Lumbar Puncture

1 What is a Lumbar Puncture (Spinal Tap)?

Here you can find out more about a lumbar puncture (spinal tap) procedure.

In the lumbar region, a spinal tab is performed in your lower back. A needle is inserted between two lumbar bones or vertebrae to remove a sample of cerebrospinal fluid during the lumbar puncture.

The cerebrospinal fluid is the fluid that surrounds your brain and spinal cord to prevent them from injury.

This can also help diagnose serious infections such as meningitis, cancers if the spinal cord and brain, and other disorders of the central nervous system such as multiple sclerosis.

2 Reasons for Procedure

Lumbar puncture may be done for the following reasons:

  • Measures the pressure of your cerebrospinal fluid.
  • Collect cerebrospinal fluid for laboratory analysis.
  • Inject dye (myelography) or radioactive substances (cisternography) into cerebrospinal fluid to make diagnostic images of the flow of the fluid.
  • Inject spinal anesthetics, chemotherapy drugs, and other medications.

The information can help diagnose:

3 Potential Risks

Lumbar puncture (spinal tap) can carry some risks such as:

  • Post-lumbar a puncture headache due to a leak of fluid into nearby tissues which can be accompanied by nausea, dizziness, and vomiting, this can last from a few hours to few weeks.
  • Back pain or discomfort such as feeling tenderness or pain in your lower back up to the back of your legs.
  • Bleeding near the puncture site or into the epidural space.
  • Brainstem herniation after a sample of the fluid is removed.

To determine if there is evidence of a space-occupying lesion that results in increased intracranial pressure, your doctor will order a computerized tomography (CT) scan or MRI.

4 Preparing for your Procedure

In preparing for your lumbar puncture (spinal tap), you must follow your doctor’s orders. 

Your doctor asks questions about your medical history, does a physical exam, and orders blood tests to check if you have any bleeding or clotting disorders before your lumbar puncture.

Your doctor may also suggest MRI or CT scan to check for any swelling.

Talk to your doctor if you are taking any blood-thinning medications or if you are allergic to any medications.

5 What to Expect

Here’s what you can expect before, during, and after your lumbar puncture (spinal tap).

Your doctor will ask you to change into a hospital gown and the procedure is done in a hospital. He will ask you to lie on your side with your knees drawn up to your chest so it will make it easier for your doctor to insert the needle. Your back will be washed and covered with a sterile sheet.

During the procedure, you will be injected with anesthesia to numb the puncture site at your lower back. A thin, hollow needle is inserted between the two lower vertebrae (lumbar region), through the spinal membrane (dura) and into the spinal canal.

You may feel pressure in your back during this part of the procedure. You will be asked to change position once the needle is in place. The pressure will be measured again the needle is removed while the puncture site will be bandaged.

Your doctor will advise you to rest and do not participate in strenuous activities after the procedure; your doctor may tell you when the right time to go back to your job is. To help reduce pain and headache, your doctor will prescribe a nonprescription pain-relieving medication that contains acetaminophen.

6 Procedure Results

Understanding the results of your lumbar puncture (spinal tap) will be made possible by your doctor.

The samples of your spinal fluid will be sent to the laboratory to check it for:

  • General appearance because if it is cloudy yellow or pink in color means infection.
  • Total protein and the presence of certain proteins greater than 45 milligrams means there is an infection or inflammatory condition.
  • White blood cells to check if it increased because it means infection.
  • Sugar or glucose because low glucose level may indicate infection or other condition.
  • Microorganisms to check if there is the presence of viruses, fungi, bacteria, or pother microorganisms.
  • Cancer cells such as a tumor or immature blood cells.

To help establish a possible diagnosis, lab results are combined with information obtained during the test, such as spinal fluid pressure. Your doctor will tell you when the result is coming out.

You can ask questions to your doctor such as:

  • What are my next steps based on my results?
  • Do I need follow-up?
  • Will I need to repeat the test at some point?
  • Are there any factors that might have affected the results of this test and, therefore, may have altered the results?