What is the primary purpose of performing a lumbar puncture?

• A. To obtain a sample of cerebrospinal fluid for meningitis testing.
• B. To measure brain electrical activity.
• C. To drain CSF to treat hydrocephalus.
• D. To inject contrast for imaging

Answer: (A)

The main idea here is that a lumbar puncture is performed to obtain cerebrospinal fluid for analysis to diagnose meningitis and other CNS conditions. By sampling CSF, clinicians can check cell count, glucose, protein, opening pressure, and perform Gram stain, cultures, and other tests to determine whether an infection is present and, if so, its likely cause (bacterial, viral, fungal, TB), which directly guides treatment.

Other potential uses of the procedure exist, such as relieving excess CSF pressure or delivering medications or contrast for imaging, but those are not the primary purpose in most cases. Measuring brain electrical activity is done with EEG, not lumbar puncture.