A lumbar puncture (spinal tap) is a medical procedure in which a healthcare professional extracts cerebrospinal fluid from the spine for diagnostic purposes. A local anaesthetic is administered during the procedure so the patient does not feel any pain.

This test helps identify severe conditions that affect the brain, spinal cord, and nerves, such as leukaemia, meningitis, and encephalitis. Understanding this condition is important for early detection of underlying health issues and choosing the right treatment. 

It is also helpful for MBBS and NEET PG students, as it is an essential topic in their studies. This guide explores the procedures, uses, risks, and treatment options for lumbar punctures. Keep reading for detailed insight into this procedure.

 What is a Lumbar Puncture?

A lumbar puncture (spinal tap) is a medical test used to diagnose certain health conditions. It is carried out in the lower back (lumbar region), where a needle is inserted between two lumbar vertebrae to remove a sample of cerebrospinal fluid, the protective fluid surrounding the brain and spinal cord.

This procedure helps detect serious infections such as central nervous system disorders and meningitis such as Guillain-Barré syndrome and multiple sclerosis. It can also be used to diagnose bleeding around the brain or cancers affecting the brain and spinal cord.

In some cases, a lumbar puncture is performed to inject anaesthetic medication or chemotherapy directly into the cerebrospinal fluid.

Why is a Lumbar Puncture Performed?

A lumbar puncture is performed for several reasons, the most common being to collect cerebrospinal fluid (CSF) for testing through lumbar puncture needle parts. This helps diagnose numerous conditions by examining red and white blood cells, glucose levels, protein, colour, and clarity.

The fluid is also tested for viruses, bacteria, or abnormal cells. In some cases, excess CSF is removed when there is an overproduction or reduced absorption of the fluid.

Conditions Diagnosed with a Lumbar Puncture

A lumbar puncture can help identify:

• Meningitis

Inflammation of the brain and spinal cord membranes is usually caused by an infection.

• Encephalitis

Brain inflammation is often due to a virus.

• Brain and Spinal Cord Cancers

Certain types of cancer affect the central nervous system.

• Subarachnoid Haemorrhage

Bleeding between the brain and its surrounding tissues.

• Reye Syndrome

A rare but serious disease that affects the brain and other organs, sometimes linked to aspirin use in children.

• Myelitis

Swelling of the bone marrow or spinal cord.

• Neurosyphilis

A phase of syphilis in which bacteria infect the central nervous system.

• Guillain-Barré syndrome

A disorder where the immune system attacks the nervous system.

• Demyelinating diseases

Conditions such as multiple sclerosis, where the protective coating of nerve fibres is damaged.

• Unexplained Headaches

Used to diagnose certain inflammatory conditions after imaging and evaluation.

• Pseudotumor Cerebri (IIH)

A condition with increased pressure in the subarachnoid space, with unclear causes.

• Normal Pressure Hydrocephalus

A rare condition in older adults causing loss of bladder control, memory issues, and difficulty walking.

Uses of a Lumbar Puncture

A lumbar puncture is performed for several uses or purposes, which include:

• Measuring CSF pressure
• A special tube called a manometer is used during the procedure.
• Injecting medications into the spinal cord, including:

• Spinal anaesthesia for surgery
• Contrast dye for X-ray tests like myelography
• Chemotherapy drugs for cancer treatment

A healthcare provider may recommend a lumbar puncture for other medical reasons, depending on the patient’s condition.

Risks of a Lumbar Puncture

A lumbar puncture is generally a safe procedure, but it does come with certain risks, including:

• Post-lumbar Puncture Headache

Due to fluid leakage, around 25% of people may develop a headache after the lumbar puncture procedure. This headache can start within a few hours or up to two days later and may be accompanied by vomiting, nausea, and dizziness.

It often worsens when standing or sitting but improves when lying down. These headaches can last from a few hours to over a week.

• Back Pain or Discomfort

Some may experience tenderness or pain in the lower back, which can sometimes spread down the legs.

