A spinal tap, or a lumbar puncture, is a procedure in which a needle is inserted in your lower back to withdraw the cerebrospinal fluid (CSF) — the fluid around your spinal cord. The fluid can be examined in a lab to help diagnose certain health conditions, such as multiple sclerosis and serious infections like meningitis.
A lumbar puncture can also be used to inject an anesthetic, chemotherapy medicine, or dye for a diagnostic test.
What Does a Lumbar Puncture Test For?
During a lumbar puncture test, a sample of your CSF is taken. When this fluid is examined, it can show the number and types of white blood cells, the level of glucose (a sugar), the types and levels of proteins, and whether it contains bacteria, fungi, or abnormal cells.
Doctors may also ask "Is it a normal profile, or is there excess inflammation?” says Justin A. Neira, MD, a spine neurosurgeon at Och Spine at NewYork-Presbyterian Westchester.
The level and presence of certain substances may signal various conditions, including central nervous system disorders that involve your brain, spinal cord, or their coverings (the meninges).
Testing your CSF can help diagnose conditions such as:
- Meningitis (a brain infection)
- Encephalitis (inflammation of brain tissue)
- Cancers such as leukemia
- Bleeding in your brain
- Multiple sclerosis
- Guillain-Barré syndrome
- Alzheimer’s disease and other forms of dementia
Infections within the nervous system, including meningitis and encephalitis, are among the most common reasons for a lumbar puncture, Neira says. Sometimes, meningitis can cause epilepsy. So if you’re having seizures, you may have a lumbar puncture to help figure out what’s causing the seizures, he says.
Other reasons lumbar punctures are used include:
To deliver dyes. While a lumbar puncture is often used to withdraw CSF and test it, your health care provider may also use it to deliver dyes through an injection. If you’re having a myelogram, a type of X-ray diagnostic test that uses contrast dye, a lumbar puncture is used to inject the dye into your spinal column. A myelogram can test for conditions such as herniated disks and arthritis in your spinal joints.
To test pressure and remove extra CSF. If you have pressure in your head, from a condition such as intracranial hypertension or normal pressure hydrocephalus (when CSF builds up in your brain), your doctor may use a lumbar puncture to measure the pressure of your CSF (using a tube called a manometer). Your health care provider can also remove excess CSF during the procedure, which can help relieve the pressure temporarily.
To deliver medications. Doctors sometimes use a lumbar puncture to help treat a condition or to deliver medication into your CSF.
If you need an epidural or spinal anesthetic to block pain in your lower body, you may have a lumbar puncture to deliver anesthesia.
A lumbar puncture may be used to inject medications, including chemotherapy drugs to treat cancer, and muscle relaxants (such as baclofen).
What to Expect During a Lumbar Puncture?
A lumbar puncture is “a minimally invasive diagnostic procedure that can help us figure out the next step in your treatment or rule out things that are concerning,” Neira says.
Before your lumbar puncture, your doctor may order other tests, such as blood tests, an MRI, and a CT scan.
The thought of a needle going into your lower back may sound scary, but “the reality of it is not that bad,” Neira says. “I think that people really fear this needle because it seems so big, but it’s also very, very, very thin,” he says. And the skin where the needle will go will be numb during the lumbar puncture.
Preparing for a lumbar puncture
Before a lumbar puncture, you can maintain your regular eating schedule because there are no dietary or fluid restrictions before the test.
Talk to your doctor about alcohol use and the medications you’re taking. If you’re taking aspirin products or other blood-thinning drugs, they may have you stop taking them or change your medication schedule before the procedure. Tell your doctor if you're allergic to latex or any medications.
Because you can’t drive immediately after getting a lumbar puncture, make plans beforehand for someone to take you home.
Lumbar puncture procedure
During the procedure, you will be asked to lie on your side with your knees drawn as close to your chest as possible and your chin toward your chest. Or you may be told to sit with your arms and head resting on a table.
After your lower back is cleaned with an antiseptic, sterile cloths (called drapes) will be placed around the area. A local anesthetic (pain-relieving medication) will be injected into the area on your back. You may feel a slight burning sensation.
When the area is numb, a thin, hollow needle will be inserted into your lower back between two lumbar vertebrae. The needle will enter your spinal canal to collect fluid or inject medicine. If CSF is collected, it’s usually about three teaspoons.
The lumbar puncture is done at a spot on your lower back that is below where your spinal cord ends, so the needle will not touch your spinal cord during the test. You may feel some discomfort or pressure, but it’s usually not very painful.
“What people experience more is just this feeling of pressure while the needle is going in. And sometimes, once the needle gets into the CSF space, they can feel a little bit of nerve irritation that leads to pain that goes down their leg,” Neira says. “I think it's more of an emotional fear of the procedure than the procedure itself being really painful.”
