Lumbar puncture

The lumbar puncture , also known as spinal tap, is a diagnostic test that is extracted cerebrospinal fluid . The CSF supplies the central nervous system , thus preventing the brain and spinal cord from having any friction with the bone when performing any type of movement; In addition, it is responsible for the exchange of substances to keep neurons in good condition.

The test is done by inserting a needle into the spine until it reaches what is called the spinal canal.

Why is it done?

Lumbar puncture is a diagnostic test in which cerebrospinal fluid is extracted, which supplies the central nervous system, made up of the brain and spinal cord. Your doctor may request the test if you suspect any of the following conditions.

Meningitis

A disease that arises from the inflammation of the meninges, the membranes that surround the brain by bacteria or a virus ; it occurs especially in children and young people. Lumbar puncture can diagnose this condition.

Subarachnoid hemorrhage

The subarachnoid space is known as the space in which the cerebrospinal fluid is housed. Thus, in the event of a certain blood vessel rupture , the fluid extracted by lumbar puncture has a reddish color.

Multiple sclerosis

Lumbar puncture makes it possible to establish the specific diagnosis of this disease. Multiple sclerosis is a chronic, degenerative condition of the central nervous system , leading to symptoms such as muscle weakness, vision disturbances, numbness in the extremities, and difficulty with both attention and concentration.

Hydrocephalus

Although the lumbar puncture itself is a diagnostic test, it is also used as a treatment for hydrocephalus. Hydrocephalus is a disease characterized by the accumulation of cerebrospinal fluid in the brain , exerting great pressure on it. Therefore, lumbar puncture can be used in a timely manner to remove CSF and relieve some pressure.

Does a lumbar puncture hurt?

If you must undergo this diagnostic test, surely one of the main questions you have in mind is whether or not it hurts.

Well, the truth is that lumbar puncture is a somewhat painful test ; Of course, everything depends on the patient and their degree of tolerance to pain, as well as the doctor himself. In expert hands and in patients with an adequate body weight and without any type of disease such as osteoarthritis or scoliosis, it is very painless; some point out that even less than an intramuscular injection.

In the case of obese patients , in whom it is not so easy to reach the spine, it may be a somewhat more painful test. The same occurs with patients with osteoarthritis of the spine.

How is a lumbar puncture performed?

This test lasts approximately 15-20 minutes ; the procedure itself takes no more than a minute, so the rest of the time is spent preparing the patient. The lumbar puncture is performed on an outpatient basis and it is advisable to be accompanied since after its performance it is usual to feel some pain in the area, as well as to be dizzy.

Regarding eating during the hours prior to the test, it is not necessary to go on an empty stomach. However, it is recommended to avoid caffeinated drinks and alcohol.

Process

To begin the test, the patient is placed in a venous line in his arm, through which the relaxing drug is introduced that will allow him to remain calm during the lumbar puncture; It is not always necessary, but it is advisable in patients who are averse to needles or who are not very tolerant of pain.

The patient should lie on a stretcher in the fetal position , with the knees bent toward the chest; in this way, the back is slightly curved, leaving space between the vertebrae for the passage of the needle.

Once the patient is ready for the puncture, the doctor proceeds to clean and disinfect the skin. He then injects an anesthetic and, once it has taken effect, inserts a long needle to extract the cerebrospinal fluid ; it is common to feel great pressure on the back. Still, it is important that the patient remains calm and still during the test.

When the physician has removed the CSF, proceed to carefully remove the needle. After the test is complete, the patient must lie down for approximately one hour.

After the test

After the lumbar puncture is completed, some patients have a headache ; it is one of the most common side effects. In addition, it is sometimes accompanied by nausea, vomiting, and dizziness; It is also common to feel great pain and tenderness in the lower back, which can affect the legs and therefore movement.

Lumbar puncture results

Once the test is finished, the patient must wait a few days to obtain the results of the test. To establish the diagnosis, a large selection of factors related to cerebrospinal fluid are taken into account.

On the one hand, the outlet pressure , whose values ​​must range between 70 and 180 mm H20. Values ​​above what is established implies a tumor or any type of abnormality that affects the brain and / or spinal cord. On the other hand, the appearance of the CSF must be transparent; if it is cloudy it corresponds to an infection and, if it is reddish, it implies the rupture of one or more blood vessels.

In addition, gamma globulin , a protein that is studied in suspected cases of multiple sclerosis; their normal values ​​range between 3 and 12 percent of total protein. And finally, the white and red blood cells; With respect to the former, under normal conditions there should be between zero and five per field, and, as for red blood cells, there should be none in the cerebrospinal fluid.

Lumbar puncture: risks and complications

The lumbar puncture, despite being a very safe test in expert hands, is still an invasive examination. Therefore, although they do not occur too frequently, there are complications; The vast majority of them occur during the lumbar puncture, although there are also others that can be given several hours after the test.

• One of the complications of lumbar puncture is the leakage of cerebrospinal fluid through the puncture site once the test is finished. In this case it is important to go to the emergency room.
• A local infection can also occur if the punctured area has not been properly cleaned and / or disinfected.
• During the test, the patient may have an allergic reaction to anesthesia .
• And finally, damage to the spinal cord can occur , although if the lumbar puncture is performed by a doctor with training and experience in the field, it is highly unlikely.

The lumbar puncture is one of the most common medical tests, both children and adults and seniors. And it is that it allows diagnosing a large selection of serious infections that affect the central nervous system, as well as other disorders of the brain and spinal cord. The CSF obtained is analyzed in the laboratory.