CSF obtained by lumbar puncture can be used for diagnostic purposes.

• A. To diagnose conditions
• B. To measure brain activity
• C. To deliver medication into brain
• D. To assess blood flow noninvasively

Answer: (A)

Analyzing CSF from a lumbar puncture is a diagnostic tool that provides direct clues about diseases affecting the central nervous system. By measuring opening pressure and examining the CSF’s contents—cell count and differential, protein, glucose—and running tests such as Gram stain, bacterial culture, viral PCR, and cytology, clinicians can identify infections, inflammatory or autoimmune processes, bleeding into the CNS, and malignant disease. For example, bacterial meningitis often shows high opening pressure, neutrophil-predominant pleocytosis, low glucose, and high protein, while viral meningitis tends toward lymphocytes with relatively normal glucose. CSF analysis can also detect malignant cells in carcinomatous meningitis or reveal oligoclonal bands in multiple sclerosis. In contrast, measuring brain activity is done with EEG, delivering medications into the CNS is a therapeutic route rather than a diagnostic use, and noninvasive assessment of blood flow is achieved with imaging studies—not CSF analysis. So, lumbar puncture CSF is primarily used to diagnose conditions.