Hyponatraemia is the most frequent electrolyte disorder of hospitalised patients. Cerebral salt-wasting syndrome
(CSWS) is rare, but serious cause of hyponatraemia of patients with diseases of the central nervous system (CNS). An excessive
creation of natriuretic peptides, especially BNP, is considered its cause. Its consequence is excessive renal natrium
loss accompanied by the decrease in extracellular fluid volume (ECFV). In the differential diagnostics, it is inevitable
to distinguish CSWS from the syndrome of inappropriate antidiuretic hormone secretion (SIADH), which has some
similar laboratory findings, but it differs in a normal or increased ECFV. This difference requires a therapeutical approach.
A decreased intake of liquids indicated at SLADH might be inappropriate in patients with CSWS. On the contrary,
the administration of isotonic solutions might deepen hyponatraemia if SIADH is its cause.