These are some multiple sclerosis (MS) terms to know. Of course, a definition is only part of truly understanding something. 



Medications capable of preventing or relieving spasms or convulsions.


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 or its connections with other parts of the brain.


See Exacerbation.

Autoimmune Disease

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


Bell's Palsy

Paralysis of the facial nerve, which can occur as a consequence of MS, viral infection, or other infections. It has acute onset and can be transient or permanent.

Blood-Brain Barrier (BBB)

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


Central Nervous System (CNS)

Collective term for the major part of the nervous system that is principally composed of the brain and spinal cord.


Of long duration; not acute.

Cog Fog

A feeling of confusion or lack of mental clarity brought on by cognition issues related to MS. This cognitive symptom is common in people with MS and is also known as “brain fog.”


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

Combined Bladder Dysfunction

Type of neurogenic bladder dysfunction in RMS (also called detrusor-external sphincter dyssynergia [DESD]). Simultaneous contractions of the bladder's detrusor muscle and external sphincter cause urine to be trapped in the bladder, resulting in symptoms of urinary urgency, hesitancy, dribbling, or incontinence.


Condition in which bowel movements happen less frequently than is normal for the particular individual or the stool is small, hard, and difficult or painful to pass.


Permanent shortening of the muscles and tendons adjacent to a joint, which can result from severe, untreated spasticity and interferes with normal movement around the affected joint. If left untreated, the affected joint can become frozen in a fixed position.


Often known as steroids, corticosteroids are an anti-inflammatory medicine prescribed for a wide range of conditions.

Cranial Nerves

Nerves that carry sensory, motor, or parasympathetic fibers to the face and neck. Included among this group of 12 nerves are the optic nerve (vision), trigeminal nerve (sensation along the face), oculomotor nerve (eye movement), facial nerve, auditory nerve, and vagus nerve (pharynx and vocal cords). Evaluation of cranial nerve function is part of the standard neurological exam.



Destruction of the myelin sheath—which surrounds the axons, or nerve fibers, in the CNS—that results in interruptions of communications between neurons. Regions of demyelination cause interruptions in the conduction of nerve impulses.


A mood disorder marked especially by sadness, inactivity, difficulty with thinking and concentration, a significant increase or decrease in appetite and time spent sleeping, feelings of dejection and hopelessness, and, sometimes, suicidal thoughts or an attempt to commit suicide.


Double vision or the simultaneous awareness of 2 images of the same object that results from a failure of the 2 eyes to work in a coordinated fashion.


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

Disease-Modifying Therapies (DMTs)

Disease-modifying therapies have been shown in clinical trials to modify the course of MS.

Double-Blind Clinical Study

A study in which neither the subjects (ie, patients) nor the examining healthcare providers (or attending nurses, or any other research staff) know who is taking the test drug and who is taking a control or placebo agent.


Impairment of sensitivity, especially to touch.


Expanded Disability Status Scale (EDSS)

A method of quantifying disability in MS and monitoring changes over time. It’s widely used to assess the level of disability in people with MS.


In RMS, the appearance of new symptoms or the aggravation of old ones, lasting at least 24 hours (synonymous with attackrelapseflare-up, or worsening).



See Exacerbation.

Foot Drop

Condition of weakness in the muscles of the leg caused by poor nerve conduction, which interferes with a person's ability to extend the ankle and walk with a normal pattern. The toes touch the ground before the heel, causing the person to trip or lose balance.


List of prescription drugs covered by a health insurance plan that offers prescription drug benefits.



Contrast medium injected prior to magnetic resonance imaging (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 a T1-weighted MRI.


A person who specializes in gastroenterology, a branch of medicine concerned with the structure, functions, diseases, and pathology of the stomach and intestines.


Health Maintenance Organization (HMO)

This type of health insurance plan usually limits care from doctors who work for, or contract with, the HMO. Generally, out-of-network care isn't covered, unless it's an emergency.

High-Deductible Health Plan (HDHP)

This type of plan has a higher deductible than a traditional insurance plan, with lower monthly costs. With an HDHP, you pay more healthcare costs before the insurance company starts to pay its share. An HDHP can be combined with a health savings account (HSA), which allows you to pay for certain medical expenses with money free from federal taxes.


Immune System

An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells.


Ability to resist infection and to heal. The process may involve acquired immunity (the body's 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).


A reduction in immune response. It may be the means by which a drug achieves its intended effect, but it may also be an unintended side effect. For instance, immunosuppression may cause a drop in infection-fighting blood cells.


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


The immunologic response of body tissue to injury, characterized by mobilization of white blood cells and antibodies, swelling, and fluid accumulation.


Prolonged and usually abnormal inability to obtain adequate sleep.

Intramuscular Injection

Injected into the muscle.


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



See Plaque.

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.


A type of white blood cell. Lymphocytes are made in the bone marrow and found in the blood and lymph tissue. The 2 main types of lymphocytes are B lymphocytes and T lymphocytes. B lymphocytes make antibodies, and T lymphocytes help kill tumor cells and help control immune responses.


