Procedures · 01
Lumbar Puncture & CSF Analysis
Learning objectives
- 1.Explain how a lumbar puncture samples CSF
- 2.Interpret CSF findings for meningitis and hemorrhage
- 3.Understand when a spinal tap is indicated and its risks
A lumbar puncture (spinal tap) samples the cerebrospinal fluid (CSF) that bathes the brain and spinal cord. It is the definitive test for meningitis and encephalitis and a key tool for bleeding, inflammation, and some cancers that spread to the nervous system.
What the CSF tells you
| Finding | Suggests |
|---|---|
| High white cells, low glucose, high protein | Bacterial meningitis |
| High lymphocytes, near-normal glucose | Viral meningitis or some autoimmune causes |
| Red cells that do not clear | Subarachnoid hemorrhage |
| High protein with unusual cells | Inflammation, tumor, or demyelination |
The procedure is done with the patient curled to open the spaces between vertebrae, with a needle threaded into the fluid sac. It is safe when done carefully, but it is invasive and requires consent and attention to bleeding risk and pressure concerns.
Prerequisite & related chapters