Lumbar puncture | Diseases and conditions: Medical tests.

What is lumbar puncture?

Lumbar puncture (also called spinal cord or spinal puncture) is a diagnostic test that allows the extraction for its study of cerebrospinal fluid (CSF). This fluid bathes the central nervous system (brain and spinal cord), avoiding colliding against the bone to make sudden movements and making exchanges of substances to allow good metabolism of neurons.
The test requires puncturing the spine from the back, with a needle so that the needle passes between the vertebrae and penetrate into the spinal canal. This channel consists of the meninges that surround the spinal cord.
Extracted CSF is subsequently studied in the laboratory analyzing its different components (glucose, cell, ions, etc). Alteration of each component can guide us towards specific pathologies of the nervous system, from infections such as meningitis to damage in the brain or bone marrow.
As it stands to reason, it is necessary to perform the test very carefully, as it can cause damage to the spinal cord with relative ease. However, the frequency of nerve damage after the test is very small. The main annoyance to persons who undergo a lumbar puncture is pain. The needle through the skin, muscles and ligaments of the spine, so it is usual that the procedure is painful. To avoid this can anesthetize the area doing this more bearable discomfort for the patient.

When a lumbar puncture is made

If you have been quoted for to perform you this test maybe you wonder why, as well, a lumbar puncture is performed when appear following alterations in a person:
Meningitis: is an inflammation of the meninges, the membranes that surround the central nervous system. The cause of this inflammation is infectious in many cases (for bacteria or viruses).
Encephalitis: inflammation in this case focuses on the brain. May be associated with meningitis, in that case is called meningoencephalitis.
Hemorrhage subarachnoid: space where is the cerebrospinal fluid (CSF) is known as subarachnoid space. When a blood vessel breaks blood to this area can be overturned and a lumbar puncture in CSF dyed red would be.
Reye's syndrome: the cause of this disease is unknown, is only known to occur in young children with one viral infection (influenza, for example) that treats them with aspirin. Alterations of the CSF may be key to a quick diagnosis.
Myelitis: as in encephalitis, spinal cord can also ignite.
Suspicion of neurosyphilis: when a person infected by syphilis does not properly respond to treatment or neurological symptoms should be a lumbar puncture to rule out presence of the bacteria at that level.
Multiple sclerosis: Although the main suspect of this disease appears when there are specific neurological symptoms, cerebrospinal fluid can help definitely opt for the diagnosis.
Treatment of Hydrocephalus: Hydrocephalus refers to the accumulation of CSF that puts pressure on the brain. Although it can not be used as a chronic treatment, in a timely manner can be a lumbar puncture to relieve the internal pressure of cerebrospinal fluid in certain diseases. Improvement can be found even in certain pathologies with normal CSF pressures to drain it (for example, the normal pressure hydrocephalus).

Preparation for lumbar puncture

If they are going to perform a lumbar puncture these are the issues that you must take into account to prepare yourself before the test:
Duration: the test will last a total of 15 to 20 minutes. The taking of the cerebrospinal fluid (CSF) will actually be a minute, the rest consists of the preparation of the material and area to puncture.
Income: lumbar puncture can be a query or a room of cures, in such a way that it does not require hospital admission. If there is reason to enter it would be for the State of the patient by her illness, not by the test itself.
Is necessary to be accompanied?: Yes, is recommended. There are people that are sore or rather queasy after the test. Also, you may be lying one hour after its completion and you can not do physical activity throughout the day. He is not recommended driving, perform household chores, etc.
Drugs: don't need to take any prior medication. You should tell your doctor all the medicines taken regularly and will decide if we will suspend some, especially blood thinners or anti-inflammatory drugs. It is important to also inform of allergies to medications or other products, if you have them.
Food: no need to remain in fasting before puncturing or after. Take a light meal and avoid taking all day coffee, alcohol and other exciting substances, including also the day prior to the test. If for any reason it should go on fasting to test the doctor warn you of this.
Clothes: you can introduce yourself to the procedure with the same clothes every day. When you get to the hospital or doctor's office may give you a gown to change you.
Documents: is essential to bring with you the steering wheel which shows the realization of lumbar puncture. The health insurance card is recommended. Normally you will not you any document after the test because it takes time to analyze the results.
Pregnancy and breast-feeding: lumbar puncture is not contraindicated in pregnancy or lactation, but that State should know because some biological constants that are studied and the anatomy of the spine will be altered during these stages.
Contraindications: lumbar puncture cannot be performed in people who have severe alterations of blood clotting or have very low levels of platelets. You can either be the test in people with low level of consciousness, clear neurological, suspected brain compression, etc. In many cases they have to the patient prior CT scan to make sure that there will be no complications of the central nervous system.

