Cerebral
salt-
wasting syndrome (CSWS) has been regarded as a misnomer of the syndrome of inappropriate secretion of
antidiuretic hormone (
SIADH). We take the position that CSWS does exist and might be more common than
SIADH. Differentiation between groups has been difficult because of overlapping signs, 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. Determination of serum
urate and fractional excretion rates of
urate can differentiate one group from the other. In both groups,
hyponatremia coexists with hypouricemia and increased fractional excretion of
urate. When the
hyponatremia is corrected by water restriction, hypouricemia and elevated FEurate correct in
SIADH but persist in CSWS. Persistent hypouricemia and elevated FEurate 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 had decreased blood volume, decreased central venous pressure, and inappropriately high urinary
sodium concentrations in the majority of them, suggesting that CSWS was more common than
SIADH in neurosurgical patients. Evidence for the presence of a plasma
natriuretic factor in CSWS is presented.