Updated September 30, 2014.
Written or reviewed by a board-certified physician. See About.com's Medical Review Board.
"I Have Headaches, Why Do I Need a Lumbar Puncture?"
Headaches are not always primary disorders, like a migraine or tension-type headache, but rather indicators that something else is going on in the body. For instance, some severe headaches are really signals of a dangerous process occurring in the nervous system. Examples include:
If your doctor is worried that your headache is really one of the above conditions, then he may perform a lumbar puncture or send you to the emergency room for one.
What is a Lumbar Puncture?
A lumbar puncture is a neurological procedure performed to access the spinal canal where cerebrospinal fluid (CSF) flows. Lumbar punctures are performed for diagnostic or therapeutic purposes. For instance, lumbar puncture is utilized in making the diagnosis of meningitis, which requires analysis of the cerebrospinal fluid. A lumbar puncture is also used to administer chemotherapy in a patient with cancer or anesthetics in a woman in labor.
How is a Lumbar Puncture Performed?
First, your doctor will carefully position you, as this is critical to accessing the CSF safely and efficiently. He will ask you to sit on the edge of your bed and "arch like a cat," or ask you to lie on your side in the fetal position, known as the lateral recumbent position. These two positions allow your doctor to best access the CSF.
Your doctor will then clean the skin on your back and inject a numbing agent. This is the part that usually stings the most.
After the numbing agent is injected, your doctor will insert the spinal needle between two vertebrae in your lower back. Once the spinal needle reaches the right spot, CSF will flow into collection tubes. But first, if you are lying in the lateral recumbent position (on your side), your doctor may take an opening pressure with a manometer. Detecting the opening pressure is especially useful in diagnosing medical conditions like idiopathic intracranial hypertension or bacterial meningitis, two conditions that cause a high intracranial pressure (>250mm H20).
Typically, the smallest volume needed of CSF is collected, around 3-4 mL. The CSF is then analyzed carefully to aid your doctor in making a diagnosis. For example, if your doctor suspects meningitis, he will order a gram stain and culture of the CSF, along with CSF protein and glucose.
What are the Potential Complications of a Lumbar Puncture?
The most common complication of a lumbar puncture is headache, which occurs in about 36% of patients. The cause of the headache is leakage of the CSF through the site in your back where the needle was inserted ("puncture site."). The potential for this complication is reduced by your doctor using a smaller spinal.Â
In the case of a spinal headache, your doctor may suggest lying down, intravenous fluids, caffeine, or even a blood patch. A blood patch entails a surgery in which your own blood is injected into the puncture site. This compresses the hole, preventing any further spinal fluid leak.
Brain-stem herniation is the most serious but very rare complication of a lumbar puncture. Sometimes, your doctor will have you undergo a CT scan of your brain prior to having a lumbar puncture to assist in identifying any pressure elevations in your brain, which would increase your change of herniation.
Bleeding at the puncture site may also occur and cause a spinal hematoma. Again, this is uncommon. Your doctor will use his discretion when doing a lumbar puncture if you are on a blood thinner.
Other potential rare complications include infection at the puncture site, lower back pain, and subarachnoid epidermal cyst.
Do Lumbar Punctures Hurt?
This is a good question and really varies by the individual. Often, the most uncomfortable part of the procedure is the numbing agent that is injected into the skin, prior to placement of the spinal needle. This feels like a bee sting. Then, when the doctor is placing the needle into your back, you will feel a pressure-like sensation, that is relieved once the needle is removed. Overall, the procedure is generally well-tolerated, and while it may be anxiety-provoking, is fairly quick and without much discomfort.
Take Home Message
Lumbar puncture serves as a window to our nervous system and can provide critical diagnostic information and therapeutic means. If you are going to have a lumbar puncture and have concerns, please speak with your doctor beforehand so that you feel prepared and at ease.
Sources
Ellenby MS, Tegtmeyer K, Lai S, Braner DAV. Lumbar Puncture. N Engl J Med 2006; 355:e12.
Seehusen DA, Reeves MM, Fomin DA. Cerebrospinal Fluid Analysis. Am Fam Physician. 2003 Sep 15;68(6):1103-1109.
Stella CL, Jodicke CD, How HY, Harkness UF, Sibai BM. Postpartum headache: is your work-up complete?Am J Obstet Gynecol 2007;196(4):318.e1-7.
DISCLAIMER: The information in this site is for educational purposes only. It should not be used as a substitute for personal care by a licensed physician. Please see your doctor for diagnosis and treatment of any concerning symptoms or medical condition.