Basic technique of a lumbar puncture procedure
- Obtain computed tomography/magnetic resonance imaging (CT/MRI) brain indicated for patients with papilledema, altered mental status, focal neurologic deficit, new-onset seizure, or immunocompromised state.
- Ensure that platelet count is >50,000, and international normalized ratio is <1.5.
- Place patient in lateral decubitus position, with knees and neck flexed.
- Ensure patient’s back is as close to edge of bed as possible.
- Palpate top of iliac crest and then place thumb of same hand in the interspace forming a vertical line with the top of the iliac crest.
- The identified location indicates the L3-L4 space. The needle can be placed into the L3-L4, L4-L5, or L5-S1 interspaces.
- Avoid L2-L3 interspace and higher since the conus medullaris terminates at L1-L2.
- Insert needle, with the bevel parallel to longitudinal fibers of the supraspinous ligament.
- Advance needle, and a “pop” should be felt, indicating the piercing of the needle through the supraspinous ligament. Advance needle into the subarachnoid space.