• Bleeding

There is a small risk of bleeding near the lumbar puncture site or, in rare cases, in the epidural space.

• Brainstem Herniation

If a person has a brain tumour or a space-occupying lesion, removing cerebrospinal fluid (CSF) could increase pressure inside the skull, affecting the brainstem (the part connecting the brain to the spinal cord).

Hence, computed tomography (CT) or magnetic resonance imaging (MRI) scans are sometimes done before the procedure to check for increased pressure or abnormalities to reduce this rare risk. A neurological examination can also help identify potential issues.

How to Prepare for a Lumbar Puncture?

Before a lumber puncture, a healthcare provider may recommend certain preparations, along with a physical examination and a review of medical history. These may include:

• A CT or MRI scan to assess the area before the procedure.
• A blood test to check for any underlying issues.
• Adjusting medications if taking blood thinners like aspirin or warfarin. However, any medication changes should only be made with the provider’s approval.

These steps help ensure the procedure is safe and reduce the risk of complications. The healthcare provider will also provide specific instructions to help with preparation.

What happens during and after a Lumbar Puncture?

The lumbar puncture procedure can be performed either as an outpatient procedure or during a hospital stay. The method may vary depending on the patient’s condition and the healthcare provider’s approach.

Some doctors perform it at the bedside, while others use fluoroscopic guidance (a type of live X-ray) to guide the procedure.

Before the Procedure

• Step 1: The patient must remove jewellery, clothing, or any other objects that might interfere. A hospital gown will be provided.
• Step 2: They will be asked to empty their bladder before the procedure.

During the Procedure

• Step 3: The patient may lie on their side with their chin tucked to the chest and knees drawn up or sit on the edge of the exam table with arms resting on a table in front. These positions help create more space between the vertebrae.
• Step 4: The lower back will be cleaned with an antiseptic solution, and sterile towels will be placed around the area. The healthcare provider will put on clean, sterile gloves.
• Step 5: A local anaesthetic will be given to the patient’s numb area. The injection may cause a brief stinging sensation, but it helps reduce pain during the procedure.
• Step 6: A hollow needle will be inserted through the numbed area into the spinal space to collect cerebrospinal fluid (CSF). The patient may feel pressure, and they must remain still throughout.
• Step 7: Around one tablespoon of CSF will be collected in test tubes. If medication is required to be injected into the spinal canal, it will be done through the same needle after fluid collection.
• Step 8: Once complete, the needle will be removed, and a bandage will be applied to the injection site. The fluid samples will be sent to the lab for testing.
• Step 9: The patient should inform the healthcare provider immediately if they experience numbness, headache, tingling, or dizziness during the lumbar puncture procedure.

After the Procedure

• Step 10: The patient will be advised to lie flat for some time to reduce headaches, though rolling from side to side is usually allowed.
• Step 11: Extra fluids should be consumed to help replenish the CSF and lower the risk of headaches.
• Step 12: Depending on the recovery, the patient may either return to their hospital room or be discharged home. If discharged, they should rest for the remainder of the day.

How to Recover from a Lumbar Puncture?

Recovery from a lumbar puncture usually takes a few days, but for some people, it may take longer. Several ways can help the recovery process.

• Patients should take a minimum of 24 hours of rest following the procedure.
• They should drink plenty of fluids to help replenish the lost cerebrospinal fluid.
• If experiencing a headache, they must try lying flat on the back to ease discomfort.
• They can take paracetamol to relieve headaches or pain.
• The patient must avoid physical work, heavy lifting, or sports until fully recovered.

Side Effects of a Lumbar Puncture?

After the procedure, some common side effects may occur, including:

• Headache
• Back pain
• Bleeding or clear fluid leakage from the injection site
• Swelling at the puncture site

These effects do not last long and usually disappear in a few days.

