A lumbar puncture is a medical procedure to analyze the cerebrospinal fluid during which a sample of the fluid surrounding the spinal cord is taken by inserting a needle into the vertebral canal in the lumbar region and examined in a laboratory.
What is a lumbar puncture?
A lumbar puncture, in which a needle is inserted into the lower back to obtain a sample of cerebrospinal fluid and indirectly measure intracranial pressure (ICP).
Cerebrospinal fluid (CSF) is a clear fluid that surrounds the brain and spinal cord, and has several functions.
The sample taken from this fluid is sent to the laboratory for examination and analysis, and to check for:
- The presence of bacteria, fungi, or abnormal cells.
- glucose (sugar) levels in it.
- Protein types and levels.
- The type and number of white blood cells.
The doctor orders a lumbar puncture of the CSF for a diagnostic and therapeutic medical purpose as well in some pathological conditions including:
- If there is a cerebral hemorrhage (intracranial hemorrhage).
- Leukemia or other types of cancer.
- Diagnosis of various diseases of the nervous system such as meningitis, encephalitis and spinal cord inflammation.
- To check for multiple sclerosis or another autoimmune disease (Guillain-Barré syndrome).
- To diagnose and treat high cerebrospinal fluid pressure.
- It may also be used to perform lumbar anaesthesia (for example, before childbirth) to numb the lower body.
- Injectable cancer treatments.
- Dye (painting material) is injected for radiography.
Lumbar Puncture Steps
To do a lumbar puncture we must ensure that the place is completely sterile and follow the following steps:
Before the lumbar puncture:
- A blood clotting time may be tested before the lumbar puncture to ensure it is normal.
- Stopping the blood thinners in the person whose spinal fluid is to be punctured, such as aspirin or warfarin.
- Tell your doctor if you are allergic to povidone (antiseptic), procaine (an anesthetic).
- An MRI or CT scan should be done to make sure there is no pressure-lifting mass in the cranium.
Spinal (lumbar) puncture steps:
Depending on the patient's case, a lumbar puncture may be performed on the patient and discharged (return home the same day) or in the hospital for hospitalized patients, the procedure may be performed by a specialist doctor or nurse.
Lumbar puncture takes around 15-30 minutes.
The patient lies on his left side with both knees raised toward the chin (fetal position), or he can sit and lean forward with the arms and head resting on the table.
First, the skin is cleaned with an antiseptic.
A local anesthetic needle is injected into the lower back to numb the area. You may feel a slight burning sensation when the anesthesia is applied.
A thin, hollow needle (for puncture) is inserted between two lumbar vertebrae, usually between the third and fourth, or fourth and fifth vertebrae (in the lower part of the back between the vertebrae of the lower spine). Gently withdraw the needle. Clean the skin with an antiseptic and cover the lumbar puncture site with a bandage.
After the lumbar puncture:
- The patient should remain in the fetal position for an hour after the lumbar puncture.
- It is recommended to rest and increase fluids intake.
- Avoid strenuous exercise or activities for 24-48 hours.
Complications of lumbar puncture
- Lumbar puncture complications, such as infections and bleeding, are rare, but the conditions of sterilization must be taken completely so that meningitis does not occur.
- The most serious complication is herniation of the brain through the foramen magnum and death.
- Pain on the nerve root pathway or at the puncture site.
- There is no risk of damage to the spinal cord. The spinal cord ends higher than the area of needle insertion in the lumbar spine.
- Some may experience severe pain when sitting or standing.
- The patient may suffer from a prolonged headache.
The pain usually goes away on its own within a couple of days, but it may last for a week or more.
- Some may experience a fast heartbeat (tachycardia), hypotension, nausea…
You should call your doctor if your headache is very painful and lasts more than a few days, or if you feel the following:
- Bloody discharge from the puncture site.
- Signs of inflammation such as fever.
Handling Headache after lumbar puncture
About 10% of patients suffer from a headache after a cerebrospinal fluid puncture, often due to the use of a wide puncture needle or too much fluid puncture. The headache usually begins after a few hours and goes away within a few days.
It can get better with painkillers, drinking water and caffeinated drinks.
Lumbar Puncture Results
The timing of a lumbar puncture result depends on the reason for the test.
If the goal of the test is to diagnose an emergency such as a cerebral hemorrhage (subarachnoid hemorrhage) or meningitis, the results of the test will come in quickly.
In other cases (such as detecting fungi and bacteria), we may get the results of a lumbar puncture within a week.
The laboratory or analyst looks at several factors, including:
- The general appearance of the cerebrospinal fluid: in the normal state it is clear and transparent, and if it becomes cloudy or discolored yellow or red, it can lead us to suspect subarachnoid hemorrhage,
If it turns green, it suspects the presence of an infection in the nervous system or the presence of bilirubin.
- Amount of protein: An elevation of protein in cerebrospinal fluid above a certain threshold (usually 40 mg/dL) can indicate the presence of an infection.
- White blood cells: The cerebrospinal fluid usually contains between 4-5 white blood cells per microliter, and any increase in this value indicates the presence of inflammation or infection.
- The amount of sugar: a decrease in the amount of sugar leads us to suspect an infection in the cerebrospinal fluid.
- Other organelles or cancer cells.
Lumbar Puncture Contraindications
Here are some reasons that are contraindicated for a lumbar puncture:
- Suspicion of a mass in the brain (intracranial hypertension) or a mass in the spinal cord.
- An infection at the puncture site (where the puncture needle entered).
- coagulation disorders.
- Local infection.
- Severe deformity of the spine.
- The patient refused the procedure.
- Low level of consciousness.