Can you tell me what a lumbar puncture is and why is it done?
A spinal tap or lumbar puncture is a diagnostic test that allows examination of the fluid that surrounds the brain and spinal cord. This fluid is contained between the middle and inner layer of tissue covering the spinal cord and brain - the subarachnoid space.
A sample of the fluid, known as cerebrospinal fluid (CSF), is withdrawn for a range of tests that may reveal evidence of infection, injuries or bleeding in the brain or spinal cord. CSF is usually clear and colourless, but can appear cloudy in the presence of infection such as bacterial meningitis.
High levels of protein can indicate damage in the brain, spinal cord or one of the spinal root nerves next to the spinal cord.
Abnormal antibodies in the fluid can indicate the presence of multiple sclerosis, while low levels of glucose may suggest meningitis or cancer. Some conditions affecting the brain or spinal cord can increase the pressure of the fluid, so this is closely measured during the procedure. The test is usually carried out to confirm a diagnosis suggested by medical history and physical examination.
Is it a painful test and do you need to have a general anaesthetic when having it done?
Although not a particularly pleasant test, it is not generally done under general anaesthetic.
The procedure involves the insertion of a fine needle between two vertebrae in the lower spine below the level of the spinal cord, which does not extend the whole length of the bony, protective spinal column. The test takes approximately 15 minutes to complete and is usually performed on the ward at the patient's bedside. A local anaesthetic is used to numb the area before the needle is inserted. A couple of drops of the CSF is put into a test tube and sent to the laboratory for examination.
Are there usually adverse side effects afterwards?
Serious side effects are very rare after a lumbar puncture. However, it is estimated that one in 10 people who undergo a lumbar puncture develop a headache when they stand up after the test. This usually resolves within a few weeks.