A cerebrospinal fluid (CSF) leak occurs when CSF is abnormally leaking from the brain's subarachnoid space. This condition occurs when a rupture affects the arachnoid membrane, usually after surgery, trauma or a spinal tap. Approximately 1 percent of patients will experience a CSF leak associated with a herniated disc (also called a ruptured disc), according to the Steadman Clinic. This can happen if a hole develops when the surgeon removes or looks for the herniated disc. The signs and symptoms of a CSF leak will vary.