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Lumbar Puncture (Spinal Tap) for Cerebrospinal Fluid Analysis

This procedure is used to sample the cerebrospinal fluid, also called CSF. This fluid bathes the spinal cord, the nerve roots and the brain. The CSF sample is taken with a needle placed between the vertebrae of the lower spine.

Why It Is Sampled
A sample of this fluid may be needed for a variety of reasons. A physician may examine this fluid for signs of bleeding or infection around the brain. This fluid may help determine the cause of a patient’s unexplained headaches or seizures. It can also be examined for proteins associated with diseases such as multiple sclerosis.

In preparation for the procedure, the patient is positioned and the physician numbs the skin of the lower back. The fluid will be sampled from below the level at which the spinal cord ends, so the needle will not come in contact with the spinal cord.

Inserting The Needle
The physician places a needle into the numbed tissue and pushes it between the vertebrae of the lower back. The needle is carefully guided through the dura (the sheath surrounding the nerve roots) and into the subarachnoid space. The CSF will slowly drip out through this needle, where it will be collected in vials for examination.

End Of Procedure
When the procedure is complete, the needle is removed and a small bandage is placed over the entry site. The patient may be asked to remain lying down for a short time after the procedure to reduce the risk of a headache.

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