Do I Need a Lumbar Puncture? (Everything You Wanted to Know)
A lumbar puncture, also known as a spinal tap, is a diagnostic procedure that can test for a number of neurological conditions. From multiple sclerosis to meningitis, there are certain health concerns that can be more accurately diagnosed through the use of this technique. But when is it necessary? Is it always necessary to undergo this test to get an accurate diagnosis? Let’s take a look at the facts.
The procedure is called a lumbar puncture, or some people call it a spinal tap. I’m a neurologist and medical doctor, and I’ve been in practice doing this type of procedure since the early 1990s. I’ve probably done thousands of these procedures. I do call them spinal fluid examinations or lumbar punctures. The term “spinal tap” somehow has a connotation that brings a lot of fear and worries to people, so I just avoid using it altogether.
The Spinal Fluid
This is a routine test that measures certain aspects of spinal fluid. The test is used to measure the pressure of the spinal fluid, certain chemicals related to the spinal fluid, or whether or not there is an infection or other biomarkers in the spinal fluid. Essentially, the possibilities are pretty limitless, just like all the different blood tests that you can have done. Many of those tests can be done on spinal fluid, but sometimes the testing is more specific when spinal fluid is examined.
When I was taught to perform this test, I was told that at any given moment in time, there is about 140 mL of spinal fluid present within the spinal and skull cavities. This is a fluid produced at the center of the brain in the choroid plexus. There are two main areas in the brain where you can find big cavities filled with spinal fluid. This spinal fluid will flow through channels and aqueducts in the brain to ultimately bathe the spinal cord and brain. This way, the spinal cord, and brain almost float inside the skull.
The spinal fluid is a tissue in the body. It is biologically active, which means it does things like help with regenerative medicine and stem cell treatments. For example, the spinal fluid can communicate with stem cells that came from your bone marrow and have moved into the spinal fluid. This can help them do their jobs better.
A Spinal Fluid Examination
You have about 140ml of spinal fluid present and you’re constantly making more. The very small amount of fluid that’s removed during a test is going to be replaced. We tell our patients to arrive at the clinic well-hydrated for this procedure. It is always better to be hydrated if you are going to have blood or spinal fluid drawn. This makes the process much easier for your doctor or the person performing the procedure.
Try to arrive relaxed. I always tell my patients that getting a blood test is only slightly more complicated than having blood drawn, and by and large, it’s not any more uncomfortable. We do not resort to fluoroscopy, which is kind of like live x-ray guidance to do the lumbar puncture. It really isn’t necessary.
A lumbar puncture typically takes around 15 minutes and begins with the patient lying face down on their side with knees pulled as tight against their chest as possible in order to expose more surface area of their lower back. When they are laying on your side as they assume the correct position for the procedure, I can feel the little finest processes and the space between them. They are called the L4-L5 Innerspace.
The spinal cord has already ended. It is not possible to pierce the spinal cord with a lumbar puncture. There are nerves below the level of the spinal cord, called the cauda equina, but they move out of the way. In the worst case, they might feel a little tickle, but we will numb them up so it won’t happen.
The Injection Site
This is a sterile procedure. The skin will then be sterilized using an antiseptic solution. We use an iodine-based solution called Betadine to scrub your skin, to remove the surface bacteria, and minimize the likelihood of infection. I want to have a nice square open spot where I’m going to do the procedure and everything else is covered by a sterile drape.
Then, a numbing medication is injected at the injection site.
We use 1% lidocaine with a 30-gauge needle. I will then make a bleb, which means the needle only reaches the subcutaneous area of your skin to numb it up. And honestly, it’s probably the part that hurts the most. It’s pretty minimal, right?
Then, I’m going to take a little bit bigger syringe and fill it with lidocaine. With my hand on your back, what I’m going to do next is very slowly infiltrate the area that the spinal needle is going to go into with lidocaine. At this point, you’re going to feel some pressure. If I need more lidocaine, I take the needle out and get more lidocaine. Then I put the needle back in.
By the second time I put the needle in, you’re already numbed up. So you are not going to feel pain from here on.
Extracting the Spinal Fluid
We will wait for a couple of minutes for the numbing medicine to really kick in. I’ve put sterile gloves on at this point. On my sterile tray, I have laid my opened tubes where the spinal fluid is collected.
This is then followed by the insertion of a thin needle in the space between two vertebrae, L4 and L5 until it reaches deep enough into the CSF sacs. Generally, because I’m very experienced at this, I can kind of feel like I’m in the right place. Then, I take the center part out of this needle, and guess what? Spinal fluid begins to leak now.
What should we see next?
A healthy spinal fluid looks clear.
A yellow spinal fluid will mean acute spinal meningitis, and that’s a medical emergency. We don’t do lumbar punctures in the clinic for that kind of medical emergency.
If somebody has a lot of blood in their spinal fluid, one of two things has happened. If they had an arachnoid hemorrhage or if an aneurysm bursts, again, that’s a medical emergency and a very serious problem. People present with the worst headache of their life. You never ever see these in the neurology clinic.
