What is a spinal tap (lumbar puncture)?
A spinal tap, also called lumbar puncture, is done to measure the amount of pressure in the spinal canal or to remove a small amount of cerebral spinal fluid (CSF) for testing. Cerebral spinal fluid is the fluid that bathes your child's brain and spinal cord. In some cases, a spinal tap may also be done so medication can be injected into the spinal fluid, or to remove excess CSF in babies with hydrocephalus (a condition in which there is an overproduction or lack of absorption of the cerebral spinal fluid that is found inside the ventricles, fluid-filled areas, inside of the brain). A special needle will be used for the spinal tap.
Getting ready for the test
Your child will lie on his or her side on a table and be asked to "curl up in a tight ball." Alternatively, he or she may be asked to lean over a table. A technician or nurse will stand beside your child to help him or her hold very still and explain what the doctor is doing. Remaining still is very important and will make the test go more smoothly. The doctor will feel your child's back for a space between the bones of the lower part of the spine to insert the needle. The doctor will clean your child's back with an antiseptic.
What is involved with the test?
The doctor may numb the spot for the spinal tap by injecting a special medication or by applying a topical medication. This shot stings for a few seconds, but it will make the spinal tap less painful for your child. Then, the doctor will put the special needle through the numbed skin, and into the space where the CSF is found. Your child will feel some pressure while the needle is being pushed in. He or she must stay very still. The CSF will begin to drip out of the needle and a small amount will be collected in test tubes.
If the doctor needs to inject medication in the spinal canal, it will be given through the same needle after the CSF is collected. When the test is completed, the needle will be removed and an adhesive bandage will be placed over the injection site. The test tubes will be taken to the lab.
Sometimes, intravenous (IV) conscious sedation may be used for the procedure. On rare occasions, the spinal tap is done while your child is under general anesthesia. If anesthesia is used, your child will not be allowed any food or drink from the night before the test until after the test is completed. Your child may remain sleepy for a short time after the test is complete. Usually, when anesthesia is used, the child is not aware of the test and will not remember it later.
What happens after the test?
Your child's doctor will discuss the lab report and treatment plan with you. Some of the studies can be completed in one day while others may take 2 or 3 days. Your child's doctor and nurses will be available to answer your questions.
Headache may occur in 10% to 30% of patients following lumbar puncture. Needle size and type and positioning can all be factors in post lumbar puncture headaches. The headache is usual mild and resolves on its own. Your child's doctor may prescribe pain medication for your child's headache.
For more severe headaches, your child's doctor may recommend an epidural blood patch. This is a procedure in which the person's own blood is injected epidurally at or near the lumbar puncture site to seal the area and prevent spinal fluid leakage. Intravenous caffeine is another option. Both have proven effective in providing pain relief after a lumbar puncture.