Possible Complications of a Lumbar Puncture

A lumbar puncture is generally a safe procedure, but in rare cases, complications can occur, such as:

• Long-term back pain
• Infection
• Hearing loss
• Double vision
• Blood clots
• Nerve damage, leading to persistent pain, numbness, or tingling in the legs or arms

If the procedure is unsuccessful, a repeat appointment may be required.

What do Lumbar Puncture Results Show?

After a lumbar puncture (spinal tap), the spinal fluid collected via the lumbar puncture needle is sent to a laboratory for testing. Lab specialists check several factors to help diagnose possible conditions.

Here are some of the main factors examined:

• Appearance

Healthy spinal fluid is colourless and clear. If it appears yellow, orange, or pink, it may indicate bleeding. A green colour could suggest an infection or the presence of bilirubin.

• Protein Levels

Total protein is measured, and high levels (above 45 mg/dL) may indicate inflammation or infection. Specific values can vary between laboratories.

• White Blood Cells

Normally, the spinal fluid contains up to five white blood cells per microliter. Higher levels may indicate an infection or another medical condition.

• Glucose (Sugar)

Low glucose levels in the fluid may suggest an infection, tumour, or other disorder.

• Microorganisms

The presence of viruses, bacteria, fungi, or other microorganisms may confirm an infection.

• Cancer Cells

If tumour cells or immature blood cells are found, this may indicate certain types of cancer.

When will the Test Results be Available?

The test results of the lumbar puncture site are generally combined with other findings, such as spinal fluid pressure, to assist in making a diagnosis. 

Healthcare providers usually share results within a few days, though sometimes it may take longer. It is advisable to ask when to expect the results.

 FAQs about Lumbar Puncture

1. Where is a lumbar puncture performed?

 A lumbar puncture is usually done either in a hospital or a medical clinic. In many cases, it is an outpatient procedure, meaning the patient can go home the same day. If this is the case, someone should be available to drive them home after the test.

2. Is a person asleep during a lumbar puncture?

No, general anaesthesia is not used for this procedure. Instead, a local anaesthetic is given to numb the area so the person remains awake but does not feel any pain.

3. How long does a lumbar puncture take?

The entire procedure usually lasts between 15 and 30 minutes. However, the lumbar puncture needle is usually only in place for a few minutes.

4. What happens after a lumbar puncture?

After a lumbar puncture, a healthcare provider will give instructions on how to take care of oneself. These may include:

• The patient should not drive or operate heavy machinery for 24 hours.
• They should lie on the back or side for at least one to a few hours.
• They must avoid intense physical activities or exercise for 24 to 48 hours.
• They must take enough rest.
• They must drink plenty of fluids to stay hydrated.

If approved by the healthcare provider, returning to work may be possible after the procedure.

5. Are headaches common after a lumbar puncture?

Around 10% of people who have a lumbar puncture may develop a spinal headache. This causes severe pain, especially when standing or sitting. The headache can appear within hours or a few days after the procedure. It usually goes away on its own in a few days but may last a week or more. Other possible symptoms include:

• A fast heart rate (tachycardia).
• Low blood pressure (hypotension).
• Nausea.

Drinking plenty of fluids, taking over-the-counter pain relief, and consuming caffeinated drinks may help ease the discomfort.

6. What happens if the results are abnormal?

Since a lumbar puncture needle can help diagnose numerous conditions affecting the nerves, brain, and spinal cord, the next steps depend on the results. 

For example, a high white blood cell count may indicate an infection, which can be treated with antibiotics. A healthcare provider will explain the results and discuss the necessary steps for treating any underlying conditions.

 Conclusion

The idea of inserting a needle into the spine may seem worrying, but a lumbar puncture, also called a spinal tap, is a low-risk procedure. There is no pain during the procedure, though some pressure may be felt in the lower back.

Anyone with concerns before, during, or after the lumbar puncture procedure should speak with their healthcare provider. If a spinal headache develops, the provider can suggest ways to relieve it.

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