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Occupational therapist (OT)   
Occupational therapists assess functioning in activities of everyday living, including dressing, bathing, grooming, meal preparation, writing, and driving, which are essential for independent living. In making treatment recommendations, the OT addresses (1) fatigue management, (2) upper body strength, movement, and coordination, (3) adaptations to the home and work environment, including both structural changes and specialized equipment for particular activities, and (4) compensatory strategies for impairments in thinking, sensation, or vision.

Oligoclonal bands   
A 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.

A type of cell in the central nervous system that is responsible for making and supporting myelin.

Olmstead Decision
The Supreme Court decision in Olmstead v L.C. (1999) is an interpretation of Title II of the Americans with Disabilities Act (ADA) that affirms the right of people with disabilities to receive services in the most integrated setting appropriate to their needs. The decision recognizes that unnecessary segregation of persons in long-term care facilities constitutes discrimination under the ADA.

Open-label study
A preliminary (Phase I) clinical trial in which all patients receive the experimental treatment.

An instrument designed for examination of the interior of the eye.

Optic atrophy   
A wasting of the optic disc that results from partial or complete degeneration of optic nerve fibers and is associated with a loss of visual acuity.

Optic disc   
The small blind spot on the surface of the retina where cells of the retina converge to form the optic nerve; the only part of the retina that is insensitive to light.

Optic neuritis   
Inflammation or demyelination of the optic (visual) nerve with transient or permanent impairment of vision and occasionally pain.

Also called orthosis; a mechanical appliance such as a leg brace or splint that is specially designed to control, correct, or compensate for impaired limb function.

A person skilled in making mechanical appliances (orthotics) such as leg braces or splints that help to support limb function. See Orthotic.

Continuous, involuntary, and chaotic eye movements that result in a visual disturbance in which objects appear to be jumping or bouncing.

Decalcification of the bones, which can result from the lack of mobility experienced by wheelchair-bound individuals.

Inability to move a part of the body.

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

Paralysis of both lower extremities (legs).

Partial or incomplete paralysis of a part of the body.  

A spontaneously occurring sensation of burning, prickling, tingling, or creeping on the skin that may or may not be associated with any physical findings on neurologic examination.

Paroxysmal spasm   
A sudden, uncontrolled limb contraction that occurs intermittently, lasts for a few moments, and then subsides.

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 one episode to the next. Examples of paroxysmal symptoms include acute episodes of trigeminal neuralgia (sharp facial pain), tonic seizures (intense spasm of limb or limbs on one side of the body), dysarthria (slurred speech often accompanied by loss of balance and coordination), and various paresthesias (sensory disturbances ranging from tingling to severe pain).

See Percutaneous endoscopic gastrostomy.

Percutaneous endoscopic gastrostomy (PEG)   
A PEG is a tube inserted into the stomach through the abdominal wall to provide food or other nutrients when eating by mouth is not possible. The tube is inserted in a bedside procedure using an endoscope to guide the tube through a small abdominal incision. An endoscope is a lighted instrument that allows the doctor to see inside the stomach.

Percutaneous rhizotomy   
An outpatient surgical procedure used in the management of severe, intractable trigeminal neuralgia. The surgeon makes a tiny incision in the side of the person’s face and blocks the function of the trigeminal nerve using laser surgery, cryosurgery (freezing), or cauterization.

Periventricular region   
The area surrounding the four fluid-filled cavities within the brain. MS plaques are commonly found within this region.

Physicians who specialize in physical medicine and rehabilitation, including the diagnosis and management of musculoskeletal injuries and pain syndromes, electrodiagnostic medicine (e.g., electromyography), and rehabilitation of severe impairments, including those caused by neurologic disease or injury. See Electromyography (EMG).

Physical therapist (PT)   
Physical therapists are trained to evaluate and improve movement and function of the body, with particular attention to physical mobility, balance, 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 mobility aids and adaptive equipment.

Pilot study
In clinical trials, an early, small-to-moderate-sized study (also known as Phase II) that follows the Phase I (“safety study”) and is designed to begin determining the effectiveness of the experimental treatment.

An inactive, non-drug compound that is designed to look just like the test drug. It is administered to control group subjects in double-blind clinical trials (in which neither the researchers nor the subjects know who is getting the drug and who is getting the placebo) as a means of assessing the benefits and liabilities of the test drug taken by experimental group subjects.

Placebo effect   
An apparently beneficial result of therapy that occurs because of the patient’s expectation that the therapy will help.

Plantar reflex   
A reflex response obtained by drawing a pointed object along the outer border of the sole of the foot from the heel to the little toe. The normal flexor response is a bunching and downward movement of the toes. An upward movement of the big toe is called an extensor response, or Babinski reflex, which is a sensitive indicator of disease in the brain or spinal cord.

