Lumbar Puncture
In a lumbar puncture a needle is inserted into the space below the spinal cord and a sample of the cerebrospinal fluid is taken. This is the clear, watery fluid that surrounds the brain and spinal cord. People with MS often have abnormal numbers of white blood cells or antibodies in their fluid, but similar findings can occur in other diseases too.
Lumbar puncture is carried out under local anaesthetic and is not usually painful. However, it can be uncomfortable and involves lying flat for several hours afterwards. You may have to stay in hospital overnight, and may have a slight headache afterwards.