What is the likelihood that I have MS?

Here is My Question:
I have had about three MRIs. All of which show that I have white spots on the brain but I was told that they were not where typical white spots would be for MS. I just had a repeat MRI and my neurologist told me today that there were a few new white spots. He said that there were a couple that were where some MS spots would be but he didn't feel that he could diagnosis me with MS based on a few spots. So now I am going for a spinal tap. My question is given the information, what does the likelihood of me having MS look like? I just need to prepare myself. He did say that it would be mild and he felt it would be manageable but I still want to know my odds going into the spinal tap. Any input and advice is greatly appreciated.

Answer:
When MRI is non-diagnostic (i.e., does not fully meet criteria), a spinal tap can be very helpful.

Approximately 90% of patient with multiple sclerosis will have 2 or more oligoclonal bands in that fluid.  This indicates compartmentalized inflammation in the nervous system that is not seen elsewhere in the body (a hallmark of the disease).  The prognostic course of MS cannot really be determined based on spinal fluid analysis.  The procedure itself is simple and can be done in the office.  Rarely, a unique headache can be experienced afterwards that comes on when you sit or stand up but goes away when you lay flat.  If experienced, this usually goes away within the first 24 hours; however, if it lasts longer, another procedure called a blood patch can cure the headache.

A. Scott Nielsen MD MMSc
Neurologist and MS Specialist at Kaiser Permanente