Find information on medical topics, symptoms, drugs, procedures, news and more, written for the health care professional.

Lumbar puncture.

Lumbar puncture.
Lumbar puncture.

For the procedure, the patient is typically in the left lateral decubitus position. A lumbar puncture needle with stylet is inserted into the L3-to L4 or L4-to-L5 interspace (the L4 spinous process is typically on a line between the posterior-superior iliac crests); the needle is aimed rostrally toward the patient’s umbilicus and always kept parallel to the floor. Entrance into the subarachnoid space is often accompanied by a discernible pop; the stylet is withdrawn to allow CSF to flow out.