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Home >> Multiple Sclerosis >> Further Information >> Glossary

Glossary

A

Acetylcholine
One of the chemicals (neurotransmitters) in the body that nerves use to communicate with each other.

Adrenalin
Epinephrine) Substance secreted into the bloodstream, which is reacted to by specialized receptors throughout the body and initiates the "flight-or-fight" response.

Analgesic
A substance that relieves pain.

Antibody
Serum Protein produced by the immune system's cells that binds to antigen.

Anticholinergic
Refers to the action of certain medications commonly used in the management of neurogenic bladder dysfunction. These medications inhibit the transmission of parasympathetic nerve impulses and thereby reduce spasms of smooth muscle in the bladder.

Antidepressant
Substances to treat depression or sadness. Examples include heterocyclic types such as Elavil, MAO inhibitors like phenelzine, or lithium carbonate.

Antigen
Any substance that triggers the immune system to produce an antibody; generally refers to infectious or toxic substances. See Antibody.

Antiviral
Agent that experimentally inhibits the proliferation and viability of infectious viruses. The method of action varies. Some agents will slow or inhibit the absorption or random initial attachment of viruses, some extend the lifespan of infected target cells, while others speed up several aspects of immunity, including complement, antibody, and phagocytosis responses.

Astrocyte
Large cell found in the white and grey matter of the central nervous system that has several roles in the development, structure and cell support of the brain and spinal cord.

Ataxia
Lack of coordination and unsteadiness that result from the brain's failure to regulate the body's posture and the strength and direction of limb movements. Most often caused by disease activity in the cerebellum.

Atrophy
Wasting or decrease in size of a part of the body because of disease or lack of use.

Attack
See Exacerbation.

Auditory evoked potentials (BAEPs)
Test in which the brain's electrical activity in response to auditory stimuli (e.g., clicking sounds) is recorded by an electroencephalograph and analyzed by computer. Demyelination results in a slowing of response time. This test is sometimes useful in the diagnosis of MS because it can confirm the presence of a suspected lesion or identify the presence of a lesion that has produced no symptoms. BAEPs have been shown to be less useful in the diagnosis of MS than either visual or somatosensory evoked potential tests.

Autoimmune
A condition caused by inflammation and destruction of tissue by the bodys own immune system.

Autoimmune disease
Process in which the body's immune system causes illness by mistakenly attacking healthy cells, organs, or tissues in the body that are essential for good health. Multiple Sclerosis is believed to be an autoimmune disease, along with systemic lupus rheumatoid arthritis, scleroderma, and many others. The precise origin and an understanding of how these diseases occur are not yet well known.

Autonomic nervous system
Part of the nervous system that regulates involuntary vital functions, including the activity of the cardiac (heart) muscle, smooth muscles (e.g., of the gut), and glands. The autonomic nervous system has two divisions: the sympathetic nervous system accelerates heart rate, constricts blood vessels, and raises blood pressure; the parasympathetic nervous system slows heart rate, increases intestinal and gland activity, and relaxes sphincter muscles.

Axon
It is through axons that impulses are transmitted to other nerve cells or to parts of the body directly stimulated by nerves (i.e. muscles, organs). In the nervous system, the axon is covered by a myelin sheath, and together they form the nerve fibre. Many thousands of these fibres, bundled together, form the anatomical structure known as the nerve.

B

B lymphocyte
Lymphocyte that matured in the bone marrow produces antibody.

B-cell
Type of lymphocyte (white blood cell) manufactured in the bone marrow that makes antibodies.

Benign MS
Relapsing-remitting MS, in which accumulated disability after a long period (usually in the range of 10-20 years) is either non-existent or very limited.

Blood-brain barrier (BBB)
Semi-permeable cell layer around blood vessels in the brain and spinal cord that prevents large molecules, cells, and potentially damaging substances and disease-causing organisms (e.g., viruses) from passing out of the blood stream into the central nervous system (brain and spinal cord).

Brainstem
Part of the central nervous system that houses the nerve centres of the head as well as the centres for respiration and heart control. It extends from the base of the brain to the spinal cord.

Burden of disease
Total amount of brain tissue affected by the MS disease process. It can be measured as a volume or an area, generally using MRI T2 weighted scans.

C

Catheter
Hollow, flexible tube, made of plastic or rubber, which can be inserted through the urinary opening into the bladder to drain excess urine that cannot be excreted normally.

Central Nervous System (CNS)
Collective term for the brain, spinal cord and optic nerve.

Cerebellum
Part of the brain situated above the brainstem that controls balance and coordination of movement.

