Hi RD. I have not yet read the replies, so I apologize if I repeat information already posted.
The neurologist said the spinal tap is being done to see what stage Lyme you have? From what I understand, spinal taps show Lyme in less than 5% of cases. I do not believe that Lyme doctors order this test to test for Lyme. If the test is being done to test for Lyme, I highly recommend that you research this further before gettting it done because of how unreliable this test is for Lyme disease.
If you have the test done, make sure you follow all directions for what you need to do after the test. I believe you have to lay flat for a certain length of time or you can get a very severe headache.