What to Expect From a Spinal Tap

Odds are you’ve heard of a spinal tap (aka a lumbar puncture)—but you may not know exactly what it entails. Here's what you need to know.

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Odds are you’ve heard of a spinal tap—but you may not know exactly what it entails. Also called a lumbar puncture, it’s a procedure performed in the lower part of your back to diagnose a health problem, administer medicine, or assist with imaging.

Spinal tapYou may have heard of a spinal tap or lumbar puncture. Here's what it's all about.

During a spinal tap, a doctor or specially trained nurse inserts a needle between your vertebrae to collect cerebrospinal fluid (CSF). This colorless, watery substance cushions your spinal cord and brain, safeguarding them from damage.

When might someone need a spinal tap? Is it dangerous? And what can you expect before, during and after the procedure?

When Do You Need a Spinal Tap?

Spinal taps are often done to help diagnose infections of the central nervous system (CNS). “One of the most common reasons for doing a lumbar puncture is for meningitis,” says Jeff Gadsden, MD, FRCPC, FANZCA, Division Chief of Orthopaedic, Plastic and Regional Anesthesiology at Duke University Medical Center in Durham, North Carolina.

“We’ll take a sample of cerebrospinal fluid,” he explains, “and if we see certain infectious organisms growing in it, that gives us a clue as to how to tailor our antibiotic therapy.”

The procedure can also help providers:

  • Identify certain CNS disorders, such as multiple sclerosis, Guillain-Barré syndrome or epilepsy
  • Diagnose cancers affecting the brain or spinal cord
  • Administer chemotherapy or anesthesia

It can help with imaging, as well. A provider may inject contrast agents (dyes) into the CSF “if they’re trying to get an anatomic view of the spinal cord and the coverings of the spinal cord,” Dr. Gadsden says. It's particularly helpful when a patient can't undergo an MRI. 

A spinal tap can be done in a hospital or outpatient facility, depending on why it’s needed. It’s not an emergency procedure. “We think about emergencies, that brings to mind the sort of things that have to be done within seconds to minutes, and that’s never the case for a lumbar puncture,” Dr. Gadsden explains. “I would characterize it more as an urgent procedure—something that we would want to do in the timeframe of hours rather than minutes.”

How to Prepare for a Spinal Tap

In the days leading up to your spinal tap, follow your provider’s instructions regarding eating and drinking. You may be asked to hold off in the hours beforehand. Tell your healthcare team about any prescription or over-the-counter medications you’re currently taking—especially blood thinners. Let them know about any drug allergies, too.

There is no need to buy special clothing for a spinal tap. “Patients can wear their own clothes” says Dr. Gadsden. “When they show up to the hospital, they’re put into a gown for the procedure.”

The morning of your appointment, call your doctor with any unusual symptoms. If you feel ill, do not go to the hospital without reaching out first. Make sure someone is available to drive you home following your visit, Gadsden suggests, “because sometimes you can feel a bit weak and dizzy afterwards.”

What Happens During a Spinal Tap

A spinal tap is a relatively simple procedure. It typically takes less than 30 minutes to complete.

To begin, you will sit bending forward or lie on your side in a fetal position. “We want your knees pulled up as far as possible and your chin down to your chest so you’re curled up into a little ball,” says Dr. Gadsden. This arcs your back and spaces out your vertebrae, so your doctor has a bigger area to aim for. 

After the skin on your back is cleaned with an antiseptic, a sterile sheet or towels will be placed over you, with an opening over your lower spine. Your doctor will then inject you with a local anesthesia to numb the area. You may feel a stinging sensation, explains Dr. Gadsden, “but then the patient shouldn’t feel the actual spinal needle all that much as it advances between the two bones.”

“Then, the needle itself gets inserted into the skin between the bones in the lower back, and into the spinal space where the cerebrospinal fluid lives,” he continues. In certain situations, an ultrasound or special x-ray imaging technique called fluoroscopy is used to determine the best position for the spinal needle.

Spinal tap illustrationHow a spinal tap is performed

Once the needle is in, the doctor will measure your CSF pressure. At this point, medicine will be administered (if that’s why you’re there) or a sample of CSF will be taken.

“We’ll collect a teaspoonful, usually—it’s all we really need,” Dr. Gadsden says. “And then the needle comes out. Put a little band-aid on the skin and we’re all done.”

Unless your doctor instructs you to move, it is important that you remain still during a spinal tap. “We are trying to advance the needle into a fairly discrete and small area that contains that cerebrospinal fluid,” he says. If you do move, you will likely not be injured, since a spinal tap occurs below where the spinal cord ends. But, he explains, “it helps us to complete the procedure faster and more efficiently if you don’t move.”

Do spinal taps hurt? Spinal tap pain is rare, though sometimes the needle may brush by a nerve root as it’s inserted. “That can feel like a little zing or electric shock down one leg or the other. It’s not a dangerous thing. It’s not anything that went wrong. It’s just that those nerve roots live there,” Dr. Gadsden says.

Spinal Tap Recovery 

Once your spinal tap is finished, you will lie on your back for 30 to 60 minutes so your doctor can look for any adverse effects. Whether you’re allowed to go home depends on the reason for the spinal tap. “If a patient’s coming with an unexplained fever and a concern for meningitis, then they’re probably not a patient we’re going to send home from the hospital,” says Dr. Gadsden.

If your spinal tap was an outpatient procedure, you should be able to leave the facility and resume simple activities after taking a few hours to relax. Pain medication can usually address any discomfort.

Speak with your provider about when you can expect results. “It can be a day up to a week,” says Gadsden. Again, it depends on why you received the spinal tap.

Spinal Tap Risks and Complications

Spinal taps are safe procedures with rare complications. The most common is a headache, which affects 10 to 30 percent of patients and “usually comes on after several hours, sometimes a day or two later,” Gadsden says. “It is not dangerous. It doesn’t lead to any neurologic problems and it’s not unsafe. It’s just literally a headache.”

Drinking water, coffee, tea, or soda may prevent or ease the headache. An over-the-counter pain reliever can help, as well. If it continues after two days, reach out to your doctor, as it could signal a serious problem.

There is a very small possibility of more severe complications following a spinal tap, including infection, bleeding, numbness, and brain herniation (movement of the brain tissue due to pressure). Nerve or spinal cord damage is extremely uncommon.

“The most important thing is to not be afraid of it,” Dr. Gadsden says. “It’s a very safe thing to do. There are very few complications and they’re rare. And most people doing this are careful and gentle and it should not lead to a lot of discomfort or anxiety if done properly.”

Updated on: 06/28/20
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