approximately 20 areas of increased t2 signal wm cerebral hemisheres. ?
microvascular chages- migrains, hypertension, vasculitis- VS
demyelinating process - ms.
It is hard to tell - I think you abbreviated? By wm - do you mean white matter?
White matter is a finding that has to be corroborated by other findings and tests as it cannot tell the entire story.
But you listed the possible causes.