Multiple Sclerosis Glossary

Active progressive MS	The term “active” when referring to either secondary progressive or primary progressive MS patients indicates the person has attacks or relapses in addition to having a progressive course
Active relapsing remitting MS	Patients with relapsing-remitting MS who have had relapses within the past 2 years and have new MS lesions on recent MRI scans.
Attack of MS	An acute or subacute worsening of relapsing-remitting MS. Synonymous with exacerbation or relapse
Brain atrophy	Shrinkage of the brain
Cells in the brain	The brain has three major cell types, neurons, oligodendrocytes, and astrocytes. Neurons have a cell body and an axon which is covered by a myelin sheath made by the oligodendrocyte.
Cerebrospinal fluid	The fluid which surrounds your brain and spinal cord.
Clinical trial	A randomized clinical trial (RCT) is a study that is done to show whether a new drug or treatment is effective in preventing or improving the outcome of a disease
Cohort studies	Studies following groups of MS patients
Degeneration	A later phase in MS where inflammation has slowed or stopped but continued central nervous system damage occurs
Demyelination	Inflammation in the central nervous system associated with multiple sclerosis destroys the myelin sheath on some axons. This destruction is called demyelination.
Disability	Defined as physical or mental conditions that limit a person’s movement, senses or activities.
Disease-modifying therapy (DMT)	A category of drugs used to slow down disease progression.
Dissemination in time	Refers to the presence of signs, symptoms, MRI findings, and cerebrospinal fluid findings which show that active inflammation in the central nervous system has occurred at more than one time in the past
Dissemination in space	Refers to different parts of the central nervous system showing evidence of inflammation in the past or present time.
EDSS	Expanded Disability Status Scale – The EDSS is the most widely used method of quantifying the complex neurological exam and level of disability in MS. It is used to monitor changes in the level of disability over time. The scale runs from a score of 0 to 10 with zero corresponding to no signs or symptoms of neurologic dysfunction and 10 representing death.
Exacerbation	An acute or subacute worsening of relapsing-remitting MS. Synonymous with “attack” or relapse
FLAIR image	Image made by an MRI scanner in which the grey matter appears a light grey and the white matter a darker grey but the fluid filled spaces appear white.
Gadolinium	A compound which appears white on t1 weighted MRI scans and can be infused into a vein in your arm when you have an MRI scan. With active brain inflammation, Gadolinium in the blood vessel leaks into the inflamed area making it appear white.
Inflammation	Inflammation is part of your body’s complex response to harmful stimuli which involves immune cells, blood vessels, and chemical mediators
McDonald Criteria	MRI criteria used to help in the diagnosis of MS
Mean	The average value of a group of values
Median	The “middle” value in the list of numbers. It is frequently used to report results in epidemiological studies rather than an average value because it is not significantly changed by a small number of high or low values (outliers) in the sample and thus may give a better idea of a typical value for the group. The average value, on the other hand may be pulled to on side or another by a few very high values or very low values
MRI	The term magnetic resonance imaging (MRI) refers to an imaging technique which is uses a magnetic field and radio waves to take picture of your brain, spinal cord, and optic nerve. (central nervous system). When you lie or sit in an MRI machine, you are inside of a big manet. The magnet causes water molecules in your body to move slightly to align themselves in a certain direction. Next, your body is exposed to radio waves which move the water molecules a little more. When the radio wave is turned off, the water molecules spring back to their original position. The energy they release when they spring back is emitted in the form of new radio waves which are sensed by the MRI machine and used to reconstruct images of the part of your body which is scanned. Different types of images can be reconstructed from the returning radio waves which help to identify normal and abnormal structures (or lesions) in your central nervous system. There are three main types of images used for MS patients. These are called T1 weighted images, T2 weighted images and FLAIR images. T1 weighted images are best to look at the overall structures of the brain. T2 and Flare images show the abnormalities of MS best.
Multiple Sclerosis Severity Score	An algorithm which allows you to compare individual EDSS scores with the distribution of EDSS in patients who have had MS for the same length of time
Placebo	A placebo is an inactive substance given to some of the participants in a randomized clinical trial.
Propensity score matching (PSM)	In the statistical analysis of observational data, propensity score matching (PSM) is a statistical matching technique that attempts to estimate the effect of a treatment, policy, or other intervention by accounting for the covariates that predict receiving the treatment. PSM attempts to reduce the bias due to confounding variables that could be found in an estimate of the treatment effect obtained from simply comparing outcomes among units that received the treatment versus those that did not. The possibility of bias arises because a difference in the treatment outcome (such as the average treatment effect) between treated and untreated groups may be caused by a factor that predicts treatment rather than the treatment itself. In randomized experiments, the randomization enables unbiased estimation of treatment effects; for each covariate, randomization implies that treatment-groups will be balanced on average, by the law of large numbers. Unfortunately, for observational studies, the assignment of treatments to research subjects is typically not random. Matching attempts to reduce the treatment assignment bias, and mimic randomization, by creating a sample of units that received the treatment that is comparable on all observed covariates to a sample of units that did not receive the treatment.
Relapse	A relapse is officially defined as new or worsening neurological symptoms with objective changes in the neurological exam in the absence of fever and last for more than 24 hours which have been preceded by a period of clinical stability of at least 30 days. Synonymous with exacerbation or attack
T1 weighted image	Image made by an MRI scanner in which the gray matter and white matter appear grey and the fluid filled spaces are black.
T2 weighted image	Images made by an MRI scanner in which the grey matter appears a light grey and the white matter a darker grey and the fluid filled spaces appear white.
McDonald Criteria	MRI criteria used to help in the diagnosis of MS
Relapse	A relapse is officially defined as new or worsening neurological symptoms with objective changes in the neurological exam in the absence of fever and last for more than 24 hours which have been preceded by a period of clinical stability of at least 30 days. Synonymous with exacerbation or attack
Symptomatic therapy or medication	A therapy designed to reduce the symptoms of a disease. Aspirin to lower the fever from an infection is an example of a symptomatic therapy
White matter	The area underneath the grey matter on the surface of the brain which contains the axons of the neurons which travel from one area of grey matter to other areas. Myelin covering these axons has a whitish appearance which lead to the label “white matter”.