The leakage of cerebrospinal fluid (CSF, more commonly known as spinal fluid) occurs when there is an abnormal connection between the CSF-containing space around the brain and the paranasal sinuses. For a CSF leak to occur there has been a breakdown in the barrier that separates these two spaces. Causes of CSF leak include trauma and both brain and sinus surgery. In some patients, the CSF leak occurs spontaneously; that is, the leakage of spinal fluid starts without an easily identifiable cause.
Because untreated CSF leaks can lead to meningitis and brain infection, repair of CSF leaks is recommended. In the past, this required open brain surgery (i.e., craniotomy) for repair, but today, almost all CSF leaks can be closed by working through the nose and sinuses with endoscopic instruments (i.e., no external incisions).