What It Is
A lumbar puncture (also called a spinal tap) is a common medical
test that involves taking a small sample of cerebrospinal fluid
(CSF) for examination. CSF is a clear, colorless liquid that
delivers nutrients and "cushions" the brain and spinal
cord, or central nervous system. In a lumbar puncture, a needle is
carefully inserted into the lower spine to collect the CSF
Why It's Done
Medical personnel perform lumbar punctures and test the
cerebrospinal fluid to detect or rule out suspected diseases or
conditions. CSF testing looks for signs of possible infection by
analyzing the white blood cell count, glucose levels, protein, and
bacteria or abnormal cells that can help identify specific diseases
in the central nervous system.
Most lumbar punctures are done to test for meningitis, but they
also can determine if there is bleeding in the brain, detect
certain conditions affecting the nervous system such as Guillain
BarrÃ© syndrome and multiple sclerosis, and administer chemotherapy
After the procedure is explained to you, you'll be asked to
sign an informed consent form - this states that you understand the
procedure and its risks and give your permission for it to be
The doctor doing the lumbar puncture will know your child's
medical history but might ask additional questions, such as whether
your child is allergic to any medicines.
You might be able to stay in the room with your child during the
procedure, or you can step outside to a waiting area.
A lumbar puncture takes about 30 minutes. The doctor carefully
inserts a thin needle between the bones of the lower spine (below
the spinal cord) to withdraw the fluid sample.
The patient will be positioned with the back curved out so the
spaces between the vertebrae are as wide as possible. This allows
the doctor to easily find the spaces between the lower lumbar bones
(where the needle will be inserted). Older children may be asked to
either sit on an exam table while leaning over with their head on a
pillow or lie on their side. Infants and younger children are
usually positioned on their sides with their knees under their
A small puncture through the skin on the lower back is made and
liquid anesthetic medicine is injected into the tissues beneath the
skin to prevent pain. In many cases, before the injected anesthesia
medication is given, a numbing cream is applied to the skin to
The spinal needle is thin and the length varies according to the
size of the patient. It has a hollow core, and inside the hollow
core is a "stylet," another type of thin needle that acts
kind of like a plug. When the spinal needle is inserted into the
lower lumbar area, the stylet is carefully removed, which allows
the cerebrospinal fluid to drip out into the collection tubes.
After the CSF sample is collected (this usually takes about 5
minutes), the needle is withdrawn and a small bandage is placed on
the site. Collected samples are sent to a lab for analysis and
What to Expect
While some notice a brief pinch and some discomfort, most people
don't consider a lumbar puncture to be painful. Depending on
the doctor's recommendations, your child might have to lie on
his or her back for a few hours after the procedure. Your child
might feel tired and have a mild backache the day after the
Getting the Results
Some results from a lumbar puncture are available within 30 to
60 minutes. However, to look for specific bacteria growing in the
sample, a bacterial culture is sent to the lab and these results
are usually available in 48 hours. If it's determined there
might be an infection, the doctor will start antibiotic treatment
while waiting for the results of the culture.
A lumbar puncture is considered a safe procedure with minimal
risks. Most of the time, there are no complications. In some
instances, a patient may get a headache (it's recommended that
patients lie down for a few hours after the test and drink plenty
of fluids to help prevent headaches). And in rare cases, infection
or bleeding can occur.
Helping Your Child
You can help prepare your child for a lumbar puncture by
explaining that while the test might be uncomfortable, it
shouldn't be painful and won't take long. Also explain the
importance of lying still during the test, and let your child know
that a nurse might hold him or her in place. After the procedure,
make sure your child rests and follow any other instructions the
doctor gives you.
If You Have Questions
It's important to understand any procedure your child
undergoes. If you have questions or concerns about the lumbar
puncture procedure, be sure to speak with your doctor.
Kate M. Cronan, MD
Date reviewed: September 2008
Note: All information is for educational purposes only. For specific medical advice,
diagnoses, and treatment, consult your doctor.
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