Also known as a “spinal tap,” a lumbar puncture is used to give doctors the ability to extract and test the cerebrospinal fluid that surrounds and helps protect the spinal cord and brain. A sample of this fluid is obtained through the insertion of a needle between two vertebrae of the lower spine. Through an examination of the cerebrospinal fluid, physicians can detect and diagnosis cancers and other serious conditions involving the central nervous system. Additionally, during a lumbar puncture medications may be injected into the cerebrospinal fluid to aid in the treatment of cancers or other conditions, as may dyes that aid in diagnostic imaging.
There are other reasons why a lumbar puncture may be performed: by measuring the pressure of the cerebrospinal fluid, doctors can act to relieve pressure around the brain or spinal cord. The procedure can also help in detecting diseases such as multiple sclerosis, hemorrhages, and infections such as encephalitis, meningitis, and syphilis.
Performed on an outpatient basis, a patient will lie on their side or lean forward while sitting, as either position flexes the back and spine and makes it visualize the point of needle insertion. Often a local anesthesia will be used to numb the area, after which the thin and hollow needle is inserted into the spinal canal (the needle doesn’t come in contact with the spinal cord, however). Once fully inserted the physician measures spinal fluid pressure and a small amount of the fluid is withdrawn.
Once the cerebrospinal fluid is withdrawn and available for testing, a number of diseases, disorders and health conditions can be ascertained from the sample. For example, if the fluid appears cloudy, red, orange or brown, an infection may be present or there may be current or prior bleeding or an obstruction in the spinal cord. Additionally, an increased level of white blood cells or the presence of foreign organisms may indicate an infection or onset of a disease or illness. The detection of an elevated protein level may be a sign of diabetes, a tumor or a diagnosis of multiple sclerosis, Guillain-Barre syndrome or syphilis. And if glucose levels have risen or fallen, this may indicate high or low blood sugar or an infection.