Spinal tap (Lumbar puncture)
We understand that you may have a lot of questions when you learn that your child needs a lumbar puncture:
- What is it?
- Will my child need to be hospitalized?
- Why does my child need it?
- Will it hurt?
We’ve tried to provide some answers to those questions here, and your child’s doctor can talk more about the test with you when you meet.
Background on the brain and spinal cord – the central nervous system (CNS)
Your child’s central nervous system (CNS) made up of her brain and her spinal cord. It’s responsible from collecting information from and sending information to all parts of her body.
The spinal cord is a long, thin bundle of tissues and cells that extends downward from her brain. It’s nestled in the spinal canal and protected by the vertebrae, just as the brain is protected by the skull.
In the vertebrae, bones are stacked on top of one another and connected by joints, for flexibility. In between are disks that provide cushioning. The disks also create little spaces between the bones, spaces that are covered by a thin membrane. When we perform a lumbar puncture, we go through that thin membrane to get to the spinal canal.
The brain and the spinal cord are also bathed in (and protected by) a fluid produced in the brain called cerebrospinal fluid. This fluid can be useful in diagnosing a condition your child may have.
What is a lumbar puncture?
A lumbar puncture is a common procedure in which we ask your child to curl up in a ball, and then we use a special needle to gain access to her spinal canal through her back. This lets us remove a bit of fluid for testing, deliver medications or measure/relieve pressure in her spinal canal. This sounds invasive and painful, but while it may feel uncomfortable and some children have headaches afterwards, it feels more like a pinch that lasts a few minutes. Most children have lumbar punctures with local anaesthesia, meaning that they’re alert, but the area of the puncture is extremely numb.
Why would my child need a lumbar puncture?
Your child’s doctor might request a lumbar puncture in order to:
- take a sample of the cerebrospinal fluid so that it can be examined in a lab
- inject medication (such as anesthesia or chemotherapeutic agents) directly into the CSF, so her body can use it most effectively
- remove excess cerebrospinal fluid (decreasing spinal canal pressure) in children with hydrocephalus or intracranial hypertension
- measure the amount of cerebrospinal fluid pressure in the spinal cord
If your child’s nervous system is damaged, it can cause delays in her normal development and functioning. Early detection means that we have a better chance of identifying the cause, can treat her quickly and decrease the chance of long-term complications.
What conditions are associated with lumbar punctures?
Conditions most commonly associated with lumbar punctures include:
- infections such as meningitis (bacterial, viral, parasitic or fungal)
- other cancers of the brain or brain system.
- inflammation of the blood vessels (vasculitis)
- auto-immune disorders such as multiple sclerosis
How do we prepare for a lumbar puncture?
Most often, no special preparation is needed. If your child will have the procedure under sedation, her doctor will give you some preparation guidelines to follow.
Before coming to the hospital, explain to your child what will happen during the test and encourage her to ask questions and express her feelings.
Will my child be under sedation?
Most children have lumbar punctures with local anaesthesiameaning that they’re alert, but the area of the puncture is extremely numb. Sometimes, we use intravenous (IV) sedation, which makes your child very sleepy. On rare occasions, the procedure is done under general anesthesia, in an operating room. You and your child’s doctors will decide together what is best for your child.
What happens during the procedure?
1. Once your child is ready for the test, we’ll have her lie on her side and curl up in a tight ballso the physician can access her lower back. A technician or nurse stand beside your child to help her hold still and explain what the physician is doing. Remaining still is very important and will make the test go more smoothly.
2. We feel your child's back for a space between the bones of the lower part of the spine to insert the needle. He or she will clean the spot with a special solution, and then apply a numbing cream to your child’s skin.
3. We further numb the spot by injecting a special medication. This stings for a few seconds, but it makes the spinal tap less painful. Then, we put the special needle through the numbed skin, and into the space where the CSF is found.
4. Your child feels some pressure while the needle is being pushed in. It's important she stays still during this time. The cerebrospinal fluid will begin to drip out of the needle and a small amount will be collected in test tubes. We also measure the pressure in her spinal canal.
5. If we need to inject medication in the spinal canal, we give it through the same needle after the cerebrospinal fluid is collected.
6. We remove the needle and clean and bandage the area on your child’s back.
How does a spinal tap measure pressure?
After the needle is inserted, the doctor attaches a hub with a three-way valve. One opening is connected to a manometer (a little tube that measures pressure). Cerebrospinal fluid rises up the manometer just like mercury or water rises up a barometer in response to atmospheric pressure, and can be measured that way.
How long does a lumbar puncture take?
About 30 minutes. We also ask that your child lie down immediately afterwards here at the hospital for several hours before going home. Please be assured that during and after the test, we do everything we can to make sure she’s as comfortable as possible.
Where will it take place?
Lumbar punctures usually take place in a doctor’s office – most often a neurologist – that has been equipped to do this procedure.
Who will be in the room with my child during the procedure?
Your child will be with her doctor or nurse practitioner performing the lumbar puncture, and a nurse or clinical assistant who will help. There may be another doctor in to assist or supervise, too. And parents are always invited to stay, if they think it will be helpful for their child to have them there.
What happens after the test?
After the test, your child will lie down immediately afterwards here at the hospital for several hours before going home. You can read to your child or play quietly with her while she is in bed, and encourage her to drink lots of fluid.
Is there anything special my child should do when we get home?
We recommend rest and quiet activities for 24 hours. If your child has a headache, which is fairly common, have her drink lots of fluids and lie down for a few hours.
Are there any signs I should watch out for once my child is brought home?
Most children do very well after a lumbar puncture, but contact your child’s doctor if:
- her headache persists into the next day, and she has been taking it easy and drinking a lot of fluids
you notice (or your child complains of) anything that may be a neurological concern, such as:
- changes in vision
- unsteadiness on her feet
- significant discomfort at the site of the puncture
- changes in sensation in her legs
When will we get the results of the test?
This all depends on which tests the lab(s) run. Simple tests are ready the same day, if not within a few hours. If we’re looking for bacteria, we’ll know the results within 72 hours. Other, more demanding tests may be ready in a matter of days or weeks; and specific biochemical tests that are looking for certain antibodies may take six to eight weeks to come back.
Once the results are in, your child’s doctor will explain the lab report to you, and then you’ll discuss next steps together.
Q: Does it hurt?
A: We will give your child local numbing medication, so your child won’t feel anything as the needle goes in and out. Sometimes children have an electrical sensation in the leg, which shouldn’t last. Your child’s muscles may feel a little crampy as have her curl up in a tight ball, but that goes away, too.
Q: Could my child be paralyzed from this?
A: No. Lumbar punctures are done in an area of your child’s body that’s below the spinal cord, so there’s no risk of accidentally contacting it.
Q: How long does it take?
A: The procedure takes about 30 minutes, but we ask that your child lie down here at the hospital for a few hours afterwards.
Q: Are there any risks or complications?
A: As with many medical procedures, there’s a risk of infection or bleeding. But we’re very careful, and the risk of infection here at Children’s is extraordinarily low.
Q: When will we know the results?
A: It depends on the tests – it could be a matter of hours for routine tests, and six to eight weeks for some more in-depth tests.
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