What Are Gadolinium Enhancing Lesions in Multiple Sclerosis?

Contrast will highlight areas of active inflammaton

Nurse explaining MRI results
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For many of you, undergoing MRIs of your brain and/or spinal cord is an accepted part of your MS diagnosis. But even MRIs can be challenging to understand, as there are different types, and some are given with contrast while others are not.

With that, here is a summary of why and how "contrast" (gadolinium) is used in MRIs to diagnosis or monitor multiple sclerosis.

Overview of Gadolinium and Why It's Called "Contrast"

Gadolinium, also called "contrast," is a large, chemical compound that is injected into a person's vein during an MRI scan by a technician.

Gadolinium normally cannot pass from the bloodstream into the brain or spinal cord due to a layer of protection in a person's body called the blood-brain barrier. But during active inflammation within the brain or spinal cord, as during an MS relapse, the blood-brain barrier is disrupted, allowing gadolinium to pass through.

Gadolinium can then enter the brain or spinal cord and leak into an MS lesion, lighting it up and creating a highlighted spot on an MRI. 

Meaning Behind an MS Lesion that "Lights Up"

The purpose of a gadolinium-enhanced magnetic resonance imaging (MRI) scan is to give your doctor an indication of the age of your MS lesions, like whether an MS relapse is happening now or whether one occurred awhile ago.

If a lesion on the MRI lights up, it means that active inflammation has occurred usually within the last two to three months. Active inflammation means that myelin (the fatty sheath that insulates nerve fibers) is being damaged and/or destroyed by a person's immune cells.

If a lesion on an MRI does not light up after gadolinium is injected, then it's likely an older lesion—one that occurred more than 2 to 3 months ago. In other words, the use of contrast helps a neurologist determine the age of a lesion. 

Even so, it's important to understand that an MS lesion seen on an MRI does not necessarily cause symptoms.

These lesions are referred to as "silent" lesions. Likewise, it can be tricky sometimes to correlate a specific symptom with a specific lesion on the brain or spinal cord.

Also, not all lesions represent MS, which is why an MRI cannot be used alone to diagnose or monitor a person's MS. Lesions seen on an MRI can be the result of aging or other health conditions like stroke, trauma, infection, or a migraine. Sometimes, people have one or more lesions on their MRIs, and doctors cannot explain why.

In addition, lesions do interesting things. Sometimes they get inflamed over and over again and eventually form black holes, which represent areas of permanent or severe myelin and axon damage. Research suggests that black holes correlate with a person's MS-related disability. Sometimes lesions heal and repair themselves (and even disappear).

Why Contrast May Be Ordered by Your Neurologist

In the end, your neurologist will likely only order contrast to be given with your MRI if he suspects that your disease is active—meaning you are having a relapse (new or worsening neurological symptoms) or recently had a relapse.

If you are going in for your periodic MRI to determine how your disease is progressing, then contrast is not usually given.

In this case, your doctor will see whether your MRI shows more MS activity, which typically means larger and more lesions.

In this instance, your doctor may suggest changing your disease-modifying treatment, although this is even a bit controversial. Instead, some neurologists prefer to switch a person's medication only if he or she is intolerant of side effects or their symptoms are worsening (basing decisions on the person's overall clinical picture than what their MRI shows).

A Word From Verywell

While it's good to understand your brain and spinal cord MRIs, try not to get too hung up on the number or location of your lesions or spots.

Instead, it's better to focus on improving your symptoms, feeling good, and keeping yourself as happy and healthy as possible. Remain knowledgeable about your disease and the tools used to access it, especially MRIs, which are becoming savvier and thus even more useful.

Sources:

Birnbaum, M.D. George. (2013). Multiple Sclerosis: Clinician’s Guide to Diagnosis and Treatment, 2nd Edition. New York, New York. Oxford University Press.

Giorgio A et al. Relevance of hypointense brain MRI lesions for long-term worsening of clinical disability in relapsing multiple sclerosis. Mult Scler 2014 Feb;20(2):214-9

National MS Society. Magnetic Resonance Imaging.

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