General Practice 2022

Punç&lumbar atilde; what é, what is it for, like é done and risks

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Punç&lumbar atilde; what é, what is it for, like é done and risks
Punç&lumbar atilde; what é, what is it for, like é done and risks

Lumbar puncture is a procedure that generally aims to collect a sample of the cerebrospinal fluid that bathes the brain and spinal cord, through the insertion of a needle between two vertebrae of the lumbar region until reaching the subarachnoid space, which is a space between layers that line the spinal cord, through which fluid passes.

This technique is used to identify neurological disorders, which can be infections, such as meningitis or encephalitis, as well as diseases such as multiple sclerosis or subarachnoid hemorrhage, for example. In addition, it can also be used to insert drugs into the cerebrospinal fluid, such as chemotherapy or antibiotics.

What is it for

Lumbar puncture has several indications, which include:

  • Laboratory analysis of cerebrospinal fluid to identify and evaluate diseases;
  • Measurement of cerebrospinal fluid pressure;
  • Spinal decompression;
  • Injection of drugs such as antibiotics and chemotherapy;
  • Staging or treatment of leukemias and lymphomas;
  • Injection of contrast or radioactive substances to perform radiographs.

Laboratory analysis is intended to detect the existence of alterations in the central nervous system, such as bacterial, viral or fungal infections such as meningitis, encephalitis or syphilis, for example, to identify bleeding, cancer or the diagnosis of certain inflammatory or degenerative conditions of the nervous system, such as multiple sclerosis, Alzheimer's disease, or Guillain-Barré syndrome.

How the puncture is made

No special preparation is required before the procedure, unless there is a clotting problem or the use of a medication that interferes with the technique, such as anticoagulants.

The person can be in one of two positions, either lying on their side with their knees and head close to their chest, called the fetal position, or sitting with their head and spine bent forward and with arms crossed.

Next, the doctor applies an antiseptic solution to the lumbar region and looks for the space between the L3 and L4 or L4 and L5 vertebrae, and an anesthetic drug can be injected there. Then, a thin needle is slowly inserted between the vertebrae, until it reaches the subarachnoid space, from where the liquid will drain and drip through the needle, being collected in a sterilized test tube.

Finally, the needle is removed and a bandage is applied to the bite site.This procedure usually takes a few minutes, however the doctor may not be able to obtain a sample of cerebrospinal fluid as soon as the needle is inserted, and it may be necessary to deviate the direction of the needle or re-prick another region.

Possible side effects

This procedure is generally safe, with low chances of presenting complications or risks to the person. The most common adverse effect that can occur after a lumbar puncture is temporary headache due to the decrease in cerebrospinal fluid in the adjacent tissues, and nausea and vomiting can also occur, which can be avoided if the person lies down for some time after the examination.

Pain and discomfort can also occur in the lower back that can be alleviated with pain relievers prescribed by the doctor, and although it is rare, infection or bleeding can also occur.

Lumbar puncture contraindications

Lumbar puncture is contraindicated in the presence of intracranial hypertension, such as that caused by a brain mass, due to the risk of brain displacement and herniation. It should also not be performed on people who have a skin infection that will be punctured or who have a brain abscess.

Furthermore, you should always inform your doctor about the medication you are taking, especially if the person takes anticoagulants such as warfarin or clopidogrel, due to the risk of bleeding.


Cerebrospinal fluid samples are sent to the laboratory for analysis of various parameters such as appearance, which is usually transparent and colorless. If it has a yellowish or pink color or a cloudy appearance, it may indicate infection, as well as the presence of microorganisms such as bacteria, viruses or fungi.

In addition, total proteins and the amount of white blood cells are also evaluated, which, if elevated, may indicate infection or some inflammatory condition, glucose, which, if low, may be a sign of infection or other diseases, as well as the presence of abnormal cells may indicate certain types of cancer.

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