Cerebral salt-wasting syndrome: Does it exist?

Cerebral salt-wasting syndrome (CSWS) has been regarded as a misnomer of th e syndrome of inappropriate secretion of antidiuretic hormone (SIADH). We t ake the position that CSWS does exist and might be more common than SIADH, Differentiation between groups has been difficult because of overlapping si gns, symptoms, and associated diseases. Euvolemia in SIADH and hypovolemia in CSWS may be the only contrasting variables. However, clinical assessment of extracellular volume is accurate in about 50% of these patients. Determ ination of serum urate and fractional excretion rates of urate can differen tiate one group from the other. In both groups, hyponatremia coexists with hypouricemia and increased fractional excretion of urate, When the hyponatr emia is corrected by water restriction, hypouricemia and elevated FEurate c orrect in SIADH but persist in CSWS. Persistent hypouricemia and elevated F Eurate were commonly noted with pulmonary and/or intracranial diseases. The absence of intracranial diseases in some patients suggests that renal salt wasting might be a more appropriate term than CSWS, A review of renal/CSWS reveals three studies involving hyponatremic neurosurgical patients who ha d decreased blood volume, decreased central venous pressure, and inappropri ately high urinary sodium concentrations in the majority of them, suggestin g that CSWS was more common than SIADH in neurosurgical patients. Evidence for the presence of a plasma natriuretic factor in CSWS is presented.