During a lumbar puncture, a needle is inserted into the lower part of the spinal column to collect cerebrospinal fluid (CSF), or to administer medications.
Patients are asked to sit up or lie down on their side with chin tucked against their chest and legs curled in the fetal position.
The skin is cleansed and a sterile sheet is draped over the area. In some cases, a numbing medicine, such as lidocaine, is injected under the skin.
The cerebrospinal fluid (CSF) flows out of the needle and into a plastic container that is sent to a laboratory for a variety of tests.
Under experienced hands there is usually only mild pain. Occasionally, some people may feel numbness shooting down the leg. This may be due to irritation of a nerve root and when the needle is withdrawn.
Following the procedure, the patient is advised to remain lying down for a short time to prevent low-pressure headache. The entire procedure takes approximately 15-20 minutes.
Reference: The National Institute of Neurological Disorders and Stroke (NINDS)