Rarely, headaches can be the result of a serious medical condition requiring analysis of the cerebral spinal fluid (CSF) to help confirm or rule-out a diagnosis. Chronic meningitis, vasculitis, multiple sclerosis, and other auto-immune diseases are all detectable from abnormalities in the CSF. In addition, some patients suffer from alterations of the CSF pressure (either high or low), which can cause headaches. The procedure to collect a sample from the spinal fluid and/or measure its pressure is called a Lumbar Puncture, more commonly known as a spinal tap.
- What is a lumbar puncture?
- Why do I need one?
- How do I prepare?
- What happens on the day of my procedure?
- What happens after my procedure?
- Will I need additional help?
What is a lumbar puncture?
A lumbar puncture is a procedure used to collect cerebral spinal fluid (CSF) for analysis and to measure the pressure in the brain. Cerebral spinal fluid is a clear fluid that circulates in the space surrounding the spine and brain. It acts like a cushion protecting the brain and spine from injury. During the procedure, a hollow needle, or cannula, is used to penetrate the spinal canal at the level of the third-to-fourth or fourth-to-fifth lumbar vertebra in the low back. CSF then drips out through the needle and is collected. Its pressure is easily measured with a simple device.
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Why do I need one?
A lumbar puncture is most commonly performed to measure the pressure within the CSF and to collect a sample for further testing. The CSF can be evaluated for color, blood cells, bacteria, malignant cells, glucose, protein and many other chemical changes.
The results of the evaluation can be used to diagnose a number of different neurological disorders. Lumbar punctures can also be used to decrease spinal fluid pressure in patients with normal pressure hydrocephalus and intracranial hypertension. Lumbar punctures can also be used as an access method for spinal anesthesia, introduction of radio-opaque contrast dye (as is used in myelograms), corticosteroids, antibiotics, and chemotherapeutic agents.
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How do I prepare?
Preparing for your lumbar puncture is easy. Your provider will probably order several blood tests to be sure that you don't have any unusual bleeding or clotting. Some patients will be asked to have a brain scan (CT or MRI) performed prior to the procedure if you have never had one before. If you take a blood thinner, make sure you ask your provider when you should stop this medication. If you take Ibuprofen or aspirin frequently, you should stop taking them a few days before your spinal tap.
You should plan to spend at least two hours at the hospital on the day of your procedure. Although the actual spinal tap takes only a few minutes, numbing and cleaning the area and preparation can take about 30 minutes. You will want to wear loose fitting clothing to increase your comfort following your procedure.
You will also need to lie flat following the spinal tap for a minimum of thirty minutes to promote clotting at the site of the puncture.
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What happens on the day of my procedure?
We ask that you arrive as scheduled at the Neurology reception desk located in the outpatient clinic area. The procedure is performed in a regular patient examination room, typically on a Friday. Family members are usually not permitted in the room during the procedure, but may join you immediately after the procedure.
Before the procedure, you will be asked to empty your bladder. You will remove your outer clothing only and will be dress in a hospital gown so that it opens in the back. A healthcare worker will help position you on the exam table with your back curled and facing the provider to allow the spaces of the back bones to stretch open for easier entry of the small spinal needle. You will be draped with a sterile cloth and prepped with an antiseptic cleansing solution like iodine over the low back. This solution will feel cold. The provider will use a very small needle to numb a small area of the low back between the bones of your spine. You may feel some stinging for a brief time during this process.
Once the area is numb, the provider will insert a needle into your lower back, slowly advancing it toward the spinal fluid. Since the spinal cord ends approximately at the navel, and because the procedure is typically done lower down in the spine, risk of injury to the actual spinal cord is very minimal. Most people report feeling only pressure during this part of the procedure, not pain. More anesthetic can be added and you can be repositioned if necessary. Once the needle penetrates the cellophane-like lining surrounding the spinal fluid, the fluid will begin to drip out slowly. At this point, a small tube may be attached to the needle to measure the pressure of the fluid. The dripping CSF is collected in sterile tubes and sent to the hospital laboratory for analysis. Generally, less than a tablespoon of fluid is collected in total, divided up between four or more small vials. The entire procedure usually takes less than 30 minutes.
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What happens after my procedure?
Once the needle is removed, a small bandage is placed over the hole in your skin and you will be asked to remain flat on the exam table for a minimum of 30 minutes to help prevent any leakage of spinal fluid after the procedure. You will be encouraged to drink extra fluid while you recover and for the next two to three days. Although this will certainly result in additional trips to the bathroom, it may reduce the likelihood of headaches.
A headache following spinal tap occurs in up to 20 percent of patients. It typically occurs upon standing and is relieved by lying down. You should lie flat on your back or stomach (but not your side) for as long as you can the first 24 hours after the procedure or if you have a headache. Also, to minimize complications, it is recommended that patients avoid bending and heavy lifting for two to three days following the procedure. Even lifting a small child following this procedure can cause the clot formation to become dislodged, resulting in a headache. Your provider will tell you when it is safe to return to work. Most people can generally return to work in one to two days.
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Will I need additional help?
Some post-lumbar puncture headaches do not resolve with fluids and bed rest. If this happens, a procedure called an epidural blood patch [link] can be performed to relieve your symptoms. Rarely, the lumbar puncture/spinal tap can cause infection. You should monitor yourself closely for three to five days for signs of infection, including:
- Fever - temperature over 101°
- Drainage or redness at the site
- Severe stiff neck
- Persistent head pain that is not affected by acetaminophen (Tylenol)
- Nausea or vomiting
If you notice any of these symptoms, we advise you to contact your referring neurologist. If it is after hours, you may call the Johns Hopkins Bayview Neurologist on Call at (410) 550-0100.
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