Lumbar Puncture

What is a lumbar puncture? 

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A lumbar puncture (or spinal tap as it is also known) is the insertion of a needle between two lumbar bones (vertebrae) to collect a sample of cerebrospinal fluid, the fluid that surrounds the brain and spinal cord to protect them from injury. A lumbar puncture procedure is performed in the lower back, the lumbar region.

A lumbar puncture procedure helps diagnose serious infections: such as, meningitis; disorders of the central nervous system, for instance, Guillain-Barre syndrome and multiple sclerosis; and cancers of the brain or spinal cord. A lumbar puncture procedure can even, sometimes, be used to inject anaesthetic medications or chemotherapy drugs into the cerebrospinal fluid.

The essence for a lumbar puncture

A lumbar puncture procedure may be carried out to:

• Collect cerebrospinal fluid for laboratory analysis.
• Measure the pressure of cerebrospinal fluid to diagnose a condition.
• Inject spinal anaesthetics, chemotherapy drugs, antibiotics and other medications.
• Inject dye (like myelography) or radioactive substances (such as cisternography) into cerebrospinal fluid to create diagnostic images of the fluid’s flow.
• Take out some fluid to reduce the pressure in the skull or spine.

A lumbar puncture procedure can be helpful in the diagnosis of several diseases and disorders. Such as;

• Meningitis: An inflammation of the membrane covering the brain and spinal cord, due to viral, bacterial or fungal infection.
• Encephalitis: An inflammation of the brain, caused by virus.
• Some cancers relating to the brain and spinal cord.
• The cause of bleeding in the subarachnoid space, that is, the area between the brain and the tissues that cover it.
• Reye syndrome.
• Myelitis: An inflammation of the spinal cord or the bone marrow.
• Neurosyphilis. 
• Guillain-Barré syndrome. 
• Demyelinating diseases. 
• Headaches of unknown cause.
• Pseudotumour cerebri (also known as idiopathic intracranial hypertension, or IIH).
• Normal pressure hydrocephalus.

Preparation for lumbar puncture 

• Before a lumbar puncture procedure, a review of medical history and physical examination will have to be done. 
• Blood tests will also be carried out to check for bleeding or clotting disorders. 
• A CT scan or MRI will be recommended to check for any abnormal swelling in or around the brain.
• Specific instructions will be given by the healthcare professional as regards food, drink and medications.

Lumbar puncture procedure

The first thing to do will be to change into a hospital gown. Although, in some cases, it may not be necessary. 

There are a few likely positions for a lumbar puncture procedure. Generally, one lies on either of side with the knees drawn up to the chest. One may also have to sit and lean forward on a stable surface. These positions flex the back, widen the spaces between the vertebrae and make it easier for the insertion of the needle. For an infant or a kid, someone will have to hold the child in position during the procedure.

After positioning, the back is washed with an antiseptic soap or iodine and covered with a sterile sheet. Local anaesthesia is injected into the lower back to numb the puncture site before inserting the needle. The local anaesthesia will briefly sting as its being injected.

A skinny hollow needle is inserted between the two lower vertebrae, through the spinal membrane and into the spinal canal. The cerebrospinal fluid pressure is first measured. A small amount of the fluid is then withdrawn, and the pressure is re-measured. The needle is then removed, and the site of the puncture is covered up with a bandage.

The procedure usually lasts around 45 minutes. –

The aftermath of a lumbar puncture procedure

The aftermath of a lumbar puncture procedure requires enough rest. It is best advised not to participate in strenuous activities on the day of the procedure. Pain medication may be needed to combat the pain from the procedure.

Lumbar puncture results 

The cerebrospinal fluid sample collected is sent to the laboratory for analysis. Findings will be discussed by the doctor. 

FAQs

What are the merits of lumbar puncture?

A lumbar puncture is a technique that helps to accurately diagnose or rule out certain medical conditions, of which some may be life-threatening illnesses. Therefore, the quicker the diagnosis, the sooner appropriate treatment can be given. Some of these conditions, such as bacterial meningitis, can be really fatal if prompt treatment is not given.

A lumbar puncture can also help a doctor design an appropriate treatment plan and prescribe some types of medication.

What are possible lumbar puncture side effects?

Though generally acknowledged as safe, there are a couple of lumbar puncture side effects. Some of which are;

• Post lumbar puncture headache.
• Back pain or discomfort.
• Bleeding near the puncture site or, rarely, in the epidural space.
• Brainstem herniation; increased pressure within the skull (intracranial).

What is cerebrospinal fluid? 

The cerebrospinal fluid is the fluid found in the central nervous system surrounding the brain and spinal cord. This fluid acts as a support of buoyancy for the brain and the spinal cord. This support also protects the brain from injury.

What is the normal range of cerebrospinal fluid?

Normal values from cerebrospinal fluid examination should be as follows:

• Protein 15 to 60 mg/dl.
• Glucose 50 to 80 mg/dl.
• Cell count 0 to 5 mononuclear cells.
• Initial pressure 70 to 180mm.

What are useful tips for lumbar puncture recovery?

There are some dos and don’ts of lumbar puncture recovery:

Dos

• Drink plenty of fluids, water preferably.
• Take painkillers, such as paracetamol, to ease the pain you may experience.
• Lie down instead of sitting upright.

Don’ts

• Drive or operate machinery for at least 24 hours.
• Play a sport or do any strenuous activities for a week, at least.

How long does a lumbar puncture take?

A lumbar puncture takes about 30 to 45 minutes, after which one stays lying down at the hospital for at least another hour while the nurses keep an eye.

What is the outlook?

Your long-term outlook from a lumbar puncture depends on the final diagnosis.