Multiple sclerosis is a chronic health condition that damages myelin, which is a protective covering in a person's brain and spinal cord. As a result, communications from the brain to the spinal cord cannot take place.
Symptoms of multiple sclerosis (MS) can vary from person to person. The disease is a progressive one, so the symptoms will often worsen over time. Examples of symptoms associated with MS include vision problems, bowel and bladder function disorders, difficulty walking, fatigue, and weakness or numbness in the body.
Doctors do not know what causes MS, nor is there a cure for it at this time. No single test exists that can help a doctor definitively diagnose MS. However, imaging tests to more closely examine the brain and spinal cord are often used to identify any damage that may indicate MS. Imaging tests are also used to track the progression of the disease over time.
Contents of this article:
Role of radiology in an MS diagnosis
An MRI scan may be the best way to view portions of the central nervous system.
When a person has MS, the condition can cause small areas of scarring or damage in the brain and spinal cord known as lesions.
Radiology tests can help doctors identify these lesions, which could confirm an MS diagnosis. Before a diagnosis of MS can be made, a doctor must identify the following:
- Indicators of lesions or damage in at least two areas of the brain, spinal cord, or optic nerves
- Indicators that the damage to the two lesions has taken place at least 1 month apart
A doctor will also carry out other tests in order to rule out the possibility that the symptoms are not caused by other conditions. Conditions that can sometimes resemble MS include severe vitamin B12 deficiency, collagen-vascular disease, and Guillain-Barré syndrome.
A person can experience MS-like damage one time but never have further damage. This is known as clinically isolated syndrome. To diagnose a person with MS, a doctor must identify lesions that occurred at least 1 month apart. The appearance of the lesions can usually indicate that one is older than another.
What radiology tests aid in an MS diagnosis?
Magnetic resonance imaging (MRI) testing is an imaging test that uses a magnetic field as well as radio waves to create an image by measuring the water content in tissues. Unlike computed tomography (CT) or X-ray scans, an MRI doesn't involve radiation exposure.
According to the National MS Society, MRI is the most sensitive, noninvasive way to view portions of the central nervous system. It is also the "preferred imaging method" for diagnosing MS and monitoring the disease's progression.
An MRI is useful to doctors because myelin, the substance that is destroyed by MS, is made of fatty tissue. Fat is like oil in that it repels water. An MRI measures water content, so areas where myelin is damaged will show up more clearly. On an imaging scan, damaged areas may appear white or darker, depending on the type of MRI scanner.
Different MRI scanner types are available. Ideally, a person should always have their scans done on the same type of scanner so that a doctor can make the best comparisons between the images. Examples of MRI scanner types used to diagnose MS include:
- T1-weighted: This scan involves injecting a person with a material known as gadolinium. Usually, gadolinium's particles are so large that they don't go through parts of the brain. However, if a person has damage in the brain, the particles will highlight the damaged area. A T1-weighted scan will cause lesions to appear dark and help a doctor identify them more easily.
- T2-weighted: T2-weighted images involve administering different pulses via the MRI machine. Older lesions will appear in a different color to newer lesions. Usually, lesions are lighter and bright on T2-weighted images as opposed to T1-weighted scans where they appear darker in color.
- Fluid attenuated inversion recovery (FLAIR): FLAIR images use a different sequence of pulses from T1 and T2 imaging. These images are very sensitive to brain lesions that MS usually causes.
- Spinal cord imaging: Using an MRI to show the spinal cord can help a doctor identify lesions that occur in the brain as well as spinal cord, which is important in making an MS diagnosis.
Some people may be at risk from an allergic reaction to the gadolinium used in T1-weighted scans. There is also a risk that the substance can cause kidney damage, especially in people who already have some decreased kidney function.
Regardless of the testing type, an MRI scan is a painless test. However, generating the magnetic field can be very loud. The noises can sound like tapping and thumping. A person is often given earplugs to reduce the noise.
Also, people who are claustrophobic may have difficulty being inside the tube-like MRI. MRI machines that are "open" and do not have the tunnel, do not always produce such high-quality images. Therefore, most doctors recommend the tunnel-like MRI for MS detection. Sometimes doctors will administer medications before the test to help reduce anxiety from claustrophobia. The MRI test can last anywhere from 15 minutes to an hour or more.
After the test, a person can usually return to their everyday activities. If they did receive sedation medications, they may need help from another person to help them get home.
What do radiology test results mean?
MRI scans can help in diagnosing MS but they may not always be conclusive.
A radiologist who specializes in interpreting images will analyze the results of any MRI scans. These results will be sent to a person's doctor for further interpretation.
While MRI tests are extremely helpful in diagnosing MS, they are not the only tests a doctor will use. According to the National MS Society, an estimated 5 percent of people with MS do not have lesions that appear on an MRI.
Also, aging can cause people to develop small lesions on the brain that are not related to MS. This is especially true for people older than 50 years. While doctors can still use MRI to try to establish whether someone over 50 years has MS, diagnosis may be more difficult.
Additional testing for MS
Doctors may use other tests in addition to radiology exams for diagnosing MS. One example is a cerebrospinal fluid (CSF) evaluation. This involves inserting a needle into the spinal canal and withdrawing CSF. The presence of certain antibodies in the CSF can indicate that a person may have MS.
Evoked potential tests are another test doctors may use for MS. These tests measure how a person's brain responds to certain stimuli. Examples of the stimuli could include flashing lights or electrical impulses applied to the legs or arms. This test is beneficial for diagnosing MS because it allows a doctor to detect how effectively and quickly a neurological impulse travels.
Living with MS
If a person has been diagnosed with MS, a doctor is likely to continue using MRI scans to help them decide on the best treatment methods, and to determine the disease's progression. For example, if a doctor has prescribed a particular treatment designed to prevent MS symptoms from worsening, yet an MRI shows that lesions are more pronounced, a different treatment may be needed.
There are different types of MS. Some types of MS may respond to medications known as disease-modifying therapies. Designed to slow the progression of MS, these medications include beta interferons, glatiramer acetate, and dimethyl fumarate. Other medications, such as corticosteroids, can reduce inflammation in the nerves. All of these medications may have side effects, so anybody considering these medications should discuss them with a doctor.
Some other medications to treat MS focus on reducing symptoms but not treating the underlying MS. Examples include medications to treat fatigue, improve bowel and bladder dysfunction, and reduce depression.
Physical therapy exercises can also improve mobility when a person has MS.
Some common early signs associated with MS include vision loss, difficulty maintaining balance, numbness or tingling, and difficulty tolerating heat. If a person experiences these symptoms, they should see their doctor for further investigation.