What is multiple sclerosis?
Multiple sclerosis (MS) is a chronic disease that affects the central nervous system (CNS). It causes inflammation and the destruction of myelin. Myelin surrounds nerve fibers and acts like insulation on a wire, preventing "short-circuits" that divert a nerve signal from having its desired effects. The "demyelination" process interferes with nerve impulse transmission, affects muscular control, and causes a variety of sensory, motor, and psychological symptoms. Damage to the myelin usually resolves with time and symptoms subside, but repeated attacks can lead to a continual process of demyelination and remyelination, which produces nerve fiber scarring and progressive disability.
The cause of MS is unknown. It is thought to be an autoimmune process triggered by a virus, environmental factors, and/or a genetic predisposition. Typically, MS first appears and is diagnosed when individuals are between 20 and 50 years of age, although it can occur in young children. It affects women more frequently than men, is more common in Northern European Caucasians than other ethnic groups, and is seen in greater numbers in people who live in temperate climates than warm ones. According to the National Multiple Sclerosis Society, MS affects about 2.1 million people worldwide. It is estimated that about 250,000 to 350,000 people in the U.S. have MS, according to the National Institute on Neurological Disorders and Stroke. The risk of developing this disease is estimated to be about 1 in 750 in the general population. In families with an affected member, the risk rises to 1 in 40, and it is about 1 in 4 for the identical twin of an affected person, strengthening the notion of a genetic component to the cause.
There is no single test that can conclusively diagnose MS. Instead, health practitioners look for a combination of factors to determine if a patient has MS. The factors are described in a document called the "McDonald Criteria," named for the doctor who chaired the 2001 panel of experts charged with establisheding criteria for an accurate diagnosis. The document is updated regularly as new research improves our understanding of the disease. Physicians will consult a patient's medical history and a variety of clinical and laboratory tests to aid in their diagnosis. In applying the criteria for diagnosing MS, a health practitioner must:
- Determine that the CNS has been damaged in at least two places
- Confirm that the damage occurred at separate times, more than one month apart
- Rule out other conditions that cause a similar set of signs and symptoms
Once diagnosed, an individual may be classified as having one of several types of MS, based on signs and symptoms, frequency of relapses, rate of disease progression, and the number of areas that are damaged in the CNS:
- Relapsing-remitting (RRMS)
- Secondary progressive (SPMS)
- Primary progressive (PPMS)
- Progressive-relapsing (PRMS)
Signs and Symptoms
Because MS can attack any area of the central nervous system, the signs and symptoms of MS are many and varied. They are associated with what the nerves in the affected area(s) are responsible for controlling. Symptoms of MS may come and go, and their duration may last from days to months. Some of these include:
- Sensory symptoms such as numbness, tingling, pain, burning, itching, facial pain, and visual disturbances
- Motor symptoms such as speech impediments, weakness, tremor, difficulty walking, lack of coordination, constipation, and problems with the control of urination
- Psychological symptoms such as mood swings, depression, and problems with thinking, learning, and memory
- Fatigue occurs in up to 90% of those with MS.
- Temperature sensitivity occurs in up to 60%; symptoms temporarily worsen with heat.
According to the National Multiple Sclerosis Society, about 85% of those with multiple sclerosis initially have relapsing-remitting MS. They experience periodic attacks or relapses followed by healing and symptom remission. Later in the course of the disease, about half develop secondary-progressive MS. Their symptoms and disabilities worsen as they continue to have relapses but do not fully recover. About 10% of people with MS have a progressive form of the disease. They grow gradually worse without experiencing remissions.
Although there is no single test or set of tests that can establish a diagnosis of multiple sclerosis (MS), there are three tests that are generally considered useful:
- Magnetic resonance imaging (MRI)
- Visual evoked potentials (VEP)
- Cerebrospinal fluid (CSF) analysis
There are no laboratory tests that are completely specific for multiple sclerosis, but several laboratory tests are helpful in diagnosing or excluding this disease as the cause of a person's signs and symptoms. The most useful tests look for evidence of immunoglobulin G (IgG) production within the central nervous system.