An area of inflamed or demyelinated central nervous system tissue.

Plasma cell   
A lymphocyte-like cell found in the bone marrow, connective tissue, and blood that is involved in the body’s immune system. See also Lymphocyte.

Plasma exchange   
Plasma exchange involves removing blood from the person, mechanically separating the blood cells from the fluid plasma, mixing the blood cells with replacement plasma, and returning the blood mixture to the body. The rationale for plasma exchange is that the plasma contains immune factors that may stimulate disease activity. Substituting replacement plasma may dilute the strength of these potentially destructive immune factors. However, the detailed mechanisms involved are not yet clearly understood.

See plasma exchange.

Position sense   
The ability to tell, with one’s eyes closed, where fingers and toes are in space. Position sense is evaluated during the standard neurologic exam in MS.

Post-void residual test (PVR)   
The PVR test involves passing a catheter into the bladder following urination in order to drain and measure any urine that is left in the bladder after urination is completed. The PVR is a simple but effective technique for diagnosing bladder dysfunction in MS.

Postural tremor   
Rhythmic shaking that occurs when the muscles are tensed to hold an object or stay in a given position.

Power grading   
A measurement of muscle strength used to evaluate weakness or paralysis. Power is tested as part of the standard neurologic exam in MS.

The number of all new and old cases of a disease in a defined population at a particular point in time. The prevalence of MS in the United States at any given time is about 1/750—approximately 400,000 people.

Primary progressive MS   
A 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.

Prediction of the future course of the disease.

Progressive-relapsing MS   
A clinical course of MS that shows disease progression from the beginning, but with clear, acute relapses, with or without full recovery from those relapses along the way.

Prospective memory   
The ability to remember an event or commitment scheduled for the future. Thus, a person who agrees to meet or call someone at a given time on the following day must be able to remember the appointment when the time comes. People with MS-related memory impairment frequently report problems with this type of memory for upcoming appointments.

Pseudo-bulbar affect   
See Affective release.

A temporary aggravation of disease symptoms, resulting from an elevation in body temperature or other stressor (e.g., an infection, severe fatigue, constipation), that disappears once the stressor is removed. A pseudo-exacerbation involves symptom flare-up rather than new disease activity or progression.

Pyramidal tracts   
Motor nerve pathways in the brain and spinal cord that connect nerve cells in the brain to the motor cells located in the cranial, thoracic, and lumbar parts of the spinal cord. Damage to these tracts causes spastic paralysis or weakness.

The presence of pus in the urine, causing it to appear cloudy; indicative of bacterial infection in the urinary tract.

Quad cane   
A cane that has a broad base on four short “feet,” which provide extra stability.

The paralysis of both arms and both legs.

Randomized study
A clinical trial in which all patients are assigned randomly (by chance) to be in experimental group (receiving the experimental treatment) or the control group (receiving the placebo or control substance).

Recent memory   
The ability to remember events, conversations, content of reading material or television programs from a short time ago, i.e., an hour or two ago or last night. People with MS-related memory impairment typically experience greatest difficulty remembering these types of things in the recent past.

An 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 neurologic exam.

Rehabilitation in MS involves the intermittent or ongoing use of multidisciplinary strategies (e.g., physiatry, physical terapy, occupational therapy, speech therapy) to promote functional independence, prevent unnecessary complications, and enhance overall quality of life. It is an active process directed toward helping the person recover and/or maintain the highest possible level of functioning and realize his or her optimal physical, mental, and social potential given any limitations that exist.  Rehabilitation is also an interactive, ongoing process of education and enablement in which people with MS and their care partners are active participants rather than passive recipients.

Relapsing-remitting MS   
A clinical course of MS that is characterized by clearly defined, acute attacks with full or partial recovery and no disease progression between attacks.

A lessening in the severity of symptoms or their temporary disappearance during the course of the illness.

Remote memory   
The ability to remember people or events from the distant past. People with MS tend to experience few, if any, problems with their remote memory.

The repair of damaged myelin. Myelin repair occurs spontaneously in MS but very slowly. Research is currently underway to find a way to speed the healing process.

Residual urine   
Urine that remains in the bladder following urination.

Retrobulbar neuritis   
See Optic neuritis.

Romberg's sign   
The inability to maintain balance in a standing position with feet and legs drawn together and eyes closed.

Reprinted with permission from Rosalind C. Kalb (ed.), Multiple Sclerosis: The Questions You Have—The Answers You Need, 3rd Edition. New York: Demos Medical Publishing, Inc., 2004

  Last updated October 2004