What’s in a Name: Spinal Fluid Sampling

Medical terms can often make a simple process sound intimidating. “Venipuncture” sounds painful. The word “puncture” associated with anything on our body seems frightening. “Giving a blood sample” sounds routine. Yet, venipuncture is the proper medical terminology for the process of drawing a sample of blood.

And so it is with another test that’s particularly important to research in an Alzheimer’s Disease Center or Memory Disorders Clinic – sampling cerebrospinal fluid. Technically, this process is known as “lumbar puncture.” In lay terms,
it’s sometimes called “spinal tap.”

When Shakespeare wrote, “tis but thy name that is my enemy,” he didn’t mean ‘lumbar puncture,’ or ‘spinal tap,’ but the problem is the same. These off-putting terms, and erroneous beliefs associated with them, have given a safe, simple, virtually painless and very necessary procedure a bad name. So read on for the facts – not the frightening fiction – of a spinal fluid draw.

The Facts on Cerebrospinal Fluid Sampling

What is Cerebrospinal Fluid? Cerebrospinal (sir-'ree-bro-spy-nul) fluid and known as CSF, is a watery, serum-like fluid that circulates through the ventricles of the brain, and in the cavity of the spinal cord. It acts somewhat like a shock absorber for protection of these areas.

Is this test only for research? Lumbar puncture to collect CSF has many clinical uses. Common clinical uses include, identifying infection, cancer, inflammation, or bleeding. CSF can help physicians, select the best treatment and determining if the treatments are effective.

We do not yet have a marker for Alzheimer disease but the collection of the CSF in research settings may lead us to better markers.

Why is it important in brain research? Examining cerebrospinal fluid is a key part of research into healthy brain aging and brain disorders, like Alzheimer’s disease, and other dementing illnesses. CSF contains tau, other proteins, and important chemical particles, known as biomarkers.

Clinical trials in those with Alzheimer’s disease and other memory problems such as Mild Cognitive Impairment often include CSF collection to determine if a drug is changing the amount of these biomarkers. In other studies we collect CSF from healthy elderly volunteers to determine if the biomarkers can distinguish between those with and without the disease and if they can detect very early changes that might predict the onset of a memory problem.

Because cerebrospinal fluid directly “bathes” the brain, it is considered the best source in which to study those biomarkers related to brain health and disease. Some types of biomarkers related to brain health and disease may also be present in blood and urine, yet because these fluids undergo processing in the liver and kidneys, the type and concentration of biomarkers are not the same. Cerebrospinal fluid is the “gold standard” of source material for identifying and measuring biomarkers of normal brain aging and brain disease.

How is CSF obtained? CSF is obtained through a simple and safe process known as a lumbar puncture (lp). The sample is quick and involves no, or only the slightest discomfort. There is no risk of paralysis. The very small needle used is never in contact with the spinal cord.

The person giving a CSF sample can lie comfortably on his or her side on an exam table, or sit during the procedure. Just as in a venipuncture (blood draw), the skin is swabbed with a cleansing solution. A local anesthetic is injected under the skin where the needle will be placed. The area is made totally numb. A small needle is inserted into the lower back, below where the spinal cord itself ends in the spinal cavity. The needle slips easily between – not into – the bones of the spine to reach the fluid. Only about 3 tablespoons of fluid are drawn out.

Are there risks involved? There may be slight discomfort or bruising of the skin where the needle was inserted, similar to what may occur when giving blood. In less than 10% of cases, individuals report a headache which usually responds to treatment with over-the-counter pain reliever. In very rare instances, more severe headaches may occur. All precautions are taken to anticipate potential problems and minimize any risks. After resting for about 30 minutes, the person giving the CSF sample may resume routine activity.

Adapted from an article by Carol Edwards, Associate Director Education Information Core, University of Pennsylvania Alzheimer’s Disease Center From the University of Pennsylvania ADC “Quarterly” Newsletter, Spring 2006

The medical term for obtaining a blood sample is “venipuncture,” where a tiny and safe puncture is made in the vein with a needle to obtain blood. Similarly, the term for spinal fluid sampling is “lumbar puncture.” A needle makes a tiny and safe puncture of the lumbar space in the spinal canal to obtain spinal fluid. Note the base of the spinal cord, shown with a black arrow on the image above, in the lumbar canal. The needle, shown in grey, is never in contact with the spinal cord. There is no risk of paralysis.

Previous | Next