DIMENSIONS Summer 2005

LUMBAR PUNCTURES

by Bonnie Lash

Many studies here at the University of Washington’s Alzheimer’s Disease Research Center involve having one or more lumbar punctures over time. A lumbar puncture (or spinal tap) allows us to obtain a sample of cerebral-spinal fluid (the fluid that surrounds the brain and spinal cord) in order to identify and measure certain proteins and hormones that may be involved in neurological diseases such as Alzheimer’s disease.

Here are a few frequently asked questions and answers to help you decide if you are willing to participate in these types of studies.

Is a lumbar puncture (spinal tap) painful? One of the things that we are measuring in these studies is stress hormones. These stress hormones become elevated during painful experiences; therefore, we want to make this experience as painless and stress-free as possible. After positioning you on your side, with your knees up and your chin curled towards your chest, we will inject a local anesthetic in your back. This may sting for just a brief moment. The anesthetic should then make the rest of the procedure nearly painless and we will inject more if you feel any discomfort. Some people complain of leg cramping from lying in the curled position, but these cramps will go away as soon as the procedure is over and you straighten your legs. The procedure usually takes about 20 to 30 minutes.

How much fluid do you take? We take a little less than two tablespoons of fluid for our analysis.

Can a lumbar puncture (spinal tap) cause serious harm to me? This is a safe procedure and it is very unlikely that anything serious would happen to you. The spinal cord ends about 5 inches above the area where we are doing the spinal tap. There are some nerve roots that dangle from the spinal cord in the area where the needle is placed to obtain the fluid. In rare instances if the needle touches one of these nerve roots, it may send a “zinger” down into your hip and leg. This is a very short temporary discomfort that goes away immediately as the doctor moves the needle. There will be no damage to the nerve root.

Are there any common complications? You may have a mild headache or some mild discomfort in your back after the procedure. These symptoms are usually relieved with Tylenol. When we make our follow-up call the next day, most people state that they feel as if they had nothing done and that they are fine. In rare cases some people experience a post-lumbar-puncture headache. This has happened in only about 1 percent of the people who have been involved in our studies. You will know if you are experiencing this type of headache because it is very dependent on your position. You will feel fine when you are lying down, but will be unable to sit up or stand without feeling a painful headache. Sometimes this headache is associated with nausea and/or vomiting. If you experience a post-lumbar-puncture headache, we will have you return to the VA Medical Center. An anesthesiologist will take about two tablespoons of your own blood from your arm, find the spot on your back where we did the lumbar puncture, and inject the blood into that spot. It is thought that post-lumbar-puncture headache is due to continued leaking of spinal fluid. The blood works as a patch, similar to patching a tire. The headache disappears almost immediately after the blood patch is completed. Because of the very narrow special needle that we use to obtain spinal fluid, this complication is rare. We will provide you with instructions to minimize this complication and will contact you the next day to see how you are doing.

If you have further questions, feel free to contact Bonnie Lash, RN, MN, CPHQ at 206-277-5106.


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