The MRI and MS: Part III: Relapses in MS
In addition to using MRIs to help diagnosis MS, it is also helpful for a neurologist to see if there are changes on the MRI whenever patients experience symptoms suggestive of a relapse. The most important indicator of active inflammation is the presence of what is known as enhancement.
In almost every MRI ordered in MS patients, the neurologist requests that the patient receive a contrast agent, termed gadolinium. This dye normally stays in the bloodstream and does not enter the brain. If there is a breakdown in the barrier between the brain and the blood vessels in the brain (which occurs when there is active inflammation in MS), the dye can leak into the brain and appear quite bright on the MRI.
In MS, this enhancement typically appears as a ring-shaped lesion, and they can appear in any part of the central nervous system affected by MS—the brain, brainstem/cerebellum, and the spinal cord.
Although most relapses are associated with contrast-enhancing lesions, this is not always the case, and without evidence of such a lesion, it can be quite difficult for both a doctor and patient to determine if the patient is having a relapse or the return of older symptoms.
Alternatively, MRI scans often reveal contrast-enhancing lesions in a patient without new symptoms. These lesions are referred to as “silent lesions.” It may turn out to be the case that if subtle cognitive tests were done, “silent lesions” wouldn’t be so silent after all.
Additionally, I fear that if a patient has a new lesion on their MRI that they don’t feel, they are at high risk of soon having one they will feel. Though I generally try to treat the patient sitting in front of me, rather than the MRI on the computer screen, in some cases of “silent lesions,” I give steroids despite the absence of symptoms to quiet this inflammation.
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