heya k, it's this: http://en.wikipedia.org/wiki/Epidural_blood_patch
they take some blood and inject it into the site of the LP wound or wounds. when the blood clots it helps close up the leak(s) and normalize the fluid pressure around your brain.
when i had my LP done he started the procedure once but i could still feel what he was doing ... i asked for more freezing so that i just would not be aware of the needle at all.
that request meant that he had to go in twice. that, combined with being told to lie down for only 30 minutes, probably had a lot to do with bringing on the blinding headache from hell.
like i said earlier, once the neuro started talking blood patch, i figured i would just lie on the couch for the weekend and keep the pressure on the leak(s) as low as i could so things could heal. luckily it worked.
i recall, i think, that in some countries they recommend lying down for as much as 8 hours after LP to help prevent the postural headache problem (in case this is not clear, for any newbies, the headache disappears when you lie down and is killer if you sit up or stand).
my results were typical for ms. they said my o-bands indicated chronic inflammation in the CNS and that these would not be caused by my personal history of b12 deficiency. [i later found at least one study where they were present in b12 deficiency. i'm stubborn hehehe]