- CSF Electrophoresis and Isoelectric Focusing. Electrophoresis and isoelectric focusing are two methods for separating the proteins in a biological fluid. A patient's CSF and serum are evaluated side-by-side on a test surface using either of these two techniques. Following the separation step, a protein stain is applied to both specimens and the banding patterns that appear in the CSF and serum are compared to one another. The presence of two or more IgG bands in CSF that are not present in serum is a positive test for oligoclonal banding. About 90% of people with MS show oligoclonal banding in their CSF.
- CSF Immunoglobulin G (IgG) Index. Increased levels of CSF IgG can be due to excess production of IgG within the central nervous system, which is seen with MS and several other diseases. It can also be due to leakage of plasma proteins into the CSF, such as might occur with inflammation or trauma. To discriminate between these two possibilities, the IgG index is calculated from IgG and albumin measurements performed in CSF and serum:
IgG index = [IgG (CSF) / IgG (serum)] / [Albumin (CSF) /Albumin (serum)]
An elevated IgG index indicates increased production of IgG within the central nervous system. It is found in about 90% of MS cases.
- Myelin basic protein. This is a major component of myelin. Increased concentrations of myelin basic protein in CSF indicate that demyelination is taking place. This process is not specific for MS, as other inflammatory diseases of the central nervous system can also elevate the amount of myelin basic protein in CSF. This test is not widely available; however, it may be used to assess disease activity in cases of established MS.
Health practitioners may also test for diseases that can cause symptoms similar to MS to determine if they may be responsible for a patient's illness. Examples include:
- Lyme disease
- Vitamin B12 deficiency
- Autoimmune disorders (e.g., lupus)
- MRI (magnetic resonance imaging) scans allow doctors to examine the brain. MRI can show both permanent scarring as well as new lesions. These scans are used to help diagnose MS and to track its progression over time. Improvements in MRI technology have significantly improved doctors' ability to accurately diagnose MS at an early stage. Early diagnosis and treatment is key to minimizing the effects of the disease.
In addition to the standard MRI, there are a variety of specialized techniques that may be performed, such as functional MRI, magnetic resonance spectroscopy, and diffusion-tensor MRI. The National Multiple Sclerosis Society (NMSS) web site has more information on the use of MRI in MS.
- Visual evoked potentials (VEP) are electrical diagnostic studies that measure the speed of nerve transmissions (messages) in various parts of the brain. They are recordings of the nervous system's electrical response to visual stimuli. Damage to myelin can slow nervous system response time and VEP tests can reveal evidence of scarring along nerve pathways associated with vision. The NMSS web page has additional details about this test.
Two other types of evoked potentials may be used, though less commonly. Brain stem auditory evoked potentials (BAEP) is a test that helps detect lesions in the brainstem causing delays in the transmission of sounds. Somatosensory evoked potentials (SSEP) is a test that applies a brief electrical stimulus to the wrist or ankle. It detects disruptions in the pathways from the arms and legs to the brain at very specific points of the central nervous system.
There is no cure for multiple sclerosis, but a variety of treatments are available that can reduce the frequency and severity of relapses.
The goals of MS treatment are to slow the progression of the disease, relieve symptoms, and minimize the effects of acute attacks. Health practitioners may prescribe corticosteroids for short periods of time to help reduce the severity of relapses as well as other medications to address specific symptoms, such as beta interferon, copolymer I, natalizumab and fingolimod, the first oral therapy approved by the U.S. Food and Drug Administration for treatment and management of MS symptoms. Fatigue and depression sometimes associated with MS may be treated with appropriate antidepressants or steroidal drugs. For more on specific medications that may be prescribed, see the Treatments page on the National MS Society web site.
MS does not significantly decrease the lifespan of those who have it, but it can frequently and intermittently affect quality of life. People with MS usually work with a team of professionals who help support and monitor their condition and address their changing needs. Current MS research is directed toward understanding the cause of MS in hopes of developing better drugs to treat, if not cure or prevent the disease.
Elsewhere On The Web
Multiple Sclerosis Foundation
The National Multiple Sclerosis Society (NMSS)
National Institute of Neurological Diseases and Stroke: MS Information Page
Multiple Sclerosis Association of America
Multiple Sclerosis Discovery Forum
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
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