Cerebrospinal fluid (CSF)
Watery, colourless, clear fluid found in the ventricles (pockets) of the brain, and surrounding the spinal cord. Certain changes in CSF that are characteristic of MS can be detected with a lumbar puncture (spinal tap), a test sometimes used to help make the MS diagnosis. See Lumbar puncture.

Cerebrum
Main portion of the brain, occupying the upper part of the cranial activity. Divided into two hemispheres joined by the corpus callosum, an arched mass of white matter, it forms the largest part of the human central nervous system.

Clinical trial
Formal test of a medical procedure or pharmaceutical agent.

Clonus
Sign of spasticity in which involuntary shaking or jerking of the leg occurs when the toe is placed on the floor with the knee slightly bent. The shaking is caused by repeated, rhythmic, reflex muscle contractions.

Cognition
High-level functions carried out by the human brain, including comprehension and use of speech, visual perceptions and construction, calculation ability, attention (information processing), memory, and executive functions such as planning, problem-solving and self-monitoring.

Complement
Large body of blood proteins (over 20), initiated in the liver, and involved in nearly all aspects of immunity and non-specific resistance.

Corticosteroids
Natural steroid hormones or man-made drugs, usually used to suppress inflammation and therefore having cortisone-like functions.

Cortisone
A glucocorticoid steroid hormone, produced by the adrenal glands or synthetically, that has anti-inflammatory and immune-system suppressing properties. Prednisone and prednisolone also belong to this group of substances.

Cranial nerves
Nerves that carry sensory, motor, or parasympathetic fibres to the face and neck. Included among this group of twelve nerves are the optic nerve (vision), trigeminal nerve (sensation along the face), vagus nerve (pharynx and vocal cords). Evaluation of cranial nerve function is part of the standard neurological exam.

D

DNA
Abbreviation for deoxyribonucleic acid a long molecule that forms a chromosome and that contains the complete code for cell and body development.

Dementia
A generally profound and progressive loss of intellectual function, sometimes associated with personality change, that results from loss of brain substance, and is sufficient to interfere with a person's normal, functional activities.

Demyelination
Destruction of the myelin in the central nervous system that results in interruptions of communication between neurons. Regions of demyelination are called plaques.

Disability
As defined by the World Health Organization, a disability (resulting from an impairment) is a restriction or lack of ability to perform an activity in the manner or within the range considered normal for a human being.

Disease modifying Drugs (DMD)
These therapies include beta interferons, glatiramer acetate and immunosuppressants (natalizumab, mitoxantrone). Disease modifying drugs are essential to modify the course of MS. They are currently the most effective way of controlling the course of MS.

Dysarthria
Poorly articulated speech resulting from dysfunction of the muscles controlling speech, usually caused by damage to the central nervous system or a peripheral motor nerve. The content and meaning of the spoken words remain normal.

E

Electroencephalography (EEG)
Diagnostic procedure that records, via electrodes attached to various areas of the person's head, electrical activity generated by brain cells.

Euphoria
Unusual level of cheerfulness and optimism, accompanied by a lessening of critical faculties; generally considered to be a result of damage to the brain.

Evoked potentials (EPs)
Recordings of the nervous system's electrical response to the stimulation of specific sensory pathways (e.g. visual, auditory, general sensory). In tests of evoked potentials, a person's recorded responses are displayed on an oscilloscope and analyzed on a computer that allows comparison with normal response times. Demyelination results in a slowing of response time. EPs can demonstrate lesions along specific nerve pathways whether or not the lesions are producing symptoms, thus making this test useful in confirming the diagnosis of MS.

Exacerbation
Appearance of new symptoms or the aggravation of old ones, lasting at least twenty-four hours (synonymous with attack, relapse, flare-up, bout,or worsening); usually associated with inflammation and demyelination in the brain and/or spinal cord.

F

Flare-up
see Exacerbation

Flexor spasm
Involuntary, sometimes painful contractions of the flexor muscles, which pull the legs upward into a clenched position. These spasms, which last two to three seconds, are symptoms of spasticity. They often occur during sleep, but can also occur when the person is in a seated position.

G

Gadolinium
Contrast medium injected prior to MRI scans. It passes through breaches in the blood-brain barrier and is therefore used to highlight new and active lesions. The usage of gadolinium greatly enhances the sensitivity of T1-weighted MRI.

Glucocorticoid hormones
Steroid hormones that are produced by the adrenal glands in response to stimulation by adrenocorticotropic hormone (ACTH) from the pituitary. These hormones, which can also be manufactured synthetically (prednisone, prednisolone, methylprednisolone, betamethasone, dexamethasone), serve both an immunosuppressive and an anti-inflammatory role in the treatment of MS exacerbations: they damage or destroy certain types of T-lymphocytes that are involved in the overactive immune response and interfere with the release of certain inflammation-producing enzymes.

