MRI and MS
Multiple sclerosis (MS) is a disease in which the body’s immune system attacks the protective covering surrounding the nerves of the central nervous system (CNS). There’s no single definitive test that can diagnose MS. Diagnosis is based on symptoms, clinical evaluation, and a series of diagnostic tests to rule out other conditions.
Magnetic resonance imaging (MRI) is an important tool in diagnosing MS. It can reveal telltale scars, also called lesions, on the brain or spinal cord. MRI is also used to monitor disease activity and progression.
The role of MRI in diagnosing MS
If you have symptoms of MS, your doctor may order an MRI of your brain and spine. An MRI allows doctors to see lesions in your CNS. Lesions show up as white or dark spots, depending on the type of scan.
MRI is a noninvasive test that doesn’t involve radiation. It uses a powerful magnetic field and radio waves to transmit information to a computer, which translates the information into cross-sectional pictures.
Contrast dye, a substance that’s injected into your vein, can be used to make the MRI images show up more clearly. Although the procedure is painless, the MRI machine makes a lot of noise and you must lie very still for the images to be clear. The test takes about 45 minutes to an hour.
It’s important to note that the number of lesions shown in an MRI doesn’t always indicate severity of symptoms, or even whether you have MS. This is because not all lesions in the CNS are due to MS, and not all people with MS have lesions. According to the National MS Society, MRI shows no lesions in 5 percent of people with “clinically definite MS” at the time of diagnosis.
What MRI can show
MRI with contrast dye can highlight MS disease activity by showing the inflammation of active lesions. Active lesions are those that are new or getting bigger. The contrast images also show areas of permanent damage called “black holes.”
Following a diagnosis of MS, some doctors will use MRI to monitor MS if troubling new symptoms appear, or after the person begins a new treatment. Watching for changes in the brain may help assess current treatment and future options. Some neurologists order a new MRI scan of the brain or spinal cord every year.
MRI and different forms of MS
An MRI will show different things based on the type of MS involved. Your doctor can make diagnostic and treatment decisions based on what your MRI shows.
Clinically isolated syndrome
A single neurologic episode caused by inflammation and lasting at least 24 hours is called clinically isolated syndrome (CIS). You may be considered at high risk of MS if you’ve had CIS and an MRI shows MS-like lesions.
If this is the case, your doctor may consider treating for MS in an effort to delay or prevent a second attack. Someone who has had symptoms but no MRI-detected lesions is considered at lower risk for developing MS than those who have lesions.
People with all forms of MS can have lesions, but people with a type of MS called relapsing-remitting MS generally have periods of inflammation. Active areas of inflammation can be seen on an MRI when contrast dye is used.
In relapsing-remitting MS, distinct inflammatory attacks cause localized damage and accompanying symptoms. Each distinct attack is called a relapse. Each relapse eventually subsides, or remits, with periods of partial or complete recovery that are called remissions.
Progressive forms of MS
Rather than intense bouts of inflammation, progressive forms of MS involve a steady progression of damage. The lesions seen on MRI may be less active than those of relapsing-remitting MS.
There are two progressive forms of MS. Secondary progressive MS occurs when relapsing-remitting MS transitions to progressive MS. And with primary progressive MS, the disease is progressive from the start and does not involve distinct inflammatory attacks.
Talk with your doctor
If you have what you think may be MS symptoms, talk to your doctor. They may suggest that you get an MRI. If they do, keep in mind that this is a painless, noninvasive test that can tell your doctor a lot about whether you have MS and, if you do, what kind you have. Your doctor will explain the procedure to you in detail, but if you have questions, be sure to ask them.