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Lumbar Puncture - Indications, Procedure, and Possible Outcomes of the Study

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A lumbar puncture is a diagnostic and therapeutic procedure where the doctor accesses spinal canal with a needle to draw cerebrospinal fluid or inject drugs.

Written by

Dr. Jayasree S

Medically reviewed by

Dr. Abhishek Juneja

Published At September 7, 2022
Reviewed AtSeptember 7, 2022

What Is a Lumbar Puncture or Spinal Tap?

It is a procedure where the doctor inserts a thin hollow needle into the lower back region of the spine to extract a clear fluid known as the cerebrospinal fluid (CSF). The brain and spinal cord are suspended and protected in a pool of clear fluid known as the cerebrospinal fluid. It nourishes and provides cushioning to the delicate nerve structure. When an infection, cancer, or other abnormalities are suspected in the brain, its outer covering (meninges), or the spinal cord, the doctor may conduct a lumbar puncture and get a sample of the CSF. With appropriate tests and observation of CSF, one can confirm the diagnosis.

When Does an Individual Undergo a Lumbar Puncture?

Following are the indications for conducting a lumbar puncture:

  • When the individual shows the signs and symptoms of meningitis (inflammation of the outer layers of the brain) or encephalitis (infections that affect the brain), it could be a bacterial, viral, or fungal infection.

  • When one is suspected of having bleeding in and around the brain (subarachnoid hemorrhage).

  • To check for conditions like myelitis, multiple sclerosis, Reye syndrome, or Guillain -Barre syndrome.

  • When the individual shows an altered mental status and underlying cause is not known.

  • When one has a long-standing headache of unknown cause.

  • To check for the presence of cancers in the brain or spinal cord. Also, to see if cancers from other parts of the body have invaded the nervous system.

  • To measure the CSF pressure on the brain. If required, some of the fluid is drained to relieve the excess pressure (intracranial hypertension).

  • For injecting an anesthetic medicine into the spinal cord area for surgical procedures.

  • For injecting medications like chemotherapy drugs (intrathecal chemotherapy).

  • For injecting chemicals known as contrasting dyes for conducting certain imaging studies (myelography).

How Is a Lumbar Puncture Procedure Performed?

The lumbar puncture procedure takes around fifteen to thirty minutes. First, the health care provider will explain the procedure clearly and obtain informed consent from the patient or the bystanders. One is asked to sit up and lean forward or lie down with knees curled towards the chest and head bent downward. The spaces between each bone of the spine (vertebrae) are the widest in these positions, which helps with the easy insertion of the needle. One must stay very still throughout the procedure.

The skin over the area is cleaned and anesthetized to reduce any discomfort. The doctor inserts a spinal needle through the spaces between the bones until it enters the spinal column. Sometimes an imaging method like an ultrasound scan is used to guide the doctor on the proper insertion of the needle. Once it reaches the space containing the CSF, a small amount of the fluid is drawn out. As per the requirement, procedures like draining out the CSF for relieving pressure or injecting medicines are also conducted. Then the doctor withdraws the needle and places a bandage on the spot of the injection. After the test, one is advised to lie back and rest for a while and drink plenty of fluids.

What Are the Possible After-Effects of a Lumbar Puncture?

Rarely the lumbar puncture procedure may be followed by a few side effects. One is advised to contact the doctor if any of the following symptoms worsen:

  1. The most common problem is a headache that lasts for a few days to weeks. This is due to leakage of CSF from the spot of injection. The headache tends to worsen while sitting up or standing and gets better on lying down.

  2. Some may suffer backaches as well.

  3. Dizziness and temporary tingling, pain, or numbness down the legs.

  4. Difficulty in urinating.

  5. Nausea and vomiting.

  6. Infection at the injection site.

  7. Accidental leaking of blood into the spinal canal.

What Are the Outcomes of a Lumbar Puncture and CSF Study?

The CSF sample extracted through a lumbar puncture is taken for laboratory examination, and the doctor can decide on the treatment based on the results. The possible outcomes can be:

  • Examining the CSF for the levels of glucose, proteins, cloudiness, and white blood cells can confirm or discard the presence of an infection.

  • The sample is examined for the presence of microorganisms like bacteria, viruses, or fungi that may have caused an infection.

  • The presence of red blood cells in the CSF shows bleeding in or around the brain.

  • The presence of cancer cells can confirm the individual is affected by some type of malignant brain tumor.

