I think you need to find another doctor for the NF1. It does not go away.
As for surgery, it depends on the degree. My nephew has done fine healthwise but he had delays in speaking and learning. It varies from person to person.
My 7yr old son was diagnosed with NF1. He just had a mri, and they said it is found on kids w this diagnoses and generally goes away on its own. I on the other hand want 2 know more about it and what will happen if it dont. Does it mean surgery? What does it mean 4 his future. It was found on the learning development part of his brain.
In your tags you put NF1 which is neurofibromatosis (I have a nephew with this) - do you have this diagnosis?
White matter is... ambiguous. Your neurologist needs to do more testing to give you more of an idea. This is better posted under the neurology forum than here as well.