MS and MRI
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. Magnetic resonance imaging (MRI) can reveal telltale scars (lesions) on the brain or spinal cord. There’s no single definitive test for MS. Diagnosis is based on symptoms, clinical evaluation, and a series of diagnostic tests to rule out other conditions. MRI is an important tool in diagnosing MS. It’s also used to monitor disease activity and progression.
What Is a Lesion?
Our nerves have a protective covering called myelin. In MS, the body’s immune system mistakenly attacks myelin, causing inflammation and damage (demyelination). The resulting scar tissue is called a lesion. Some lesions are inactive and don’t cause any symptoms. Active lesions, those that are just forming or expanding, can cause a wide variety of symptoms, depending on where they are located and how big they are. The name “multiple sclerosis” means “multiple scars.”
The Role of MRI in Diagnosing MS
If you have signs and symptoms of MS, your doctor may order an MRI of the brain and spine. MRI allows doctors to see lesions in the central nervous system. It’s important to note, however, that not all lesions are due to MS and not all people with MS have lesions. According to the National MS Society, MRI shows no lesions in five percent of patients with “clinically definite MS” at time of diagnosis. It’s important to note that the number of lesions doesn’t always indicate severity of symptoms.
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. 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.
About 85 percent of MS patients are initially diagnosed with relapsing/remitting MS, according to the National MS Society. In relapsing/remitting MS, distinct inflammatory attacks cause localized damage and accompanying symptoms. The attack eventually subsides, or remits, and symptoms disappear. Each distinct attack is called a relapse. People with all forms of MS can have lesions, but people with relapsing/remitting MS generally have more periods of inflammation. Active areas of inflammation can be seen on an MRI with contrast dye.
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. When relapsing/remitting MS transitions to progressive MS, it’s called secondary-progressive MS.
In primary-progressive MS, the disease is progressive from the start and does not involve distinct inflammatory attacks. Patients generally have more spinal cord lesions than brain lesions. Progressive-relapsing MS begins as a progressive course of disease, but also includes inflammatory attacks.
Active Lesions and Black Holes
MRI with contrast dye can highlight 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 patients if troubling new symptoms appear, or after beginning 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 and/or spinal cord every year.
MRI is noninvasive and doesn’t involve radiation. It uses a powerful magnetic field and radio waves to transmit information to a computer, which translates the data into cross-sectional pictures. Contrast dye, which is injected intravenously, can enhance the data. Lesions show up as white or dark spots, depending on the type of scan. Although the procedure is painless, it makes a lot of noise and requires you to lie very still.
Talk to your doctor about getting an MRI if you begin experiencing MS symptoms.