A lumbar puncture (spinal tap) is a common test doctors use to check for signs of MS in your spinal fluid. But a lumbar puncture on its own isn’t enough to confirm an MS diagnosis.

Diagnosing multiple sclerosis (MS) involves several steps. One of the first steps is a general medical evaluation that may include:

  • a physical exam
  • a discussion of any symptoms
  • your medical history

If your doctor suspects that you have MS, you may need to take more tests. This includes a lumbar puncture test, also known as a spinal tap.

A lumbar puncture, or spinal tap, involves testing your spinal fluid for signs of MS. To do so, your doctor will insert a needle into the lower part of your back to remove spinal fluid.

A lumbar puncture is the only way to directly and accurately determine how much inflammation you have in your central nervous system. It also shows the activity of your immune system in these parts of your body, which is important for diagnosing MS.

No special preparation is needed during a spinal tap, but you may want to arrive early to ask any questions you may have about what to expect during the procedure.

During a lumbar puncture, spinal fluid generally is drawn from between your third and fourth lumbar in your lower spine using a spinal needle. Your doctor will ensure that the needle is positioned between your spinal cord and the cord’s covering, or the meninges, when drawing fluid. The whole procedure typically takes 1 hour.

You should expect results to be ready within 2 to 3 days after the procedure.

A spinal tap can tell you whether the amount of protein, white blood cells, or myelin in your spinal fluid is too high. It can also reveal whether the fluid in your spine contains an abnormal level of antibodies.

Analyzing your spinal fluid also can show your doctor whether you might have another condition and not MS. Some viruses can cause signs and symptoms similar to MS.

A lumbar puncture should be given along with other tests to confirm a diagnosis. The procedure can reveal issues with your autoimmune system, but other conditions that affect your nervous system, like lymphoma and Lyme disease, can also show high levels of antibodies and proteins in your spinal fluid, hence the need to confirm a diagnosis with additional tests.

A spinal tap can reveal an abnormal immune response caused by MS. However, other conditions can also cause a similar immune response in the spinal fluid. Also, about 5 to 10 percent of people with confirmed MS don’t show any abnormalities in their spinal tap results.

For these reasons, multiple other testing methods should be used to diagnose MS.

MS shares symptoms with other health problems, so your doctor will need to determine whether it’s MS that’s causing your symptoms and not another condition.

Other tests your doctor might perform to rule out or confirm a diagnosis of MS include:

  • blood tests
  • magnetic resonance imaging (MRI)
  • evoked potential test

MS is often difficult for doctors to diagnose because a spinal tap alone can’t prove whether you have MS. In fact, there’s no single test that can confirm or deny a diagnosis.

Other tests include an MRI to detect lesions on your brain or spinal cord and an evoked potential test to help detect nerve damage.

A lumbar puncture is a common test used to diagnose MS, and it’s a relatively simple test to perform. It’s generally the first step in determining whether you have MS if you’re showing symptoms.

Your doctor will determine whether further tests are needed to confirm a diagnosis.