Hyponatraemia in a neurosurgical patient:: syndrome of inappropriate antidiuretic hormone secretion versus cerebral salt wasting

In summary, SIADH and CSW are two potential causes of hyponatraemia is patients with neurosurgical disorders. Distinguishing between these two disorders can be challenging, since there is considerable overlap in the clinical presentation. The primary distinction lies in the assessment of the EABV. SIADH is a volume expanded state due to ADH-mediated renal water retention. CSW is characterized by a contracted EABV resulting from renal salt wasting. Making an accurate diagnosis is important since the therapy of each condition is quite divergent. Vigorous salt replacement is indicated in patients with CSW while fluid restriction is the treatment of choice in patients with SIADH. Therapy indicated for one disorder but used in the other can potentially result in untoward clinical consequences.