A lumbar puncture is a medical procedure in which a sample of cerebrospinal fluid (CSF) is collected for analysis via a needle inserted into the lower portion of the spine. While it is most commonly performed in order to test for bacterial meningitis, it may also be employed to determine other conditions such as a brain hemorrhage, multiple sclerosis or Guillain-Barre syndrome. This is approximately a 30-minute procedure during which the patient lies on their side in a fetal position or sits leaning forward so that there is as much space between the vertebral bones in the back as possible. A topical anesthetic is often first applied to numb the skin prior to an anesthetic medication being injected into the tissues below. The physician then inserts the spinal needle between two lumbar vertebrae and collects the CSF material over the course of just a few minutes. Many patients do not experience much pain during the procedure, but they do need to remain on their back for a period of hours afterward, and some may experience a headache and/or backache once it is complete.