Lumbar puncture is especially helpful in the diagnosis of inflammatory diseases of the central nervous system; especially, infections, such as meningitis. Lumbar puncture can also provide clues to the diagnosis of stroke, spinal cord tumor, and cancer in the central nervous system.
A lumbar puncture is so-called because the needle goes into the lumbar portion of the back. Other names for a lumbar puncture (an LP) include spinal puncture, thecal puncture, and rachiocentesis.
A lumbar puncture can also be done for therapeutic purposes; namely, as a way of administering antibiotics, cancer drugs, or anesthetic agents into the spinal canal.
Spinal fluid is sometimes removed by lumbar puncture for the purpose of decreasing spinal fluid pressure in patients with uncommon conditions; such as, normal-pressure hydrocephalus and benign intracranial hypertension.
After a local anesthesia is injected into the small of the back (the lumbar area), a needle is inserted in between the nearby bony building blocks (vertebrae) into the spinal canal to make the lumbar puncture. The needle is usually placed between the 3rd and 4th lumbar vertebrae. Spinal fluid pressure can then be measured and cerebrospinal fluid (CSF) removed for testing.
The cerebrospinal fluid circulates around the brain and spinal cord (the central nervous system). This "water bath" acts as a support of buoyancy for the brain and spinal cord. The support of the cerebrospinal fluid helps to protect the brain from injury.
Spinal fluid obtained from the lumbar puncture can be used to diagnose many important diseases: such as, bleeding around the brain; increased pressure from hydrocephalus; inflammation of the brain, spinal cord, or the adjacent tissues (encephalitis, meningitis); tumors of brain or spinal cord, etc. Sometimes spinal fluid can indicate diseases of the immune system; such as, multiple sclerosis.
When spinal fluid is removed during a lumbar puncture, the risks include headache, brain herniation, bleeding, and infection. Each of these complications are uncommon with the exception of headache, which can appear from hours to up to a day after lumbar puncture.
Headaches occur less frequently when the patient remains lying flat one to three hours after the procedure. The benefits of the lumbar puncture depend on the exact situation but a lumbar puncture can usually provide lifesaving information.