Glycoprotein
Proteins that contain sugars.

H

Handicap
As defined by the World Health Organisation; a handicap is a disadavantage, resulting from an impairment or a disability that interferes with a person's efforts to fulfil a role that is normal for that person. Handicap is therefore a social concept, representing the social and environmental consequences of a person's impairments and disabilities.

Hemiparesis
Weakness of one side of the body, including one arm and one leg.

Hemiplegia
Paralysis of one side of the body, including one arm and one leg.

I

Immune system
Complex system of various types of cells that protects the body against disease-producing organisms and other foreign invaders.

Immunity
Ability to resist infection and to heal. The process may involve acquired immunity, (the ability to learn and remember a specific infectious agent), or innate immunity (the genetically programmed system of responses that attack, digest, remove, and initiate inflammation and tissue healing).

Immunoglobulin G (IgG)
An antibody produced by human plasma cells. It is also found in plaques of a diseased central nervous system. Levels of IgG are increased in the cerebrospinal fluid of most MS patients.

Immunosuppression
In MS, form of treatment that slows or inhibits the body's natural immune responses, including those directed against the body's own tissues. Examples of immunosuppressive treatments in MS include cyclosporin, methotrexate, and azathioprine.

Impairment
As defined by the World Health Organization, an impairment is any loss or abnormality of psychological, physiological, or anatomical structure or function. It represents a deviation from the person's usual biomedical state. An impairment is thus any loss of function directly resulting from injury or disease.

Incontinence
Also called spontaneous voiding; the inability to control passage of urine or bowel movements.

Inflammation
Tissue's immunologic response to injury, characterized by mobilization of white blood cells and antibodies, swelling, and fluid accumulation.

Intravenous
Within a vein; often used in the context of an injection into the vein of a medication dissolved in a liquid.

J

K

L

L'Hermitte's sign
Abnormal sensation of electricity or "pins and needles" going down the spine into the arms and legs that occurs when the neck is bent forward so that the chin touches the chest.

Lesion
See Plaque.

Lesion load
Total volume of brain tissue affected by the MS disease process (as seen on MRI T2-weighted scans).

Limbic system
Functional, not physical, system in the brain, generally considered to mediate emotions with metabolism.

Lumbar puncture
Diagnostic procedure that uses a hollow needle (canula) to penetrate the spinal canal at the level of third-fourth or fourth-fifth lumbar vertebrae to remove cerebrospinal fluid for analysis. This procedure is used to examine the cerebrospinal fluid for changes in composition that are characteristic of MS (e.g., elevated white cell count, elevated protein content, the presence of oligoclonal bands).

Lymphocyte
Specialized cells of the immune system, which recognize antigens and subsequently release substances which activate other cells, or directly destroy the antigen. Lymphocytes are divided into two main groups: T-lymphocytes and B-lymphocytes.

M

MRI
See Magnetic resonance imaging.

Macrophage
Large white blood cells, which have an important role in defending the body against invasion by bacteria.

Magnetic resonance imaging (MRI)
Imaging technique based on detection of the response of different molecules to strong magnetic fields. It produces visual images of different body parts without the use of X-rays and can therefore be performed repeatedly.
The nuclei of atoms are influenced by a high frequency electromagnetic impulse inside a strong magnetic field. The nuclei then give off resonating signals, producing pictures of parts of the body. MRI allows the neurologist to identify MS lesions in the brain and spinal cord, at different stages of their development.
MRI is an important diagnostic tool for MS but it is also more and more used to detect disease progression in seemingly stable patients. MRI is very sensitive and able to detect ten times more disease activity than what is visible through clinical manifestations alone.

Magnetically evoked responses
An alteration in the electrical activity of a region of the nervous system through which an incoming sensory stimulus is passing. It is based on detection of the response of cell nerves to magnetic fields.

Monoclonal antibodies
Laboratory-produced antibodies, which can be programmed to react against a specific antigen in order to suppress the immune response.

Multiple Sclerosis (MS)
Autoimmune disease of the central nervous system, mainly affecting young adults, whose origin is unknown. It damages nerve fibre insulation (myelin) in a random and patchy manner, causing a wide range of neurological defects. It is characterized clinically by symptoms that typically abate spontaneously in the early years of the disease but often get gradually worse in later years.

Muscle spasm
A painful and involuntary muscle contraction.

