A spinal tap (lumbar puncture) is a test that checks the health of the cerebrospinal fluid (CSF). CSF is a fluid that surrounds the brain and spinal cord. The test also measures the pressure in the spinal canal. The doctor does a spinal tap by putting a needle into the lower back area. They remove a small sample of CSF from the spinal canal to be tested in a lab. The test does not damage the spinal cord or nerves. In some cases, your child's doctor may need to use a special X-ray to help with the procedure. Within a few hours, your child's body will make new fluid to replace what is removed. The test usually takes about 10 to 15 minutes.

A spinal tap may be done for many reasons. It may be done to diagnose problems, such as:

• Meningitis. This is an inflammation of the membrane covering the brain and spinal cord. The inflammation is usually caused by a viral, bacterial, or fungal infection.
• Encephalitis. This is an inflammation of the brain that is usually caused by a virus.
• Certain cancers. These are cancers of the brain and spinal cord.
• Subarachnoid bleeding. The test can look for bleeding in the area between the brain and the tissues that cover it. This is called the subarachnoid space.
• Reye syndrome. This is a disease that causes severe problems with the brain and other organs.
• Myelitis. This is an inflammation of the spinal cord.
• Guillain-Barré syndrome. This is a disorder in which the body's immune system attacks part of the nervous system.
• Demyelinating diseases. These diseases attack the protective coating that surrounds certain nerve fibers. The diseases include multiple sclerosis and acute demyelination polyneuropathy.
• Headaches of unknown cause. A spinal tap may be done to diagnose inflammatory conditions that can cause a headache.
• Pseudotumor cerebri. This is also called idiopathic intracranial hypertension. This condition causes pressure in the subarachnoid space to increase.

A spinal tap may be used to measure the pressure of the CSF. To do this, the doctor uses a special tube called a manometer.

A spinal tap may also be done to inject medicine directly into the spinal cord and central nervous system. These medicines include:

• Spinal anesthesia medicines before surgery.
• Contrast dye for X-ray studies, such as myelography.
• Chemotherapy medicines used to treat cancer.

Your child's doctor may have other reasons to recommend a spinal tap.

Most medical procedures have some risks. Risks of a spinal tap include:

• Broken blood vessels. It's possible to break a small blood vessel near the skin during the procedure. There may be bruising. This is not a serious condition. It will go away on its own.
• Infection. Skin bacteria can infect the puncture site and spinal fluid. To help prevent this, your child's skin is cleaned with an antiseptic solution. Only sterilized equipment is used.
• A headache that gets worse. The spinal tap may cause a headache. Or it can cause an existing headache to get worse. This may happen if spinal fluid leaks internally from the puncture in the spinal canal. When your child gets home, have them lie flat, rest, and drink fluids. This may help ease a headache if it occurs.
• Bleeding. There is a small risk of minor bleeding where the needle is put through the skin. This bleeding usually stops with mild pressure by the doctor. In rare cases, there is also a small risk of bleeding around the spinal canal.
• Back pain. Your child may have back pain, usually where the needle is inserted. This can happen after the procedure. This usually goes away after 1 to 2 days. You can treat it with an over-the-counter pain medicine.
• Brain damage. In rare cases, brain herniation can happen if this procedure is done while there is swelling in the brain. Herniation means that part of the brain is squeezed (compressed) and damaged because of swelling in the brain. The doctor will make sure your child has no brain swelling before doing a spinal tap.

Ask your child's doctor about the risks and benefits of this test for your child.

Follow all directions given by the doctor to prepare your child for the test.

If anesthesia will be used during the test, your child may not eat or drink for a certain number of hours before the test. Follow any directions your child is given for not eating or drinking before the test.

Tell your child's doctor:

• What medicines your child takes, both prescription and over-the-counter medicines.
• If your child takes any medicines that thin the blood, such as aspirin or warfarin.
• What vitamins, herbs, and other supplements your child takes.
• If your child has any health problems, especially a history of seizures or a blood clotting disorder.
• Is allergic to any medicines or iodine.