Lower-than-normal numbers of lymphocytes (a type of white blood cell) result in this condition. It is also called lymphocytic leukopenia and lymphocytopenia.


Magnetic Resonance Imaging (MRI)

Imaging technique based on detection of the response of water molecules to strong magnetic fields. It produces visual images of different body parts without the use of X-rays. MRI allows the neurologist to identify MS lesions in the brain and spinal cord at different stages of their development. T1 scans and T2 scans refer to the different scanning sequences that help distinguish tissue features.

Marcus Gunn Pupil

An abnormal physical examination finding in the pupil of the eye that may result from an episode of optic neuritis.

MRI T1-Weighted Scans

See Magnetic Resonance Imaging.

MRI T2-Weighted Scans

See Magnetic Resonance Imaging.

Multiple Sclerosis (MS)

Presumed autoimmune disease of the central nervous system that is usually first diagnosed in young adults and whose origin is unknown. It damages myelin (nerve fiber insulation) and axons (nerve fibers) in a random and patchy manner, causing a wide range of neurological defects.


Soft, white coating composed of lipids (fats) and protein, surrounding nerve fibers in the central nervous system. A complex natural electrical insulator, myelin serves to speed up the conduction of electrical signals along nerve fibers.



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


Relating to, or involving both, nervous stimulation and endocrine secretion


Psychologist with specialized training in the evaluation of cognitive functions. Neuropsychologists use a number of standardized tests to evaluate specific cognitive functions and identify areas of cognitive impairment. They also may suggest possible treatments for individuals with relapsing MS–related cognitive impairment. See Cognition.


The need to urinate during the night.


Rapid, involuntary movements of the eyes in the horizontal or, occasionally, vertical direction.


Optic Nerve

The main nerve leading from the eye to the brain that transmits visual signals to the brain.

Optic Neuritis

Inflammation or demyelination of the optic (visual) nerve, with temporary or permanent impairment of vision; associated with pain during the acute phase of MS.



An area of inflamed or demyelinated central nervous system tissue.

Point-of-Service (POS) Plans

A type of health insurance plan in which you pay less when you use doctors, hospitals, and other healthcare providers that belong to the plan’s network. In a POS plan, you’re required to get a referral from your primary care doctor to see a specialist.

Preferred Provider Organization (PPO)

A type of health plan that creates a network of participating medical providers, such as hospitals and doctors. You can visit doctors, hospitals, and other providers outside of the network, but you pay less if you use providers within the plan’s network.

Primary-Progressive MS (PPMS)

The clinical course of PPMS is characterized by worsening neurologic function (accumulation of disability) from the onset of symptoms, without early relapses or remissions. PPMS can be further characterized at different points in time as either active (with an occasional relapse and/or evidence of new MRI activity) or not active. It can also be characterized as with progression (evidence of disease worsening on an objective measure of change over time, with or without relapse or new MRI activity) or without progression.

Pseudo Relapse

Temporary aggravation of MS symptoms that have occurred before. Although these relapses can feel like a genuine relapse, they are not a sign of new inflammation within the central nervous system. Usually, symptoms come and go within 24 hours.



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 muscle contraction. Abnormal reflexes can be indicative of neurologic damage, including RMS, and are therefore tested as part of the standard neurological exam.


See Exacerbation.

Relapsing-Remitting MS (RRMS)/Relapsing 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.


Lessening in the severity of symptoms or a “return” to the level of health equal, or similar to, the one experienced prior to the last attack.



Events that may present a risk of harm or injury and/or require medical attention. Safety may be evaluated by laboratory testing, special tests and procedures, and evaluation of patients.


An abnormal condition in which tissue has become hard, produced by overgrowth of fibrous tissue (scars). The term multiple sclerosis refers to multiple scars in the brain.

Secondary-Progressive MS (SPMS)

With SPMS, neurological symptoms worsen progressively. At first, there may still be some relapses; then relapses generally stop completely, and a slow but steady progression of disability takes place.


An involuntary and abnormal contraction of muscle.


Increased muscle tone associated with involuntary muscle contractions, spasms, and stiffness. In MS, spasticity is most prominent in the lower limbs.


See Corticosteroids.

Subcutaneous Injection

Injected under the skin.


Subjectively perceived problem or complaint reported by the patient. In MS, 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 Cells

Any of several types of white blood cells that develop in the thymus gland and play a role in the control of immune response.


Gradual stepping up of a dose of medicine. It allows the body to adjust and become used to the medicine's effects, thereby reducing the likelihood and severity of potential side effects that may occur at the beginning of a treatment.


Tolerability is related to how much you can tolerate the side effects. Sometimes, people can tolerate certain side effects to meet their treatment goals. Other times, side effects can be unbearable, so a change of treatment may be recommended.

Trigeminal Neuralgia

Chronic condition that may cause acute pain in the face caused by demyelination of nerve fibers in the trigeminal nerve root (the nerve responsible for relaying feeling/sensation signals to the brain).