Hi strizzlow,
I did have a Lumbar Puncture(LP) many years ago. My LP was positive and I received a diagnosis of MS.
There is a criteria for diagnosing MS --- The McDonald Criteria. A positive LP can help support a diagnosis of MS but by itself will not give you a diagnosis of MS. The LP is used in testing of other conditions as well as MS.
Information about a LP:
http://www.nlm.nih.gov/medlineplus/e...cle/003428.htm