An LP (Lumbar Puncture; AKA Spinal Tap) is a procedure in which a needle is placed between two vertebrae of the lumbar (lower back) area of the spine to extract cerebolspinal fluid (CSF). Cerebolspinal fluid is a clear liquid that surrounds the brain and spinal cord (to help cushion the CNS) and is usually extracted for diagnostic purposes, for example; diagnosing Multiple Sclerosis by looking for myelin proteins in the CSF. Fun fact; The CSF that your brain floats in effectively reduces the brain's weight by 97%, which keeps the brain from crushing under it's own weight. (Elaine N Marieb & Katja Hoehn.)
The procedure is pretty simple and though many people may say it is painful I would say it depends on your doctor. My first neurologist sucked at it and hit a nerve so that felt pretty weird. My current neurologist is so good at it I don't feel a single thing, maybe just a minor pinch! So don't let all the hype on the internet scare you.
First they will have you get into a medical gown so they have access to your back. Next they will either have you lay arched on your side or arched over a table sitting up. They will feel around your spine for "the right spot", shoot you up with some local anesthetics (usually 3 shots), and then insert the LP needle that allows your CSF to leak out into a vial. One Bandaid later and your all done!
I have read some articles online that claim that everything I am about to tell you is a myth but this claim is a total load of crap! So, with that being said, the split second they pull that needle out you should lay down (After they place the bandage on of course). My doctor usually has me lay down in the office for about an hour before letting me leave because if you sit up you will most likely get the worst headache you have ever had in your life. Why? Well let's think about it; Your CSF surrounds your brain which maintains a certain pressure in your spinal cord and around your brain. After you take some of this fluid out that pressure now drops because there is less CSF pushing against your brain. By laying down the CSF that is left in your spinal cord and around your brain will spread out and keep things pretty level but if you sit up all the CSF rushes down (thanks to gravity) to the bottom of your spinal cord further reducing the pressure that is (and should) be pushing on your brain.
It is recommended that you lay flat on your back for at least 24 hours after the procedure and drink as much fluid as possible! In adults, there is about 150ml of CSF floating around and that is replaced every 8 hours or so. Drinking fluids helps replace what was taken out. You can pretty much drink anything and beverages with caffeine are said to help prevent a headache. I usually stick to water, coffee, and juice, but mostly water. They say that for every drink you have with caffeine in it you should drink an equal amount of liquid without caffeine.
What is a Blood Patch?
If you do get a headache, in addition to drinking fluids and laying down, regular over the counter (OTC) pain relievers like Ibuprofen may help as well. I have read that around 15% to 50% of patients experience this headache after an LP because the hole that was made in the spinal cord has trouble closing and your CSF continues to leak. If your headache doesn't go away in 24 hours or so you might want to contact your physician who may give you what is called a "blood patch". All this is (basically) is the adding of your own blood into your spinal cord so that it will clot and help plug the hole where your CSF is leaking. I have never had this done but after my first LP I was just about ready to ask for one because I think my headache lasted about a week or so! It was miserable!
So Just Remember...
Lay down, rent a movie, relax, and drink plenty of liquid! After my last LP I drank about 5 water bottles, a cup of coffee, and a lemonade. I laid down for about 24 hours and took it easy the next day not doing anything strenuous like heavy lifting. I had NO HEADACHE and by the day after I was back on track with my life!
Marieb, Elaine N., and Katja Hoehn. Human Anatomy & Physiology. 7th ed. San Francisco: Pearson Benjamin Cummings, 2007. Print.