Many hospitals have people trained in helping children cope with their medical care or hospital experience. These people are often called child life specialists. Check with your child's doctor if child life programs or other similar services are available for your child. You can also do certain things to help them get ready for a test or procedure. How best to do this depends on their needs. Start with the tips below:

• Use brief and simple terms to describe the test to your child and why it's being done. Younger children tend to have a short attention span, so do this shortly before the test. Older children can be given more time to understand the test in advance.
• Tell your child what to expect in the hospital during the test. For instance, you could mention who will be doing the test and what the hospital room will look like.
• Check that your child understands which body parts will be involved in the test.
• As best you can, describe how the test will feel. For instance, if your child is awake during the test, they may feel some discomfort or pressure when the needle is inserted. Reassure your child that this discomfort won't last long.
• Let your child ask questions and answer these questions truthfully. Your child may feel nervous or afraid. They may even cry. Let your child know that you'll be nearby during the test.
• Use play when telling your child about the test. With younger children, this can involve role-playing with a child's favorite toy or object. With older children, it may help to read books or show pictures of what happens during the test.

Your child needs to lie still during the test. If this will be difficult for your child, they may be given sedative medicine. This will help your child stay calm during the test. Anesthesia may also be an option. This is medicine that causes your child to fall asleep and not feel pain or discomfort during the test.

A spinal tap is done by a trained doctor. Ask your child's doctor in advance if you can stay with your child in the hospital room. Your child may bring along a favorite toy, such as a stuffed animal, for comfort.

• Your child changes into a hospital gown and lies on a hospital bed.
• If needed, anesthesia is given to your child. A trained nurse (anesthetist) or doctor (anesthesiologist) helps with this process. Your child's breathing, heart rate, and blood pressure are then watched during the test.
• If your child is awake during the test, they are asked to curl into a tight ball and then remain still.
• The medical staff cleans your child's lower back so that the skin area is sterile.
• The medical staff uses medicine to numb the area.
• The doctor puts a hollow needle through the back into the small space that holds the fluid in the spinal canal. Sometimes the doctor inserts the needle more than once to find the best place to draw the fluid. Once the needle is in place, the fluid sample is slowly collected. Your child will need to remain still. The pressure of the fluid may also be measured.
• If the doctor needs to inject medicine into the spinal canal, it will be given through the same needle after the CSF is collected.
• The doctor then removes the needle. The area is cleaned and bandaged.

Follow all directions from your child's doctor. Schedule a follow-up appointment to review the results of the test.

Your child will need to lie still and rest after the test. Some soreness in the low back is normal. You can give your child pain medicine, such as acetaminophen.

Some children may have a headache after a spinal tap. The headache is usually mild and goes away on its own. Your child's doctor may prescribe pain medicine for a headache.

For more severe headaches that don't go away, the doctor may advise an epidural blood patch. This is a procedure in which the person's own blood is injected through the epidural at or near the spinal tap site. This seals the area and prevents spinal fluid leakage.

Contact your child's doctor if your child has:

• A fever of 100.4°F (38°C) or higher, or as directed by your child's doctor.
• A seizure caused by fever.
• A headache that is severe or lasts longer than 2 days.
• Muscle aches or lower back pain that is severe or lasts longer than 2 days.
• Tingling or weakness in the legs.
• Any change in behavior or level of activity.
• Confusion or trouble waking up.
• Bleeding from the needle site that doesn't stop.
• Clear fluid leaking from the needle site.
• Symptoms that don't get better, or get worse.

Before you agree to the test or procedure for your child make sure you know:

• The name of the test or procedure.
• The reason your child is having the test or procedure.
• What results to expect and what they mean.
• The risks and benefits of the test or procedure.
• When and where your child is to have the test or procedure.
• Who will do the procedure and what that person's qualifications are.
• What would happen if your child did not have the test or procedure.
• Any alternative tests or procedures to think about.
• When and how will you get the results.
• Who to call after the test or procedure if you have questions or your child has problems.
• How much will you have to pay for the test or procedure.