Lumbar puncture is a medical procedure for analyzing cerebrospinal fluid. During it, a needle is inserted into the spinal canal in the lumbar region to take a sample of the fluid surrounding the spinal cord, which is then examined in a laboratory.
What is a diagnostic lumbar puncture?
A lumbar puncture involves inserting a needle into the lower back to obtain a sample of cerebrospinal fluid and indirectly measure intracranial pressure (ICP).
Cerebrospinal fluid (CSF) is a clear fluid surrounding the brain and spinal cord. It has several functions. It acts as a cushion to protect the central nervous system from bruises and shocks, as a source of nutrition, and as a way to rid the nervous system of waste.
The sample taken from this fluid is sent to the laboratory for examination and analysis to investigate:
- The presence of bacteria, fungi, or abnormal cells.
- Glucose (sugar) levels in it.
- Types and levels of proteins.
- Types and numbers of white blood cells.
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The doctor requests a lumbar puncture of the CSF for diagnostic and therapeutic purposes in some medical cases:
- In the event of a brain hemorrhage (intracranial hemorrhage).
- Dementia.
- Leukemia or other types of cancer.
- Diagnosis of various nervous system diseases such as meningitis, encephalitis, and spinal cord inflammation.
- To investigate multiple sclerosis or other autoimmune diseases (Guillain-Barré syndrome).
- To diagnose and treat high pressure of the cerebrospinal fluid.
- It may also be used to perform spinal anesthesia (for example, before childbirth) to numb the lower part of the body.
- Injection of cancer treatments.
- Injection of dye (contrast material) in radiography.
Lumbar puncture steps
To perform a lumbar puncture, we must ensure that the area is completely sterile and follow the following steps:
Before the lumbar puncture
- A blood clotting time test may be requested before the lumbar puncture to ensure it is normal.
- Stopping blood thinners in someone who needs a spinal tap, such as aspirin or warfarin.
- Tell your doctor if you are allergic to povidone (an antiseptic) or procaine (an anesthetic).
- An MRI or CT scan should be performed to ensure that no mass is raising pressure in the skull.
Spinal tap (lumbar) steps
Depending on the patient’s condition, the patient may be given a lumbar puncture and discharged (returning home the same day) or in the hospital. For hospitalized patients, the procedure is performed by a doctor or a specialized nurse.
The lumbar puncture takes 15-30 minutes.
The patient lies on his left side with his knee raised towards the chin (fetal position), or he can sit and lean forward with his arms and head supported 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, and you may feel a slight burning sensation when the anesthesia is applied.
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A thin, hollow needle (specially designed for lumbar puncture) is inserted between two lumbar vertebrae, usually between the third and fourth or fourth and fifth vertebrae (in the lower back, between the vertebrae of the lower spine). The doctor feels a slight pressure when the needle is inserted. The fluid is removed, or the medicine is injected, and then the needle is gently withdrawn. The skin is cleaned with an antiseptic, and the lumbar puncture site is covered with a bandage.
After the lumbar puncture
- You should remain in the fetal position for an hour after the lumbar puncture.
- Rest and plenty of fluids are recommended.
- Avoid strenuous exercise or activity for 24-48 hours.
Complications of lumbar puncture
- Complications of lumbar puncture, such as infections and bleeding, are rare, but sterilization conditions must be fully observed to avoid meningitis.
- The most severe complication is brain herniation through the foramen magnum and death.
- Pain along the nerve root path or at the puncture site.
- There is no risk of damage to the spinal cord; the spinal cord ends above the point where the needle is inserted in the lumbar spine.
- Some people may experience severe pain when sitting or standing.
- The person undergoing the procedure may experience a prolonged headache.
- The pain usually disappears within two days, but it may last a week or more.
- Some people may experience rapid heartbeat (arrhythmia), low blood pressure, nausea…
You should contact your doctor if your headache is excruciating and lasts for more than a few days or if you experience:
- Blood discharge from the puncture site.
- Signs of infection such as fever.
Treatment of headaches after a lumbar puncture
About 10% of patients experience headaches after a lumbar puncture, often due to the use of a wide puncture needle or the puncture of fluid that is too large. The headache usually starts after a few hours and disappears within a few days.
Painkillers, drinking water, and drinks containing caffeine help with this.
Lumbar puncture results
The timing of getting the lumbar puncture result depends on the reason for the test.
If the test is to diagnose an emergency condition, such as a brain hemorrhage (subarachnoid hemorrhage) or meningitis, the results will appear quickly.
In other cases (such as detecting fungi and bacteria), we may get the lumbar puncture results within a week.
The laboratory or analyst looks at several factors, which are:
- The general appearance of the cerebrospinal fluid: It is usually clear and transparent, and if it becomes cloudy or yellow, or red, it may indicate a subarachnoid hemorrhage; if it turns green, there is a suspicion of a nervous system infection or the presence of bilirubin.
- The amount of protein: An increase in protein in the cerebrospinal fluid above a specific limit (usually 40 mg/dL) may indicate the presence of an infection or inflammation.
- White blood cells: Cerebrospinal fluid usually contains 4-5 white blood cells per microliter, and any increase in this value indicates inflammation or infection.
- Sugar quantity: Low sugar quantity leads us to suspect infection in the cerebrospinal fluid.
- Other organs or cancer cells.
Contraindications for lumbar puncture
Here are some reasons that are contraindications for performing a lumbar puncture:
- Suspicion of a mass in the brain (increased intracranial pressure) or a mass in the spinal cord.
- Infection at the puncture site (where the puncture needle is inserted).
- Coagulation disorders.
- Local infection.
- Severe spinal deformity.
- The patient refuses the procedure.
- Decreased level of consciousness.
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You can contact us to learn more about diagnostic and therapeutic spinal taps and their complications and risks.
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