Hyponatremia in Neurosurgical Patients

Hyponatremia is a frequent occurrence in patients with neurosurgical disorders. Acute onset hyponatremia is particularly common in patients who have any type of cerebral insult, including traumatic brain injury, subarachnoid hemorrhage, and brain tumors. Furthermore, it is a common complication of intracranial procedures. Acute hyponatremia creates an osmotic gradient between the brain and the plasma, which promotes the movement of water from the plasma into brain cells, causing cerebral edema and neurological compromise. It is therefore far more likely to be symptomatic, and to have adverse outcomes, than chronic hyponatremia. Uncorrected acute hyponatremia with consequent cerebral edema may manifest through impaired consciousness level, seizures, elevated intracranial pressure, and, potentially, death due to cerebral herniation. The majority of cases of hyponatremia due to neurosurgical pathology are caused by the syndrome of inappropriate antidiuresis, but acute glucocorticoid insufficiency is increasingly being recognized as an important contributing factor. In this chapter, we summarize the existing literature on the clinical features and differential diagnosis of hyponatremia in the neurosurgical patient, and briefly discuss the management options.