  • Increased levels of CSF pressure may be indicative of bleeding or inflammation in the head.

When Should One Avoid Undergoing a Lumbar Puncture?

Lumbar puncture should not be conducted in an individual who has issues with bleeding, clot formation, and low platelet count. Those who are taking blood-thinning medications should seek the doctor’s advice about stopping the drug before undergoing the procedure. If a massive infection of the brain is suspected, spinal tapping should not be done. Also, when there is some form of infection in the site of lumbar puncture, there are chances for it to spread over to the CSF and lead to complications. Allergy to local numbing medicines and pregnancy are two other conditions where the lumbar puncture is avoided.

Conclusion:

A lumbar puncture procedure is always performed after looking at the medical history and conducting a thorough clinical examination of the patient. One may order additional lab tests to check for bleeding and clotting disorders. Lumbar puncture is always accompanied by computed tomography (CT) scan or magnetic resonance imaging (MRI) studies to understand the disease condition better. It is a valuable diagnostic aid for several neurological conditions. A qualified medical practitioner may decide what suits one the best.

Frequently Asked Questions

1.

What Is the Anatomical Location of a Lumbar Puncture?

A thin, hollow spinal needle is inserted into the lumbar spine at the level of L3 to L4 or L4 to L5. The layers penetrated by the spinal needle include supraspinatus ligaments, interspinous ligaments, ligamentum flavum, epidural space, dura, and subarachnoid membrane into subarachnoid space.

2.

What Is the Purpose of Lumbar Puncture?

The lumbar puncture is usually performed to find out the following:
- Meningitis.
- Subarachnoid hemorrhage.
- Therapeutic relief of pseudo motor cerebri.
- Guillain barre syndrome and carcinomatous meningitis.

3.

What Are the Instructions to Follow After Lumbar Puncture?

The lumbar puncture procedure takes about 30 to 45 minutes. Patients are advised to lie flat on their back, side, or stomach for at least four to six hours. The blood pressure, puncture site, and vitals will be monitored in the hospital after the procedure. It is important to keep your head and back flat after going home.

4.

Can Lumbar Puncture Diagnose MS?

Lumbar puncture is the first step in diagnosing multiple sclerosis. It is a common and simple procedure for determining multiple sclerosis. However, it is not a confirmatory test; the doctor may advise several other tests to confirm multiple sclerosis.

5.

What Are the Side Effects of Lumbar Puncture?

The adverse effects of lumbar puncture include headache. Headache is due to leakage of fluid into the surrounding tissues. About 25 percent of people experience this side effect of headache, and it starts several hours after the procedure and lasts up to two days. It is associated with nausea, vomiting, and diarrhea.

6.

What Is Post-lumbar Puncture Syndrome?

Post-lumbar puncture syndrome is the most common complication of lumbar puncture. It involves continuous leaking of cerebrospinal fluid due to the perforation of the dura mater and intracranial hypotension.

7.

What Are the Conditions That Lumbar Puncture Diagnose?

Lumbar puncture helps to diagnose:
- Bacterial, fungal, and viral infections such as meningitis, encephalitis, and syphilis.
- Subarachnoid hemorrhage.
- CNS cancers.
- Demyelinating diseases.

8.

How Is Lumbar Puncture Used to Diagnose Dementia?

An abnormal cluster of proteins called amyloid and tau in the brain is the feature of Alzheimer's disease. These abnormal changes are also seen in the proteins of cerebrospinal fluid (CSF). Therefore, the lumbar puncture can diagnose dementia or Alzheimer's disease.

9.

Are a Spinal Tap and a Lumbar Puncture the Same?

There is no difference between a spinal tap and a lumbar puncture. Spinal tap is another name for lumbar puncture used to identify certain health conditions.

10.

What Are the Contraindications Before a Lumbar Puncture?

Avoid eating or drinking three hours before the day of the procedure. The doctor may advise you to stop Aspirin, nonsteroidal inflammatory drugs (NSAIDs), and blood thinners several days before the procedure

11.

When the Lumbar Puncture Is Recommended?

The lumbar puncture is contraindicated in patients having coagulation disorders with active bleeding, thrombocytopenia, or having internalized normal ratio, INR>1.4, without treating the underlying abnormalities and infection over the puncture site.
Dr. Abhishek Juneja
Dr. Abhishek Juneja

Neurology

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cerebrospinal fluidlumbar puncture
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