A lumbar puncture (LP), likewise dubbed a spinal tap, is an invasive outpatient procedure offered to rerelocate a sample of cerebrospinal fluid (CSF) from the subarachnoid room in the spine. (This test is equivalent to a blood test, in which a needle is placed into an artery to collect blood for testing.)

How does a lumbar puncture work?

Your brain and spinal cord are surrounded and bathed by a clear liquid called cerebrospinal liquid (CSF). This liquid is produced in the ventricles of the brain and circulates via the subarachnoid room of the brain and spinal cord (check out Anatomy of the Spine).

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During a lumbar puncture, a hollow needle is inserted with the skin in the lower earlier. The needle passes between the vertebrae and right into the spinal canal. A lumbar puncture deserve to be used to:

collect CSF for testing to detect condition conditions measure CSF pressure to detect hydrocephalus deliver anesthetic numbing agents to the spinal cord treat/relieve hydrocephalus regulate CSF press and also relax the brain during surgical treatment

What does a lumbar puncture show?

Many conditions deserve to be detected in the CSF including:

infection of the membranes surrounding the brain and also spinal cord (meningitis) viral infection (encephalitis) tumors (lymphoma, cancer) autoimmune disorders favor multiple sclerosis

In addition to experimentation for abnormal cells, the CSF push can be measured to determine if you have a condition dubbed hydrocephalus. The normal press of CSF is between 70 and also 180 mm.

Who performs the test?

This test is perdeveloped by a physician in the office or in the hospital.

How should I prepare for the test?

On the day of the exam you have the right to eat a consistent breakfast. Before the test, you will certainly be asked to readjust into a hospital gvery own and an intravenous (IV) line will be inserted in your arm. The medical professional or nurse will certainly comment on the test with you, describe the threats, answer any inquiries, and have you sign consent out forms. You might receive a mild sedative, intravenous fluids, or extra medication before the procedure.

What happens throughout the test?

Although the liquid collection just takes a few minutes, the entire test takes about 20 minutes.

Tip 1: prepare the patient You might be provided a sedative to make you drowsy and also peaceful. A physician and also at least one assistant will be in the room. You will certainly lie on your side via your knees attracted to your chest so that your spine is curved; in some cases you may sit on the table and lean forward onto some pillows instead. After cleaning your earlier via a cooling antiseptic, the physician will numb the location of your lower ago where the needle will be placed. This might reason some brief stinging.

Step 2: insert the needle Next, a hollow needle is placed between the 3rd and also fourth lumbar vertebrae right into your spinal canal (Fig. 1). The needle does not touch the nerves of your spinal cord. Your medical professional will certainly collect in between 5 to 20 ml of cerebrospinal liquid in 2 to 4 tubes.


Figure 1. A needle is placed in the subarachnoid room at the level of the 3rd and fourth lumbar vertebra to collect a sample of cerebrospinal fluid.

You will probably feel pressure when the needle is inserted, and also some civilization feel a sharp stinging sensation as soon as the needle goes via the protective dural layer that surrounds the spinal cord. Although you may feel some discomfort, it is crucial that you lie still. Let your doctor know if you are feeling pain.

Step 3: measure CSF pressure (optional) You will certainly be asked to straighten your legs to decrease abdominal push and also increase cerebrospinal liquid push. The needle is attached to a meter and also the push in your spinal canal is measured.

Tip 4: insert a lumbar drainpipe (optional) In situations of hydrocephalus, a catheter may be placed to consistently remove CSF and also relieve push on the brain.

What happens after the test?

The medical professional will certainly use press to the puncture site, then apply a bandage. You will need to remainder in bed for at least an hour, and also prevent strenuous task for at leastern 24 hours. You must also drink plenty of fluids. Let your medical professional understand if any kind of blood or fluid is leaking from the puncture website.

What are the risks?

A lumbar puncture is safe for many people. Some world obtain a serious headache recognized as a "spinal headache" led to by CSF leakage.

Rare complications include back or leg pain, accidental puncture of the spinal cord, bleeding in the spinal canal, and brain herniation resulted in by a sudden decrease of CSF push.

How execute I get the test results?

The physician will certainly acquire prompt information from the color of the CSF, which is generally clear. A reddish shade indicates a bleed or subarachnoid hemorrhage. A cloudy or yellowish color shows an infection, possibly meningitis. Thostormy evaluation by a laboratory will detect substances such as antibodies, blood, sugar, bacteria, cancer cells, and excess protein or white blood cells. The laboratory test results have the right to take much longer and will certainly be debated with you when completed.


If you have further questions about this diagnostic test, contact the medical professional that ordered the test.


arachnoid mater: one of 3 membranes that surround the brain and also spinal cord; the middle web-prefer membrane.

cerebrospinal liquid (CSF): a clear liquid produced by the choroid plexus in the ventricles of the brain that bathes the brain and also spinal cord giving them assistance and also buoyancy to defend from injury.

hemorrhage: external or internal loss of blood from damaged blood vessels. Hemorrhage is stopped by blood clotting.

hydrocephalus: an abnormal buildup of cerebrospinal liquid generally resulted in by a blockage of the ventricular system of the brain. Increased intracranial press can compush and damages brain tissue. Also referred to as “water on the brain.”

meninges: the 3 membranes (pia mater, arachnoid mater, and also dura mater) that surround the brain and also spinal cord.

meningitis: infection and inflammation of the meninges surrounding the brain and also spinal cord caused by bacteria or virus.

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subarachnoid space: the room between the pia and arachnoid mater of the brain and also spinal cord that has cerebrospinal fluid (CSF).

spinal canal: the hollow space within the bony vertebrae of the spine through which the spinal cord passes.

updated: 4.2018 reperceived by: Thomas Berger, MD, Mayarea Clinic, Cincinnati, Ohio

Mayarea Certified Health Info products are written and also developed by the Mayarea Clinic. We comply through the HONcode typical for reliable health indevelopment. This indevelopment is not intended to relocation the medical advice of your health treatment provider.