Muscle tone
Characteristic of a muscle brought about by the constant flow of nerve stimuli to that muscle, which describes its resistance to stretching. Abnormal muscle tone can be defined as: hypertonus (increased muscle tone, as in spasticity); hypotonus (reduced muscle tone; flaccid paralysis); atony (loss of muscle tone). Muscle tone is evaluated as part of the standard neurological exam in MS.

Myelin
Soft, white coating composed of lipids (fats) and protein, surrounding nerve fibres in the central nervous system. A complex natural electrical insulator, myelin serves to speed up the conduction of electrochemical messages between the central nervous system and the rest of the body.

Myelin basic protein (MBP)
Major component of myelin. When damage to the myelin occurs (as in MS), MBP can often be found in abnormally high levels in the patient's cerebrospinal fluid.

Myelin sheath
A discontinuous layer of fatty protein that insulates the axon, allowing more efficient transmission of nerve signals.

N

Necrosis
Death of tissue or cells, either from infection or the loss of normal circulation and autotoxicity.

Nerve
Bundle of nerve fibres (axons). The fibres are either afferent (leading toward the brain and serving in the perception of sensory stimuli of the skin, joints, muscles, and inner organs) or efferent (leading away from the brain and mediating contractions of muscles or organs).

Nerve fibres
The axon of a nerve cell, in the brain, spinal cord and in peripheral nerves.

Nervous system
Includes all of the neural structures in the body: the central nervous system consists of the brain, spinal cord, and optic nerves; the peripheral nervous system consists of the nerve roots, nerve plexi, and nerves throughout the body.

Neuralgia
Pain, sometimes severe, that manifests along the length of a nerve and arises within the nerve itself, not in the tissue from which the sensation seems to arise.

Neuritis
Nerve inflammation, usually with direct nerve damage, part of a degenerative process.

Neurologist
Physician who specializes in the diagnosis and treatment of conditions related to the nervous system.

Neuron
The basic nerve cell of the nervous system. A neuron consists of a nucleus within a cell body and one or more processes (extensions) called dendrites and axons. Neurons generate electrical impulses and communicate information throughout the nervous system.

O

Oligoclonal bands
Diagnostic sign indicating abnormal levels of certain antibodies in the cerebrospinal fluid; seen in approximately 90 percent of people with Multiple Sclerosis, but not specific to MS.

P

Paralysis
Inability to move a part of the body.

Paraparesis
A weakness but not total paralysis of the lower extremities (legs).

Paraplegia
Paralysis of both lower extremities (legs).

Parasympathetic Nervous System
Division of the autonomic nervous system that controls normal digestive, reproductive, cardiopulmonary, and vascular functions and stimulates most secretions. This subsystem works as a direct antagonist to the sympathetic division, and functions are balanced by their interaction.

Paresis
Partial or incomplete paralysis of a part of the body.

Paresthesias
A sensation of pricking, tingling, or creeping on the skin having no objective cause and usually associated with injury or irritation of a sensory nerve or nerve root.

Paroxysmal symptom
Any one of several symptoms that have sudden onset, apparently in response to some kind of movement or sensory stimulation, last for a few moments, and then subside. Paroxysmal symptoms tend to occur frequently in those individuals who have them, and follow a similar pattern from episode to the next. Examples include acute episodes of trigeminal neuralgia (sharp facial pain), tonic seizures (intense spasm of limb or limbs on one side of the body), dysarthia (slurred speech often accompanied by loss of balance and coordination), and various paresthias (sensory disturbances ranging from tingling to severe pain).

Physiotherapist
Individuals trained to evaluate and improve movement and function of the body, with particular attention to physical mobility, blance, posture, fatigue and pain. The physical therapy program typically involves (1) educating the person with MS about the physical problems caused by the disease, (2) designing an individualized exercise program to address the problems, and (3) enhancing mobility and energy conservation through the use of a variety of mobile aids.

Plaque
An area of inflamed or demyelinated central nervous system tissue.

Primary progressive MS (PPMS)
Clinical course of MS characterized from the beginning by progressive disease, with no plateaus or remissions, or an occasional plateau and very short-lived, minor improvements.

Protein
Molecule made of a chain of amino acids.

Q

Quadriplegia
Paralysis of both arms and both legs.

R

Receptor
Protein found on the surface of a cell. It serves as a recognition site for other cells and proteins or a "docking" site for various molecules.

Reflex
Involuntary response of the nervous system to a stimulus, such as the stretch reflex, which is elicited by tapping a tendon with a reflex hammer, resulting in a contraction. Increased, diminished, or absent reflexes can be indicative of neurologic damage, including MS, and are therefore tested as part of the standard neurological exam.

Relapse
See Exacerbation.

