Many times I get consulted by patients or their relatives when their MRI brain report reads multiple scattered white matter lesions seen. The radiologist's report usually further reads that these can be seen in primary demyelinating conditions like multiple sclerosis or in vascular disorders. Patient's and caregivers are naturally worried when they get this MRI report and do not know what to do and how to proceed further. So I thought that here I shall talk about these white matter abnormalities seen on the MRI. What is their significance? Do they represent evidence of multiple sclerosis?
White matter signal changes on the MRI essentially means that on the MRI, the white matter showed some scattered bright spots. White matter in the brain refers to the fiber tracts that carry information to and fro from the brain.
My first question when somebody asks me what next and what does this mean is to ask them why was the MRI done in the first place. If the MRI was done because there was a clinical suspicion of multiple sclerosis then these white matter lesions may indeed have significance and may represent radiological evidence of MS plaques. Let me explain this with an example. You go to your doctor, you have signs and symptoms that suggest MS (example you may have had an attack of optic neuritis), when the doctor examines you he is able to elict signs in the examination compatible with a diagnosis of MS, then he orders an MRI to see if you do have evidence of white matter lesions in the brain. In a case like this the presence of white matter lesions/ signal changes in the MRI is obviously important. Here it likely does suggest the presence of MS. That said and done I again want to re-emphasize that the diagnosis of MS is made on the basis of clinical history of previous attacks, CSF (spinal fluid) examination and MRI, not just on the basis of the MRI alone. Also there are certain criteria which have to be satisfied on MRI to make a definite diagnosis of MS. These radiological criteria for MS include the number of lesions on the MRI, their location and their size.
Thus it is important to remember that a person who is noted to have white matter lesions on a brain MRI does not necessarily have MS. White matter lesions can be seen in numerous other conditions and they are more commonly seen as we grow older. The thinking behind this is that they represent microvascular ischemic changes in the brain (the smaller caliber blood vessels in the brain showing signs of ischemia or decreased blood flow). Hence these white matter abnormalities on MRI are more commonly seen in patients who have microvascular and macrovascular risk factors such as a history of hypertension, diabetes and high cholesterol (dyslipidemia/ bad lipid profile).
White matter signal changes on MRI may also be seen in patients who have infectious and other inflammatory conditions. They have been reported in the MRI of patients with a history of migraine headaches (migraine too is a vascular disorder and that may explain the connection).
So I want to end by saying that the presence of these white matter signal changes on brain MRI has to be correlated to the history, clinical examination and other ancillary investigations. Your doctor shall help you in going about this in a methodical manner. I repeat these white matter lesions do not suggest MS in each and every case they are found.