Although I'm not a physician or scientist. I have heard of this being a factor in the confusion of a diagnosis, so you have to be prepared for the big rejection(s) when it comes to hearing a "non-diagnosis" of what you thought it should have been!
Here's a definition to consider when it comes to a diagnosis for MS especially; Arachnoiditis = is the clumping together and tethering of the descending nerves to the inner lining of the water jacket that contains the fluid that supports brain and the cord in the spinal canal.
As you can see, there are some deeeeep similarities to what MS portrays on an MRI film/data sheet AND it can lead the Neurologist into several different directions, so the key to your question is patience and more patience!
Don't lose sight of this, but also remember that your Neuro is "unchartered" territory as well, so give him/her some space and time.
I hope that helps from a "lay perspective" since I'm NOT a physician, but rather an in depth Reporter of sorts that is here to investigate as much as possible when it comes to our multiple sclerosis and how to move forward!
Take Care for now and remember I'm here for you, jefff