A lumbar puncture, also called a spinal tap, is a procedure in
which the fluid surrounding the spinal cord (called the
cerebrospinal fluid or CSF) is withdrawn through a needle and
examined in a laboratory.
This procedure may be performed to:
- Measure the pressure around the brain and spinal cord
- Relieve pressure in the head
- Give spinal anesthesia
- Inject dye for an X-ray diagnostic test
- Inject medication (such as Baclofen)
Testing the CSF can help your doctor diagnose disorders of the
central nervous system (including multiple sclerosis) that may
involve the brain, spinal cord, or their coverings (meninges).
When the CSF is examined in the laboratory, the following are
evaluated:
- The number and types of white blood cells
- The level of glucose
- The types and levels of proteins
- The presence of bacteria, fungi or abnormal cells
How do I prepare for the test?
Maintain your regular
eating schedule. There are no dietary or fluid restrictions before
the test.
Ask your doctor for specific guidelines about discontinuing
alcohol use, aspirin products or anticoagulant medications before
the procedure.
Tell your doctor if you are allergic to Betadine or
Novocaine.
Please make arrangements for transportation, as you should not
drive immediately after the test.
What happens during the test?
You will either lie on
your side with your knees drawn as close to your chest as possible
and your chin toward your chest, or sit with your arms and head
resting on a table.
After cleaning your skin with an antiseptic, sterile cloths
(called drapes) will be placed around the area. A local anesthetic
(pain-relieving medication) will be injected into the area on your
back. You may feel a slight burning sensation. When the area is
numb, a hollow needle is inserted in the lower back between two
lumbar vertebrae. This sometimes causes pressure. The spinal canal
is penetrated, and fluid is collected or medication is injected.
The spinal cord is not touched by the needle during the test.
You may feel some discomfort or have a minor headache.
The needle is removed after the medication has been injected or
fluid has been removed. The area will be cleaned with an antiseptic
and covered with a bandage.
You will lie on your back or stomach for about an hour.
A blood sample will be taken from a vein in your arm and tested,
along with the spinal fluid, in the laboratory. NOTE: if the
procedure was done to inject medication, a blood sample may not be
taken.