Relapsing-remitting MS
Clinical course of MS that is characterized by the occurrence of new symptoms or the worsening of old symptoms (relapses or exacerbations). Symptoms may evolve over several days or weeks and then fully or partially disappear. The pattern of attacks is unpredictable even in the same person. RRMS accounts for approximately 40% of the patient population with MS at any given time.

Remission
Lessening in the severity of symptoms or a "return" to the level of health equal (or similar) to the one experience prior to the last attack.

Remyelination
Repair of damaged myelin. Some myelin repair may occur spontaneously in MS but is usually a very slow and uncontrollable process.

S

Secondary progressive MS
A clinical course of MS that initially is relapsing-remitting and then becomes progressive at a variable rate, possibly with an occasional relapse and minor remission.

Sensory
Related to bodily sensations such as pain, smell, taste, temperature, vision, hearing, acceleration, and position in space.

Sign
An objective physical problem or abnormality identified by the physician during the neurologic examination. Neurologic signs may differ significantly from the symptoms reported by the patient because they are identifiable only with specific tests and may cause no overt symptoms. Common neurologic signs in Multiple Sclerosis include altered eye movements and other changes in the appearance or function of the visual system; altered reflexes; weakness; spasticity; circumscribed sensory changes.

Somatosensory evoked potential
A test that measures the brain's electrical activity in response to repeated (mild) electrical stimulation of different parts of the body. Demyelination results in a slowing of response time. This test is useful in the diagnosis of MS because it can confirm the presence of a suspected lesion (area of demyelination) or identify the presence of an unsuspected lesion that has produced no symptoms.

Spasticity
Abnormal increase in muscle tone, manifested as a spring-like resistance to moving or being moved.

Spinal cord
It is the cylindrical part of the central nervous system. It is the thick cord of nervous tissue that extends from the brain along the back in the cavity of the spinal column and carries nerve impulses to and from the brain.

Spinal tap
See Lumbar puncture.

Sympathetic
A division of the autonomic or involuntary nervous system that works in general opposition to the parasympathetic division. Many of the sympathetic functions are local, specific, and involve secretion of acetylcholine, stimulating or suppressing a specific muscle, gland, etc. A certain number of these nerves, however, secrete epinephrine (adrenalin) and norepinephrine (noradrenalin). These are called adrenergic. Since the adrenal medulla also secretes the same substances into the bloodstream as hormones, all the muscles or glands that are affected by the adrenergic sympathetic nerves also react to the epinephrine secreted into the blood. This forms the basis for a potentially lifesaving emergency fight or flight response and is meant for short, drastic activities. A chronic excess of the adrenergic response, however, is a major cause of stress.

Symptom
A subjectively perceived problem or complaint reported by the patient. In Multiple Sclerosis, common symptoms include visual problems, fatigue, sensory changes, weakness or paralysis of limbs, tremor, lack of coordination, poor balance, bladder or bowel changes, and psychological changes.

T

T-cell
A lymphocyte (white blood cell) that develops in the bone marrow, matures in the thymus, and works as part of the immune system in the body.

T-suppressor cells
These cells close down the immune response after it has destroyed invading organisms.

T1 weighted scans
Abnormalities detected on T1-weighted scans indicate new sites of inflammations. See also Gadolinium.

T2 weighted scans
Abnormalities on T2-weighted scans correspond to either active or inactive lesions. The total volume of T2-weighted lesions (also called Lesion load or Burden of disease) is an indication of the total volume of brain tissue affected by the MS disease process.

Tissue
Similar cells united as a group to perform a specific function.

Tremor
Rhythmical/alternating movement that may affect any part of the body.

Trigeminal neuralgia
Lightning-like, acute pain in the face caused by demyelination of nerve fibres at the site where the sensory (trigeminal) nerve root for that part of the face enters the brainstem.

Tumours
An abnormal mass of tissue that results from excessive cell division that is uncontrolled and progressive.

U

V

Visual evoked potential
A test in which the brain's electrical activity in response to visual stimuli (e.g., a flashing checkerboard) is recorded by an electroencephalograph and analyzed by computer. Demyelination results in a slowing of response time. Because this test is able to confirm the presence of a suspected brain lesion (area of demyelination) as well as identify the presence of an unsuspected lesion that has produced no symptoms, it is extremely useful in diagnosing MS. VEPs are abnormal in approximately 90 percent of people with MS.

W

White blood cells
Blood cells that are involved with host defences against infection.

White matter
The part of the brain that contains myelinated nerve fibres and appears white, in contrast to the cortex of the brain, which contains nerve cell bodies and appears grey.

X

Y

Z


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