The brain is fully encased inside a lining called dura. The brain and the dura are positioned partly above the nose and the sinuses that are separated from them by a thin bone. Any perforation in the bone and the dura can leak the CSF(cerebrospinal fluid) straight into the nasal or the throat cavities.
CSF leakage can occur due to a head injury, complication from sinus or brain injury or due to tumour removal from inside a sinus. The CSF leak becomes visible when clear fluid starts draining from the nose (usually from one nostril) or into the back of the throat (tastes salty).