Lumbar puncture is done

First, the doctor will evaluate if it is necessary or not to perform a lumbar puncture, and if it must be urgently or it can be programmed for another day. The test urgently does not mean that you have more risk of complications, in any case the planning will be the same and be guaranteed the best conditions for the patient.
Your doctor will inform you of why can be positive to perform it, is, what information we can provide and what are the possible risks. It will give you an informed consent document outlining the main features of the procedure and you will have to sign it if you agree with its realization.
Sometimes, before the puncture, decides to do a CT scan to check that there are no changes in the nervous system that predispose to complications. It is not always necessary to perform this test. When to perform lumbar puncture ask you firstly that you change your clothes and views a comfortable gown for you and for the doctor who makes it for you. Then will measure you vital signs such as blood pressure, heart rate, respiratory rate and temperature, to check that you are in optimal conditions to put you to the test.
Sometimes placed you a via vein in the arm if it had introduced some medically during the process, although it is not common. Sometimes they will give you some relaxing drug so you stay sedated during the test, something that is recommended if you are nervous or are particularly sensitive to pain.
Prepared once you will be asked to you tumbes on a side table, with knees bent and embrace them. In this way, the back will be slightly curved and the vertebrae are separated, leaving holes for the passage of the needle. in a position that facilitates the realization of the test.
To proceed with the biopsy, the first thing that will will be clean skin with antiseptic to eliminate germs on its surface. Then they injected an Anaesthetic from the surface to deeper levels. You will feel a slight prick of the needle, and then a burning sensation at the very moment in which the anesthesia gets. When it did effect the local anesthesia will be a longer needle to reach the meninges and through them very carefully, just to take a sample of CSF but not reach the spinal cord. Throughout the process, you will notice a strong back pressure, but it is very important that you keep quiet all the time.
Once taken the sample be removed the needle. It is normal that the puncture point blood slightly, apply continued pressure for a few minutes to stop the bleeding. Then they will place a compressive dressing and you have to stay lying down for an hour. You can turn on yourself, but always lying.
The results may take from an hour to several days, depending on the urgency of the diagnosis. The dressing will keep it for at least two days, is normal in the days after the test to have pain in the area and need to take some pain reliever you your doctor will prescribe.

Complications of lumbar puncture

All invasive procedures involve complications, but the most serious are rare. They can appear during or after the puncture, whenever they arise should go to the emergency room. Some of them are:
  • Headache secondary to loss of cerebrospinal fluid (CSF) that if he is not relieved with conventional analgesia should go to emergency.
  • Exit of CSF by the point of puncture.
  • Bleeding from the puncture point (it can also appear a local hematoma).
  • Local infection with fever and inflammation that require antibiotic treatment.
  • Uncontrollable pain at the site of the puncture despite analgesia.
  • Reaction to anesthesia during the test.
  • Damage to the spinal cord (very unlikely).

Results of lumbar puncture

The results of lumbar puncture biopsy may take to be obtained and delivered from an hour to a few days. The following analysis will be carried out on the sample collected:
Outlet pressure: normal values are 70 to 180 mm H20. An elevation of the pressure may be due to occupation of space increased blood, cerebrospinal fluid (CSF) or tumor.
Aspect: it must be transparent, like water. If it is cloudy it may indicate infection.
Protein: normal values are from 15 to 60 mg per 100 mL. In the course of an infection total proteins increase.
Gamma globulin: is a special type of protein that is useful for the study of diseases such as multiple sclerosis. Their normal values are from 3% to 12% of total proteins.
Glucose: values tend to be around 80 mg per 100 mL. It is necessary to compare it with the levels of glucose in blood. In situations of infection will be decreased, since the germs feed on it.
Cells: typically found few white blood cells (from 0 to 5 per field) and no red cell. If there is white blood cells should rule out inflammation, and if there are red blood cells be ruled out due to own the puncture wound or a subarachnoid haemorrhage.
All of these tests will be performed by the physician. Along with the symptoms and the analytical studies can be a successful diagnosis to be able to advertise the necessary treatment.
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