What is a Lumbar Puncture (LP)?
A Lumbar Puncture, also known as a spinal tap, can be used to aid in the diagnosis or treatment of diseases of the central nervous system (CNS), which includes the brain and spine. An LP is performed on your lower back, also known as the lumbar region, and hence its name.
During an LP, a thin needle is inserted between the bones in your lower spine to remove a sample of your cerebrospinal fluid. This is the same fluid that surrounds your brain and spine to protect them from injuries and acts as a medium for nutrient transport and waste removal. The fluid sample will then be examined in the lab.
Why may you need a Lumbar Puncture?
A Lumbar Puncture may be done to:
- Collect cerebrospinal fluid for analysis – your cerebrospinal fluid contains glucose, proteins, white blood cells, and other substances in the blood. An examination of the fluid can show the white blood cell count, glucose and protein levels, as well as the presence of bacteria, fungi, or abnormal cells. The presence of red blood cells in your CSF may indicate bleeding.
- Measure the pressure around your brain and spinal cord – which helps to diagnose conditions that may change venous pressure
- Inject medications – such as painkillers, antibiotics, and chemotherapy
- Inject spinal anesthetics – to numb the lower part of the body before an operation or procedure
- Inject dye for an X-ray diagnostic test – which allows doctors to visualize the spinal canal and identify conditions affecting the spinal cord and nerves
- Remove some fluid to relieve pressure in the head – which can help to ease the symptoms of idiopathic intracranial hypertension.
A Lumbar Puncture can help to diagnose:
- Serious viral, bacterial, and fungi infections including meningitis and encephalitis
- Subarachnoid hemorrhage – bleeding in the brain
- Brain or spinal tumors
- Multiple Sclerosis and other inflammatory or auto-immune conditions
- Epilepsy – a brain disorder that involves repeated seizures
- Headaches with unknown causes
- Idiopathic intracranial hypertension (IIH) – a problem caused by elevated cerebrospinal fluid pressure in the brain
- Normal-pressure hydrocephalus (NPH) – the presence of excess fluid in the brain ventricles, which press onto nearby brain tissues
What to do before a Lumbar Puncture?
Before a lumbar puncture, your doctor or healthcare should explain what a lumbar puncture is about and why you need it. Your doctor may request for a CT scan or an MRI scan to check for any swelling in your brain, to ensure that the lumbar puncture is safe for you.
There are no restrictions on dietary and fluid intake before the procedure and you may eat, drink, or take your medications per normal.
Let your doctors and nurses know if you are on any blood-thinning medications, other anticoagulants, or any antibiotics. Do also inform them if you have any allergies to local anesthetics.
What happens during a Lumbar Puncture?
During a lumbar puncture, you will either assume a fetal position – by lying on your side with your knees as close to your chest as possible and your chin tucked in, or a sitting position – by sitting with your arms and head resting on a table.
During the lumbar puncture:
- A local anesthetic is injected into your lower back to numb the puncture site. You may feel a slight burning sensation.
- The doctor will then insert a thin, hollow needle between two bones of your lower spine. This should not be painful but you may feel some pressure in your back.
- Your cerebrospinal fluid will be collected through the hollow needle. You do not need to worry about the needle touching your spinal cord.
- After the procedure is completed, the needle will be removed and a small plaster or bandage will be placed over the puncture site.
How long will it take?
A lumbar puncture usually takes around 30 to 45 minutes, but you will be advised to lie down for at least another hour.
You will be able to go home on the same day if you feel well enough, but do arrange for transport back as you will not be able to drive yourself home.
Care after the procedure
- Plan to rest. Avoid strenuous activities or vigorous exercise for at least a week
- Take pain medication if you need to. Taking some painkillers can help to relieve your headaches or back pain
- Hydrate yourself. Drink lots of water to replenish your fluids
Are there any risks and side effects of lumbar puncture?
A lumbar puncture is generally a safe procedure. However, you may experience some side effects. Common risks that you may face include:
- Headaches. Sometimes, leakage of the cerebrospinal fluid into nearby tissues during a lumbar puncture may cause headaches, which can last up to weeks. For some people, these headaches may be accompanied by nausea and vomiting. You may request for painkillers if you need them.
- Swelling and lower back pain at the puncture site. You may experience pain or numbness in your lower back and legs, but this is temporary and the pain should go away on its own within a few days.
- Risk of bleeding. Sometimes, there may be bleeding in the spinal canal when a small blood vessel is pierced. However, there is no need to worry about it and no treatment is required.
- Risk of infection. There is usually a low risk of infection.
You may be affected by other risks depending on your personal medical condition. Do talk to your healthcare provider to discuss any concerns before the procedure.