Sometimes we will see a little bit of blood in the spinal fluid. This is not unusual and it usually goes away quickly. We know that it was just a small amount of blood and it is not dangerous. In fact, sometimes this can be helpful.
The normal pressure’s like 12-22 cmH2O. When our pressure gets high, say 26cmH2O and above, we need to lower it. I’ve seen it happen before. We can do that in a couple of ways. One is by taking off extra spinal fluid and another is we put them on medicine to help lower the pressure.
WBC and RBC
We also need to check for white blood cells (WBC- which are the immune system cells). If a person is suspected to be having Multiple Sclerosis (MS) and has numerous WBCs in their spinal fluid, they don’t have MS. They have something else going on. Red blood cells (RBC) should also be checked. But as a general rule of thumb, there can be up to 10,000 RBCs for every WBC.
Protein and Glucose
We should assess the protein and glucose levels. These are especially important when you have a bacterial infection, for example. Bacteria like to gobble up glucose or sugar, so low sugars are seen in bacterial infections. This is typically seen in meningitis and by large we don’t see that in the neurology clinic.
Protein can sometimes be high in some infections, some inflammatory disorders, and even in some neurodegenerative disorders like ALS. You cannot always use protein levels in spinal fluid to diagnose Lou Gehrig’s disease. However, if protein levels are high, that is a supportive finding.
Bacteria and Fungus
We also use one tube for microbiology. We will be looking for bacteria, including mycobacteria (present in Tuberculosis), and fungus. The pathologists who receive the spinal fluid will look at it under a microscope and do some culturing of the spinal fluid.
Usually, in the outpatient neurology clinic, we don’t see any of that.
Spinal Fluid Tests for Alzheimer’s Disease and Multiple Sclerosis
We need a fourth and fifth tube for Alzheimer’s disease and Multiple Sclerosis (MS). In MS, we’re testing for immunoglobulins that are in your spinal fluid. This will help us understand if you have a higher level of these immune globulins in your spinal fluid than in your blood.
Alzheimer’s disease is a condition where we can track biomarkers more effectively. There are certain changes in spinal fluid that are specific to a certain disease. A protein called Beta amyloid 42 is common in Alzheimer’s disease. This protein rises when the brain is under stress, like from lack of sleep. But when you get more sleep, the levels go back down.
In the case of Alzheimer’s disease, an insoluble protein called amyloid builds up. This protein forms when nerve cells break down. As those nerve cells break down, they release a protein called TAU. TAU is made from a part of the transport machinery of the nerve cell that takes stuff from the nerve cell body to the axon. TAU is another protein found in the spinal fluid or found in the brains of people with Alzheimer’s disease and we can measure it in the spinal fluid. This actually represents nerve cell injury.
We aim to identify the changes before they really become a problem. We want to know about Alzheimer’s disease as early as we can so we can stop it.
After taking all the samples we need, the patient is going to straighten their legs. We’re going to kind of massage the area a little bit and remove those sterile drapes. The nurse is going to come around and put a bandaid on your back.
We suggest that you drink lots of fluids, get plenty of rest, and relax on the sofa. You can watch your favorite show on Netflix or watch a movie. For most people, this procedure will not be a problem.
Will there be unwanted effects?
There is a very small percentage of people who develop a post-lumbar puncture headache. Admittedly, these are not fun. They are not dangerous and they are treatable. If you get a headache after a Lumbar Puncture, it is probably because the brain is settling down and there is some stretching of the meningeal layer around the brain. This happens when you are lying down, but when you stand up, the pressure on your head increases and causes headaches. Initially, this can be treated with caffeine.
No one has ever died or got paralyzed undergoing this diagnostic procedure. If you’ve heard this, I’m going to tell you that is the wrong information. If you are worried about MS, elevated spinal fluid pressure, Alzheimer’s disease, or any other condition, I want you to come to me. We will take care of you. You don’t need x-ray guidance for the procedure. It is very easy and less expensive than an x-ray. The procedure is also covered by insurance.
So, what do you think? Do you need a lumbar puncture? Are you curious about the spinal fluid examination process? We hope that this article was both informative and helpful. If you have any questions or concerns, please don’t hesitate to reach out to us. We would be happy to schedule a discovery call with you so that we can discuss your specific needs and see how we can help. Thank you for reading!
Feeling apprehensive about a lumbar puncture? In need of more information on the spinal fluid examination process? We’ve got you covered – let us give you an in-depth look into this important test. We’d be happy to schedule a discovery call with you. During this call, we can discuss your symptoms in more detail and come up with a plan tailored specifically for you.
If you haven’t joined our Private Facebook Group, please go HERE.
DISCLAIMER: The information in this email is not intended nor implied to be a substitute for professional medical advice, diagnosis, or treatment. All content is for general informational purposes only and does not replace a consultation with your own doctor/health professional