A procedure for removing CEREBROSPINAL FLUID (CSF) from the spinal canal in the LUMBAR region in order: (1) to diagnose disease of the nervous system; (2) to introduce medication – spinal anaesthetics or drugs. A hollow needle is inserted into the lower section of the SPINAL CORD (see diagram) and the cerebrospinal fluid withdrawn. Examination of the cerebrospinal fluid helps in the diagnosis and investigation of disorders of the brain and spinal cord – for example, MENINGITIS and SUBARACHNOID HAEMORRHAGE.