My mother recently had a spinal tap done. After the procedure she started having terrible headaches and nausea. She had to leave work early because of the pain, which is highly unusual as she has worked with migranes in the past. My father was worried and made her go to the doctor where the realized something went wrong during the procedure.
Apparently she was leaking spinal fluid so they had to draw a bunch of blood and inject into the leak to create a blood clot. This helped a trememdous amount and her headaches and nausea went away.
Now I found out that the hospital never ran the tests and when she questioned them they said she needed another spinal tap because her sample had "gone bad". The way my father described my mother's condition after the first procedure I would be surprised if she is willing to go back anytime soon for a second procedure.