Via The Bottom Line:
Cerebral salt wasting is associated with hypovolemic hyponatremia in patients with intracranial disease, such as subarachnoid hemorrhage, traumatic brain injury, craniotomy, encephalitis, and meningitis. SIADH is a cause of euvolemic hyponatremia due to the excess secretion of vasopressin that may be attributed to malignancy, various CNS or pulmonary disorders or drugs, such as chlorpropamide and carbamazepine.
The treatments differ completely but the distinction between the two can be very difficult. Both conditions have CNS disease in common and are biochemically similar. The diagnosis my hinge on volume assessment and response to treatment.