Understanding Your MRI in Multiple Sclerosis

MRI in Diagnosis and Monitoring of MS

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A magnetic resonance imaging test, or MRI, is the most widely used test in diagnosing and monitoring multiple sclerosis (MS). The good news is that over the years, these non-invasive imaging tests have become even more precise and targeted, allowing MS to be diagnosed sooner that ever before.

How MRIs Are Utilized in MS

There are three main reasons how MRIs are used in the evaluation of MS:

Diagnose

MRIs of the brain, spinal cord, and optic nerve (which comprise the central nervous system) are the most powerful, sensitive tools for diagnosing MS. Specifically, an MRI can detect lesions, which are indicative of an MS relapse. Although, keep in mind, about five percent of people with MS have normal MRIs (no lesions) at the time of diagnosis.

Track Disease Progression

MRIs are used to track MS disease progression. These sophisticated imaging tests provide doctors with an indication of how well a person is responding to their MS disease-modifying therapy. In addition, MRIs help neurologists determine whether a person's MS is transforming from relapsing-remitting MS into secondary progressive MS.

While the timing varies, many neurologists recommend follow-up MRIs every year or so to monitor a person's disease course and determine whether a new disease-modifying medication needs to be considered.

Detect a Relapse

A person may undergo an MRI of their brain and/or spinal cord if they are developing new neurological symptoms, indicating a potential MS relapse. Lesions that "light up," with a contrast material called gadolinium indicate active inflammation within the central nervous system. On the other hand, a if a lesion on an MRI does not light up with gadolinium, then it's likely this lesion is one that occurred at least two to three months prior.

Types of MRIs

The two types of MRIs used to understand a person's multiple sclerosis are the T1-weighted and T-2 weighted scans. 

T1-Weighted MRI

A T1-weighted magnetic resonance imaging (MRI) scan shows hypointense lesions, also referred to as “black holes,” because they appear dark on the images. These "black holes" may represent areas of permanent myelin and axonal damage or loss, especially if they are very dark. In other words, the darker the spot, the more damage has been done.

When myelin and axons are damaged or destroyed, nerve cells cannot communicate to each other efficiently or at all—this is what causes a person's unique MS symptoms. 

It's important to note that in addition to permanent axonal loss, a "black hole" or T1-weighted lesion may represent areas of edema, or swelling, which are temporary and disappear on subsequent scans. This is why a neurologist will often compare your current MRI with old MRIs—to see if lesions have resolved.

T2-Weighted MRI

The T2-weighted magnetic resonance imaging (MRI) scan shows the total number of MS lesions. This a good indication of a person's MS disease burden over the prior year. The MS lesions on a T2-weight MRI show up as hyperintense lesions, or "bright spots" and are often referred to as plaques. If plaques continue to become re-inflamed, they may eventually turn into "black holes." That being said, sometimes plaques can heal, repair themselves, and disappear.

Receiving Contrast During a MRI

While a person is undergoing a MRI, the MRI technician may give them a contrast through their vein called gadolinium. If gadolinium enters a MS lesion on an MRI, it will light up. A lesion that lights up indicates an area of active MS-related inflammation, meaning demyelination has occurred within the last two or three months.

A Word From Verywell

It's important to understand that while an MRI is a key diagnostic and MS treatment accessing tool, interpreting an MRI requires careful thought. This is because lesions on MRI do not always perfectly correlate with a person's symptoms. For example, an MRI may reveal lesions that do not cause any symptoms for a person (called "silent lesions."). Furthermore, small lesions on an MRI may occur naturally as part of the aging process, and so are not necessarily related to a person's disease.

This is why a neurologist tends to focus on how a person feels and functions in their everyday life. In other words, your neurologist will hopefully treat your symptoms, using your MRI results as a guide in your care, and not the sole dictator.

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