Medical Tests

Lumbar Puncture: What is it and what is it used for?

Lumbar puncture is a diagnostic test in which a sample of the cerebrospinal fluid, a colorless substance that surrounds the brain and spinal cord. This liquid is mainly composed of water, calcium, sodium, potassium, chlorine, inorganic salts and other organic components. Its function is to cushion and protect the brain and spine from trauma. When this liquid changes its color, it is because there is some alteration in the organism and it will be necessary to perform this test to determine it.

lumbar puncture

What is a lumbar puncture

It is a medical test that will diagnose or rule out diseases by studying a sample of cerebrospinal fluid, which will analyze the amount of white blood cells, levels of glucose concentration and protein, and if there are bacteria present.

What is the lumbar puncture done for?

Lumbar puncture is performed to diagnose meningitis, but there are also other alterations for which this test may be indicated:

  • Alterations in the production and circulation of cerebrospinal fluid.
  • Inject chemotherapy treatment.
  • Infectious diseases such as meningitis, encephalitis or syphilis.
  • Bleeding around the brain.
  • Cancers related to the brain or spinal cord.
  • Diseases of the central nervous system such as Guillain-Barre syndrome or multiple sclerosis.

How lumbar puncture performed?

Before performing the test, you must sign an authorization so that the medical team can perform the puncture. On the other hand it will be necessary for someone to accompany you; your doctor will tell you any other details regarding the medicines that you must do without and you will have to inform him if you take any anticoagulant.

The duration of the lumbar puncture is approximately 30 minutes, the patient is placed in a fetal position, with the knee towards the abdomen and the chin against the chest, in this way the spaces between the vertebrae will be wider. The doctor will clean the area and place anesthesia, which will then measure the pressure of the fluid and collect the sample will introduce a fine needle between the bones of the spine. Finally the needle is removed, the area is cleaned and a bandage is placed. It is possible that the doctor recommends you to lie down for a few minutes after the lumbar puncture.

In some cases X-rays may be used or may be part of other procedures such as a CT scan or radiography, in which a contrast liquid has previously been introduced.

Abnormal results of lumbar puncture

There are several data that may indicate that there is a problem in the body from the lumbar puncture:

  • In case the cerebrospinal fluid looks turbid, it is related to infections.
  • If there is pressure in the fluid, it may be due to a pressure in the skull, if on the contrary, there is no pressure, it may be a tumor or a diabetic coma.
  • If there is an increase in protein in this substance, it is due to infectious or inflammatory conditions.
  • If there are high levels of glucose, it is a sign that blood sugar levels are increasing; if it is less, it may represent hypoglycemia, tuberculosis, meningitis, or any other bacterial or fungal disease.
  • In case the test has presented blood cells as white blood cells, it can be a sign of chronic disease, tumors, meningitis or an acute infection.

Risks of lumbar puncture

There are some risks when performing a lumbar puncture:

  • Risk of bleeding around the brain.
  • Discomfort while the exam is being performed.
  • Headaches, after the lumbar puncture.
  • Allergic reactions to anesthesia.
  • There may be damage to the marrow nerves if the patient moves during the examination.


Your doctor must perform tests prior to the puncture, to rule out the following conditions, in which it would be contraindicated:

  • If you have a tumor that puts pressure on the brainstem.
  • If your platelets are low.
  • If you take anticoagulants or aspirin.
  • If you have coagulation problems.