What is a lumbar puncture (LP)?
A lumbar puncture, also known as a spinal tap, involves having a thin needle inserted between two lumbar vertebrae of the lower back to obtain a sample of cerebrospinal fluid (CSF). CSF is the clear fluid that surrounds your brain and spinal cord to protect it from injury.
Why is it done?
The LP is done to help your doctor diagnose central nervous system conditions, such as multiple sclerosis.
How do I prepare?
To prepare for your LP, please be sure to keep in mind the following:
Plan to have someone accompany you to your LP appointment.
Don’t take any NSAID medication (aspirin, naproxen, ibuprofen, Celebrex) 7 days prior to your appointment.
If you are on anticoagulation medication, such as heparin, Coumadin or warfarin, be sure to talk with your doctor about when to stop these medications.
You may be asked to have blood clotting labs (PT, INR) checked within 30 days prior to your appointment.
You should plan to spend 1 hour at your LP appointment. The LP itself only takes about 30 minutes, but preparation and recovery time will take longer. You may need to lie flat for at least 30 minutes following your LP to allow for healing at the site where the needle was inserted.
What happens during the LP?
Your doctor will help you get into a position for the LP. One way of doing this is by lying on your side and drawing your knees to your chest.
Another position for the LP is to sit on a chair, while bending over a pillow. Either of these positions will spread apart the lumbar vertebrae (bones encasing your spinal cord), allowing easier access to the CSF.
Your doctor will then inject a local pain medication (lidocaine) under the skin in an area where the needle will be inserted. This may sting initially.
After this, the LP needle will be inserted between two lumbar vertebrae and the CSF – which will flow freely through the needle – will be collected. About 15 mL of CSF total is collected (equal to 3 tablespoons).
The needle insertion for the LP procedure is similar to the needle insertion for epidural anesthesia used for women during childbirth.
The needle is then removed and a band aid is placed over the insertion site.
You may then be asked to lay flat for around 30 minutes to allow for clotting over the injection site.
An LP may sometimes be done under x-ray guidance. This is called a fluoroscopy-guided LP. If your doctor decides to order this, the LP will be done at the radiology department instead of at our office.
What can I expect after the LP?
After the LP and resting, you’ll be given the tubes of CSF to take to the lab, where a matching blood sample will be drawn. This is done because analysis of CSF is always done along with the analysis of blood drawn about the same time.
After the LP, plan to rest as much as possible for the next 24-48 hours. Limit activities such as driving and heavy lifting.
Are there any risks associated with an LP?
- Post LP Headache: This headache is unique in that it is only present when sitting or standing upright, but disappears when you lie down. Less than 10% of patients experience the post LP headache. If you develop this kind of a headache, you must lie down otherwise, the headache will only get worse. It is a way for your body to tell you that the access point for CSF collection has not healed fully.
Lying flat in bed will help prevent and/or reduce headache pain.
Caffeine also helps decrease the headache (coffee, caffeinated teas, chocolate).
With rest, the headache will usually resolve in 1-2 days.
For pain relief, you can take over-the-counter acetaminophen (Tylenol), but not more than 4,000 mg total in a day.
It may be necessary for a blood patch to be done to stop a headache that doesn’t resolve with these measures.
A blood patch involves drawing a tube of blood and injecting the blood along the path of the LP needle to seal the path. This is done by anesthesia but scheduled by our clinic.
If your headache lasts longer than 1-2 days with no improvement, please call the MS Center at 206-320-2200 for assistance.
- Infection: There is an extremely low risk of infection after an LP procedure
- Bleeding: There is also very low risk of bleeding at the needle insertion site
Do not take an NSAID medication (aspirin, naproxen, ibuprofen, Celebrex) for 1 week after your LP!
Call us immediately or go to the nearest emergency room if you experience any new neurological symptoms other than a headache (weakness, numbness, vision problems, bladder or bowel problems, etc.)