DefinitionA CSF leak is an escape of the fluid that surrounds the brain and spinal cord.Alternative NamesIntracranial hypotensionCauses, incidence, and risk factorsThe dura is the membrane that surrounds the brain and spinal cord and contains the cerebrospinal fluid (CSF). CSF can leak from any hole or tear in the dura.Causes of a tear in the dura include:Certain head, brain, or spinal surgeriesHead injuryPlacement of tubes for epidural anesthesia or pain medicationsSpinal tap (lumbar puncture)Sometimes there is no cause.SymptomsSymptoms may include:A headache that is worse when you sit up and improves when you lay downDrainage from the ear (rarely)Runny noseSigns and testsDiagnosis is usually based on your history of injury, surgery, or lumbar puncture.Tests may include:Injection of a rad