Hyponatraemia in children with acute CNS disease: SIADH or cerebral salt wasting?

Hyponatraemia in patients with an acute central nervous system disease can be caused by two different mechanisms: (1) excretion of free water, i.e. th e syndrome of inappropriate secretion of antidiuretic hormone (SIADH) and ( 2) excessive sodium excretion, i.e., the cerebral salt wasting syndrome (CS W). Although the concept of CSW is well known in adult medicine, it is stil l not established in child neurology. We conducted a retrospective analysis of electrolyte disturbances in 195 children with various acute CNS disease s. In 20 children (10.3%) hyponatraemia with plasma sodium below 130 mmol/l was identified. On the basis of clinical and laboratory data 7 of these 20 children were diagnosed as having SIADH, and the other 9 children, as havi ng CSW. Our data suggest that hyponatraemia attributable to CSW is at least as frequent in children as SIADH. Because of their different pathophysiolo gical mechanisms, which require diametrically opposed therapeutic regimens, early differential diagnosis is mandatory if the correct treatment is to b e given.