Here is My Question:
I WANTED TO KNOW IF A MRI WITH CONTRAST IS NEEDED TO SEE AND/OR DETECT ACTIVE LESIONS AND PML ACTIVITY. I'VE ONLY HAD ONE MRI DONE WITHOUT CONTRAST. I TRIED LOOKING ON HERE AT PREVIOUS MRI QUESTIONS BUT I COULDN'T FIND A QUESTION SIMILAR TO THIS. THANKS IN ADVANCE!
An active lesion is defined as a new or enlarging non-enhancing lesion or an enhancing lesion. Strictly speaking it is not necessary to use contrast (i.e. gadolinium ) to detect active lesions since all enhancing lesions in MS are associated with a non-enhancing lesion on a non-enhanced study. Contrast can make it easier to identify active lesions, particularly in those people with lots of MS lesions.
The problem with using non-enhanced studies to detect active lesions is the need to compare the image with a prior image done in a similar manner. Since you can only say that the new or enlarging lesion occurred since the last MRI was done, it is difficult to determine when the new lesion occurred. This is why MRIs are often done every 6 to 12 months in people with early relapsing MS.
New MS lesions tend to enhance for only a short period of time (a few days to 4 weeks), so an enhancing lesion is more predictive of very recent activity, unless the unenhanced MRI is obtained at short intervals (e.g., every 1-3 months).
In practice it is usually not that important to know if a new lesion developed in the past month or the past 6 months, if you are using the MRIs to monitor the response to a disease modifying therapy. However, it is important to obtain a baseline MRI after starting the therapy.
Contrast is also not required to detect PML. In fact, most PML does not show enhancement on an MRI scan unless and until your body mounts an immune response to the infection. Diffusion weighted images (particularly DWI trace images) in combination with FLAIR T2 weighted images are most useful for surveillance detection of asymptomatic PML.
Revere P (Rip) Kinkel, MDProfessor of Clinical Neurosciences
Director of the Multiple Sclerosis Program
Clinical Neurosciences Director
University of California San Diego
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