized by shortness of breath during physical activity.
  • extensor muscle - any muscle that causes the straightening of a limb or other part.
  • extrapyramidal system (EPS) - the nerve cells, nerve tracts and pathways that connect the cerebral cortex, basal ganglia, thalamus, cerebellum, reticular formation, and spinal neurons. The EPS helps regulate reflex movements such as balance and walking.


  • familial ALS - a progressive neurological disease that affects more than one member of the same family. This type of ALS accounts for a very small number of people with ALS in the United States (5 to 10 percent).
  • fasciculations - non-painful, rapid and involuntary contractions or twitchings of groups of muscle fibers. This is often described by people with ALS as "persistent rolling beneath the skin."
  • festination - walking with a series of quick, small, shuffling steps as if hurrying forward to keep balance.
  • flaccid muscles (also hypotonicity) - a condition characterized by a decrease or loss of normal muscle tone due to the deterioration of the lower motor nerve cells.
  • flexor muscle - any muscle that causes the bending of a limb or other body part.


  • ganglion - a cluster of nerve cell bodies.
  • 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-Barre syndrome - A disorder in which the body's immune system attacks part of the nervous system.


  • 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.
  • hyperreflexia - excessive response of muscle reflexes when a normal stimulus is applied.
  • hyporeflexia - weak or absent muscle response when a normal stimulus is applied.


  • incontinence - involuntary voiding of the bladder or bowel.


  • 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 and thought to be a marker for Parkinson's disease.
  • lordosis - an exaggeration of the forward curve of the lower part of the back, sometimes called sway-back.
  • lower motor neurons - nerve cells (neurons) starting at the spinal cord or brain stem and ending at the muscle fibers.


  • magnetic resonance imaging (MRI) - a non-invasive, non-X-ray procedure that produces two-dimensional view of an internal organ or structure. MRI is especially useful for imaging the soft tissues of the brain and spinal cord.
  • 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. MAO comes in two forms: A and B. In Parkinson's disease, it is beneficial to block the activity of MAO B.
  • motor neuron diseases - a group of disorders in which motor nerve cells (neurons) in the spinal cord and brain stem deteriorate and die. ALS is the most common motor neuron disease.
  • multiple sclerosis (MS) - a disease of the central nervous system that is unpredictable. MS can be relatively benign, disabling, or devastating, leaving the patient unable to speak, walk, or write.
  • muscle cramps, unexpected - involuntary, painful shortening of muscles. Usually, a knotting of the muscles is visible.
  • muscle weakness - loss of muscle strength with increased fatigue, loss of coordination, difficulty with motor skills and lack of ability to carry out certain other skills.
  • muscular dystrophy - the name given to a group of diseases that are, for the most part, genetically determined and which 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.


  • 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 to reveal patterns of blood flow. It is commonly used to help confirm 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 involved in governing autonomic nervous system activity, especially blood pressure and heart rate.


  • 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.


  • 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.
  • 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, Parkinson's) - The most common form of parkinsonism, is 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.
  • palsy - paralysis of a muscle or group of muscles.
  • 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. The technique detects levels of injected glucose labeled with a radioactive tracer.
  • primary lateral sclerosis (PLS) - a progressive neurological disease in which the upper motor nerve cells (neurons) deteriorate. If the lower motor neurons are not affected within two years, the disease usually remains a pure upper motor neuron disease. This is the rarest of all forms of ALS.
  • progressive bulbar palsy (PBP) - a condition that begins with difficulties in speaking, chewing and swallowing due to lower motor nerve cell (neuron) deterioration. This disorder affects about 25 percent of all people with ALS.
  • progressive muscular atrophy (PMA) - a progressiveneurological disease in which the lower motor nerve cells (neurons) deteriorate. If the upper motor neurons are unaffected within two years, the disease usually remains a pure lower motor neuron disease.
  • pseudobulbar palsy - a condition characterized by difficulties with speech, chewing and swallowing. These symptoms resemble those of bulbar palsy, but this condition is also characterized by spontaneous or unmotivated crying and laughing.
  • 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.


  • range of motion - the extent that a joint will move from full extension to full flexion.
  • resting tremor - a tremor, in 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.


  • serotonin - a chemical necessary for communication between nerve cells.
  • sialorrhea - drooling.
  • somatostatin - a chemical necessary for communication between nerve cells.
  • spasm - a condition in which a muscle or group of muscles involuntarily contract.
  • spinal muscular atrophy (SMA) - a hereditary neurological disease in which only the lower motor nerve cells are affected.
  • 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 a "brain attack" - a cluster of symptoms that appear suddenly when brain cells die because of inadequate blood flow.
  • 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 cluster of black-pigmented nerve cells in the brain that produce dopamine. Messages from the substantia nigra are transmitted to the striatum.
  • sustention (postural) tremor - a limb tremor that increases when the limb is stretched.
  • synapse - a tiny gap between the ends of one nerve cell and the beginning of another. Impulses pass from one nerve cell to another at the synapse. Impulses traveling down one nerve cell cause the release of a neurotransmitter which diffuses across the gap and triggers an electrical impulse in the next neuron.


  • 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.


  • upper motor neurons - nerve cells (neurons) originating in the brain's motor cortex and running through the spinal cord.


  • 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.