CSF is an abbreviation for cerebral spinal fluid. This procedure is similar to a joint tap, but instead of going into the joint with a needle you are going into the central nervous system with a needle to obtain fluid for analysis. It requires general anesthesia to perform the procedure because it is imperative that the patient not move at all because it is an extremely delicate procedure. Once the fluid is obtained it can be sent off for analysis to differentiate between inflammation, infection and cancer.