Glossary of Movement Disorders Terms


A chemical messenger (neurotransmitter) released by cholinergic nerves in the striatum area of the brain. It is involved in many brain functions, including memory and control of motor activity. There appears to be an interplay between the actions of acetylcholine and dopamine.

Action tremor:

A tremor that occurs or increases when the hand is moving voluntarily.


Supplemental or secondary (but not essential) to the primary agent; sometimes used to describe medications to enhance levodopa therapy.


A chemical or drug that enhances the activity of a neurotransmitter such as dopamine.


Delay in initiating movement, inability to move, “freezing.”


Auxiliary; serving as an aid.


An agent that prevents the loss of oxygen in chemical reactions.


An agent or a class of medications that reduce anxiety.


A form of cell death in which cells shrink and disappear; sometimes referred to as “cell suicide.” In Parkinson’s disease, some scientists believe that the nerve cells in the substantia nigra portion of the brain die by apoptosis.


Loss of balance.


Slow, involuntary movements of the hands and feet (see Dyskinesia).

Autonomic nervous system:

The system that controls involuntary body functions.


Involuntary clinching of the eyelid.

Blood-brain barrier:

The protective membrane that separates the bloodstream from brain tissue.


Slowness of movement.


Slowness in thought processing.


Excessive involuntary movements, ranging from twisting or writhing to flailing movements of the extremities (see Dyskinesia).


A ratchet-like movement in the joints, characteristic of Parkinson’s disease.

CT Scan:

Computerized Tomography; a type of x-ray; also known as a CAT Scan.


False, fixed belief, not substantiated by sensory or objective evidence.


A range of symptoms such as disorientation, confusion, memory loss, impaired judgment, and alterations in mood and personality — symptoms can arise from a variety of causes

DNA (deoxyribonucleic acid):

The basic chemical substance that makes up the gene.


A chemical messenger (neurotransmitter) in the brain that controls movement.


Low voice volume or muffled speech.


Abnormal, involuntary body movements that can appear as jerking, fidgeting, twisting, and turning movements; frequently induced by Parkinson medications. Dystonia, athetosis, and chorea are forms of dyskinesias.


Difficulty in swallowing.


Involuntary spasms of muscle contraction which cause abnormal movements and postures (see Dyskinesia).


Originating internally; developing from within, rather than caused by external factors; the opposite of exogenous.

Essential tremor (ET):

A condition more common than Parkinson’s disease, which often includes shaking of the hands or head, and an unsteady quality of the voice.


The causes or origins of a disease. The etiology of Parkinson’s disease is not known.


Originating externally; arising from external rather than internal factors; the opposite of endogenous.


Short, shuffling steps.

Free radicals:

Toxic substances that are continuously produced by all cells of the human body.


Temporary, involuntary inability to take a step or initiate movement.

Half life:

The time taken for the concentration of a drug in the bloodstream to decrease by one-half. Drugs with a shorter half life must be taken more frequently.


Hearing sounds or seeing animals, objects or people that are not real.


Decreased facial expression due to rigidity of facial muscles.


Of unknown origin or without apparent cause (Idiopathic Parkinson’s disease).

Lewy bodies:

Pink-staining spheres found in nerve cells, considered to be a pathological marker for Parkinson’s disease.

Livido reticularis:

Purplish or bluish mottling of the skin caused by certain Parkinson medications.


Small, cramped handwriting.


A chemical produced during an attempt to make a synthetic narcotic. MPTP produces a condition that mimics Parkinson’s disease.


Abrupt, jerking movements of the arms or legs, usually occurring during sleep.

MRI: Magnetic Resonance Imaging:

Computerized images based on nuclear magnetic resonance of atoms within the body induced by radio waves.


Drugs that block dopamine receptors, usually prescribed to treat psychiatric symptoms.


A cell that generates or conducts electrical impulses to carry information from one part of the brain to another.


A chemical substance (such as dopamine, acetylcholine, or norepinephrine) that carries impulses from one nerve cell to another.

Neurotrophic factors:

Substances that prevent nerve cells from dying.


Chemical transmitter involved in regulating the involuntary nervous system.

Off-On phenomenon:

Sudden, unpredictable changes in motor performance by people on levodopa therapy.

Orthostatic hypotension:

A drop in blood pressure upon standing; can cause fainting.


Paralysis of a muscle group.


The production or development of a disease.

PET (positron emission tomography):

An imaging method that allows one to see brain dopamine systems using an injection of a radioactive substance.

Postural tremor:

The rhythmic shaking of the hands with arms outstretched.

Resting tremor:

One of the primary symptoms of Parkinson’s disease; typically present in arm, leg, lips, chin or tongue; tremor occurs or worsens when at rest; decreases with active motions.


Increased resistance to the passive movement of a limb.


The area of the brain that controls movement, balance and walking.

Substantia nigra:

The area of the brain where cells produce dopamine.

Wearing-off phenomenon:

Reduced effectiveness of levodopa prior to the scheduled time for the next dose, resulting in decreased motor performance