My brain has white matter lesions, and i was wondering what they mean. on 8/27, i had an mri that showed no lesions. new findings were found in the second mri on 11/4. why didn't it show up in the first mri? did it go unnoticed? i am 39?

The MRI reading is partially based on the reason why the test was ordered and it is not uncommon that the lesion(s) is (are) more apparent (recognizable) after 2 months in between.

Generically, "white matter lesions" are rather nonspecifc, and can be due to migraine, smoking, head trauma, microvascular angiopathy, a demyelinating disorder, vasculitis/ arteritis, medication reactions, recreational drugs, etc. Ask your regular physicians why there has been a change in the images. MS could present this way?

Did the second reader have access to the first one. It may be that he second machine gets finer details by taking thinner slices. Ask someone to look at them together.