Lumbar Puncture

What is lumbar puncture? ​

It is a minor bedside procedure to collect a sample of fluid that surrounds the spinal cord (cerebrospinal fluid or CSF)). A thin, hollow needle is inserted into your lower back and CSF is withdrawn. The point of insertion would be made numb with a local anaesthetic agent to minimise pain. You are conscious throughout the procedure.

A lumbar puncture is performed to:

• Examine your spinal fluid for signs of infection e.g. meningitis (an infection of the tissues surrounding the brain and spinal cord
• Detect bleeding in the space around the brain that is not detected by a computered tomography (CT) scan
• Detect an increase or reduction in intracranial pressure
• Diagnose inflammation of the tissues surrounding the brain and spinal cord such as multiple sclerosis in Guillain-Barre syndrome

​Is this a common procedure?

Yes. From a medical point of view, it is a relatively simple procedure yet a powerful diagnostic tool to help your doctor diagnose your condition and select the appropriate treatment. This procedure is usually done at your bedside, and in some instances at the x-ray department.

What are the risks involved?

Pain during placement

• Discomfort can result from the needle puncture. This will be lessened with a local anaesthetic. The discomfort is usually mild and transient and does not imply serious injury.

Headache

• Some patients get a headache. This is usually mild and improves with bed rest and hydration.

Bleeding

• Bleeding can occur around the puncture site or, rarely, into the spinal cord. This is usually minor and stops on its own.

Coning

• This is a downward shift of the brain due to a sudden decrease in the pressure within the intra-cranial cavity. This is exceedingly rare and occurs when lumbar puncture is inappropriately done without due consideration of raised intra-cranial pressure.

What happens during the procedure?

You will be asked to lie on your side in a curled-up position, with your chin and knees tucked into your chest. In this position, the space between the vertebrae of your lower spine is increased so that it would be easier to thread in the thin needle.

Next, the doctor chooses the insertion site, which is between the L4 and L5 vertebrae at your lower back.

• The puncture area is cleaned and draped with sterile towels
• A local anaesthetic (numbing medicine) is injected into your skin to minimise your discomfort
• The spinal needle is inserted
• Your doctor will measure the CSF pressure and withdraw a sample to be sent to the laboratory for analysis
• A small sterile dressing is then placed over the puncture site

After the procedure, you should lie on your back to rest for a period until you feel well enough to get up.

Frequently asked questions (FAQ)

Can I eat or drink or take my medications before this procedure?

• Fasting is not necessary. You may continue taking your medications as directed.

How do I prepare for this test?

• Try to relax. During and before the procedure, you should try to breathe slowly and deeply. You should not hold your breath, strain, move, or talk. You will be "coached" during the procedure by your doctor.

Glossary

Cerebrospinal fluid

• A clear colourless liquid that cushions and protects the brain and spinal cord. It flows freely within the ventricles and the subarachnoid space. Under normal conditions, you have about a half cup of CSF. Your body is constantly producing CSF. The entire CSF volume is replaced every 6 to 8 hours

Intracranial pressure

• Pressure exerted by the cerebrospinal fluid or brain matter within the skull

Ventricles

• Cavities within the brain containing CSF

Subarachnoid space

• CSF-filled area between the brain/spinal cord and the tissue covering these structures