What is the primary purpose of performing a spinal tap (lumbar puncture)?

• A. To sample CSF to test for meningitis, blood, or abnormal pressure
• B. To measure brain activity with EEG
• C. To image the brain with MRI
• D. To remove CSF for transplantation

Answer: (A)

Collecting cerebrospinal fluid through a lumbar puncture is done to sample CSF for diagnostic testing. Analyzing the fluid allows clinicians to detect meningitis by looking for infection signs such as white blood cells, pathogens, or abnormal protein and glucose levels; to identify blood in the CSF indicating a subarachnoid hemorrhage; and to measure opening pressure to assess intracranial pressure. This procedure also enables other CSF tests when needed. It's not used to measure brain electrical activity, which is the realm of EEG, nor to image the brain, which is MRI, and removing CSF for transplantation is not a standard purpose of this procedure.