A spinal tap (also known as lumbar puncture) is one of the tests used to diagnose multiple sclerosis (MS). The test is done in a hospital or clinic setting where a small sample of the cerebrospinal fluid (CSF) is collected, using a thin needle, from the lower lumber region (lower back). A sample that shows abnormal results in proteins and inflammatory cells may indicate MS.
Besides MS, this test is used to confirm conditions such as meningitis, Guillain-Barre syndrome, or brain and spinal cord cancers.
Getting a spinal tap
CSF is clear liquid that acts as a cushion, protecting the brain and the spinal cord. Usually, this fluid is colorless and has the same consistency as water. Nutrients, and substances as well as waste products from the brain, move through cerebrospinal fluid.
Before the test, your may be asked to take a computerized tomography (CT) or a magnetic resonance imaging (MRI) scan to make sure that this test is necessary. Tell your doctor if you’re taking blood-thinning medication (anticoagulants).
You will be asked to wear a hospital gown and likely will be told to lie on your side with your legs pulled up to the chest. The position flexes and spreads the vertebrae, so the doctor can more easily insert a needle between two lower lumbar-region vertebrate. (You will have already be given a local anesthetic to numb the area.) A thin, hollow needle is inserted, passing between vertebrate and through the spinal membrane into the spinal canal.
CSF pressure is measured, and a small fluid sample is collected for analysis, then another measure of fluid pressure is taken. While the needle is in, you may feel some pressure in your back. While the needle is being placed, you may also feel a sudden and brief, sharp pain in a leg, should the needle touch a nerve in the canal.
A bandage will be placed over the site, and you may be told to lie still for a while to reduce the change of post-procedure headaches.
The entire procedure lasts about 45 minutes, and it usually takes less than 2 days for your body to naturally replace lost fluid.