AVP and Hyponatremia: Common neurological pathologies, including subarachnoid haemorrhage, cerebrovascular accidents, brain tumour and head trauma [5,6,7], result in hyponatremia secondary to the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) or to the cerebral salt wasting syndrome (CSW), which are a consequence of the release of ADH or natriuretic peptides, respectively, from the brain as a response to an injury.