After the fluid has been removed or medication has been injected, the area will be covered with a small bandage.
If you think this procedure will be difficult for you, talk with your health care provider about it. “If someone knows that they’re going to struggle with this in advance, or we try it and they’re really having a hard time, we can arrange for it to be done in interventional radiology with anesthesia, or we can give people a little bit of sedating medications just to make it a little bit more tolerable,” Neira says.
How long does a lumbar puncture take?
A lumbar puncture can take anywhere from 5 to 30 minutes, depending on your situation, including the anatomy of your spine, Neira says. If you have spinal arthritis or you’ve had a spine fusion, the corridor to get into the spinal canal through the bone is smaller, so it may be trickier to find the precise spot, he says.
In some cases, if that space is narrow, your health care provider may do the lumbar puncture with X-ray, in interventional radiology, Neira says.
Lumbar Puncture Recovery
Usually, it doesn’t take long to recover from a lumbar puncture.
The results of your lumbar puncture test will probably be ready within a couple of days, although some tests may take as long as a week to be completed.
What could go wrong with a lumbar puncture?
“There are some risks to having a lumbar puncture, but they’re pretty rare. And if they happen, most of them are quite manageable,” Neira says.
If CSF leaks from the site where the needle was inserted, it can cause a spinal headache. About 10%-20% of people develop a spinal headache after a lumbar puncture. The headache might get worse when you are sitting or standing. Usually, the headache goes away within 24 hours, as your body replenishes your CSF, Neira says.
The risk of infection from a lumbar puncture is low, and there’s no risk of paralysis.
Occasionally, a small blood vessel can be pierced during a lumbar puncture, causing bloody discharge.; however, no treatment is needed.
Lumbar puncture after care
Once a lumbar puncture is completed, you will be instructed to lie flat. The time you spend lying down after the procedure will vary depending on why you had the procedure. A nurse will discuss post-procedure instructions with you and give you a copy of the instructions.
You shouldn’t drive for 24 hours after having a lumbar puncture. Make sure you have someone else to drive you home from the procedure.
Avoid doing intense or vigorous exercise for a day or so after the lumbar puncture. “Probably the most important thing is not involving yourself in rigorous activity, or activities where you’re going to be bearing down, like heavy lifting,” Neira says. But walking around and going about your daily activities is fine, he says.
If you have a headache, lie down as much as possible and drink plenty of fluids. Contact your health care provider if the headache persists.
Drink 2 1/2 quarts of liquid the day of the spinal tap and the day after (regardless of headache).
How long does it take to recover from a lumbar puncture?
How long it takes you to recover from the procedure depends on your situation and condition. You may be monitored for 15 minutes or for a few hours after a lumbar puncture. If you are getting a lumbar puncture as a diagnostic test for something, but you generally feel well, you may be able to go back to your daily activities shortly after the procedure. But if you have a more advanced medical condition, your recovery may be longer.
If you had a sedating medication before your lumbar puncture, you need to wait for that to wear off before you can leave.
What Are Normal Findings of a Lumbar Puncture?
Your health care provider may be testing your CSF for various things. Normal findings would be levels of white blood cells, glucose, proteins, and other substances that are in normal ranges. If your CSF contains certain bacteria, fungi, or abnormal cells, that would make the findings abnormal.
For example, different bacteria, inflammatory processes, and cancers can lead to different changes that your CSF can show, Neira says. Usually, “bacteria do one thing, whereas viruses do another thing, and tumors do something else.” So a lumbar puncture test can help your health care provider find out more about your condition and what treatment you might need.
When to Contact the Doctor After a Lumbar Puncture
After your lumbar puncture, call your local doctor immediately if:
- You notice any unusual drainage, including bloody discharge, at the puncture site.
- You develop a fever.
- Your headache persists.
- Your pain symptoms worsen.
Takeaways
A lumbar puncture is a routine procedure that uses a needle either to withdraw some of your CSF or inject a medication or dye. A hollow, thin needle is inserted into your lower back, and it’s usually not painful. With a lumbar puncture test, the CSF that’s withdrawn will be tested in a lab for different substances that can signal certain medical conditions. It can help your doctor diagnose you.
Lumbar Puncture (Spinal Tap) FAQs
Are you put to sleep for a lumbar puncture?
No. Typically, a health care provider gives you a local anesthetic to numb the area, but you are not given a general anesthetic to make you unconscious.
How long are you on bed rest after a lumbar puncture?
Usually, you don’t have to be on bed rest after a lumbar puncture. You just have to take it easy and avoid intense activities.
Does a lumbar puncture hurt?
Although you might feel pressure or discomfort during a lumbar puncture, it’s not usually painful.
Can I lay on my side after a lumbar puncture?
Yes. After a lumbar puncture, you can lie on your side or in any lying-down position.
