How Does a Spinal Tap Help Diagnose MS?
The results of the procedure can help doctors see whether your body’s immune system is attacking itself, which is what happens in multiple sclerosis. If you have the condition, your CSF (spinal fluid) will have higher amounts of certain proteins.
If someone’s CSF doesn’t have these proteins, though, they might still have multiple sclerosis -- 5% to 10% of people with the condition never show signs in their spinal fluid.
Also, these signs can show up in a number of other diseases, too. So a spinal tap by itself can't confirm or rule out a diagnosis of multiple sclerosis. It must be part of the total picture of testing for the disease.
How Do I Prepare for a Spinal Tap?
You don’t have to do anything to get ready, unless your doctor gives you special instructions.
What Happens During a Spinal Tap?
To start, you’ll lie on your side with your knees drawn as close to your chest as possible. Or you'll sit with your arms and head resting on a table.
After the skin around your lower back is cleansed and covered, you’ll get medicine to numb that part of your body. Your doctor will put a long, thin hollow needle in your low back between two bones in your lower spine and into the space filled with CSF. He’ll take 1-2 tablespoons of fluid and remove the needle. The procedure doesn’t touch your spinal cord.
What Happens Afterward?
Avoid intense exercise for a day or so after the procedure.
Is a Spinal Tap Safe?
Yes. But just like most tests, there are a few minor risks. These include:
- Headache. About 10% of people get a spinal headache -- one that gets worse when you sit or stand and feels better instantly when you lie down. If you get one, lie down as much as possible and drink plenty of fluids.
- Infection. But the risk is very low.
- Bloody tap. Sometimes the procedure may pierce a small blood vessel, so blood mixes in with the CSF. You won’t need treatment for it, but in some cases, you may need another spinal tap later on to get a "clear" sample.
Call your doctor right away if you notice any unusual drainage, including bloody discharge, or pain that gets worse.