What procedure inserts a needle into the spine to collect cerebrospinal fluid?

The procedure that inserts a needle into the spine to collect cerebrospinal fluid is a lumbar puncture.

Also called a spinal tap, it is performed in the lower back rather than through the spinal cord itself. A thin, hollow needle passes between lumbar vertebrae—commonly between L3-L4 or L4-L5—into the space containing cerebrospinal fluid, or CSF. The fluid surrounds and cushions the brain and spinal cord.

Doctors may analyze CSF for evidence of meningitis, encephalitis, bleeding, multiple sclerosis, or other neurological conditions. Lumbar puncture can also deliver medicines, including certain anesthetics, antibiotics, or cancer treatments. The procedure was introduced clinically by German physician Heinrich Quincke in 1891.

A lumbar puncture is different from an epidural injection, which places medication outside the dura surrounding the spinal canal, usually for pain relief or anesthesia. A myelogram is an imaging examination that uses contrast material to visualize structures around the spinal cord.