Diane,
I wish you and your son good luck in finding an answer. It can take awhile so be prepared to be patient.
The neurologist may run several different tests. For MS, the tests are to see what it isn't. Rule out any other possible causes and what's left may lead to a diagnosis of MS.
Again, I wish you well. You're certainly welcome to post your questions and concerns. We're here
Take care,
Niko