The Revised McDonald Criteria sets standards for doctors to use when establishing if a patient has MS. For example, once it required 4 lesions, but now it takes 2.
It shows a list for clinical presentation (medical evidence) and based upon that it provides additional evidence that may or may not be required based upon the clinical presentation.
If you had 1 attack and 1 lesion, your doctor may wait for a second attack or order other tests.
It is like a list of "If A, then B" statements. Based upon the clinical presentation, there are various conditions which might apply before a diagnosis can be made.
Does this help?