The types of MRI used – most commonly T1- and T2-weighted scans – measure resonance in different ways.
Because the layer of myelin that protects the nerve cells is fatty, it repels water. In the areas where myelin has been damaged by MS, the area holds more water and shows up on an MRI as either a bright spot or a darkened area depending on the type of scan that is used. A contrast agent, gadolinium, can be injected into a patient intravenously to further enhance the sensitivity of a T1-weighted MRI scan.
T1-weighted scans show dark areas that are thought to indicate areas of permanent nerve damage.
The image shows T1-weighted MRI scans of the brain of a person with MS. The arrows point to the black holes.
T1-weighted scans enhanced with gadolinium (injected by IV to further enhance scan sensitivity) supply information about current disease activity by highlighting areas of active inflammation. These areas of inflammation appear as active lesions, meaning that they are new or getting bigger.
Gadolinium-enhanced T1-weighted scan
The image shows a gadolinium-enhanced MRI scan of the brain of a person with MS. The arrow points to the lesion.
T2-weighted images provide information about disease burden or lesion load (meaning the total amount of lesion area, both old and new).
The image shows a T2-weighted MRI scan of the brain of a person with MS. The arrow points to the lesion.
Once a diagnosis of MS has been clearly established, no additional MRI scans are needed for diagnostic purposes.
But they remain important tools for tracking the progress of the disease and making treatment decisions. For example, a neurologist may consider disease activity on an MRI as well as a person’s clinical symptoms and relapses in order to determine whether the current treatment is effective or a change in treatment needs to be considered.
Talk to your doctor about how often you can expect to have an MRI.
MRI can be used to take pictures of the brain and spinal cord in many different directions (or planes).