Spinal Tap

A procedure to collect cerebrospinal fluid (CSF). It involves inserting a needle between the third and fourth lumbar vertebrae in the back and extracting a sample of fluid.

Parts of the Body Involved

The third and fourth lumbar vertebrae

Reasons for Procedure

Cerebrospinal fluid is withdrawn through a spinal tap and analyzed when the following conditions are suspected:
  • Meningitis (inflammation of the membranes that cover the brain and spinal cord)
  • Encephalitis (inflammation of the brain)
  • Guillain-Barr

Risk Factors for Complications during the Procedure

  • A local infection at the site where the needle would be inserted
  • Elevated pressure in the skull

What to Expect

Prior to Procedure
  • Possibly, a CT scan

Outcome

Based on the pressure and contents of the CSF, a diagnosis can often be made. High pressure can indicate swelling, bleeding, a tumor, or hydrocephalus. The CSF is also analyzed for antibodies, bacteria, viruses, fungi, blood, cancer cells, excess protein, and white blood cells. Normal cerebrospinal fluid is clear and contains no blood. If there is blood or a yellowish color is present, it may indicate spinal cord obstruction or bleeding in the brain or spinal cord.

Call Your Doctor If Any of the Following Occurs

  • Severe headache or headache lasting for more than 24 hours
  • Signs of infection, including fever and chills
  • Redness, swelling, increasing pain, bleeding, or discharge from the site of the spinal tap
  • Tingling
  • Numbness or pain in your lower back and legs
  • Problems with urination