Abstract
Hydrocephalus is the pathological accumulation of cerebrospinal fluid within the ventricles of the brain. Hydrocephalus may be broadly divided into three categories: congenital, acquired, or other. Hyponatremia, serum sodium level <135 meq/ml, may be caused by dilution (e.g. syndrome of inappropriate antidiuretic hormone (SIADH)), depletion (e.g. cerebral salt wasting (CSW)), or delusion (e.g. psychogenic water intake) etiologies. This review discusses “hydrocephalus-associated hyponatremia” as a clinical entity, distinct from SIADH and CSW.Some experts believe that in hydrocephalus patients, increased pressure on the hypothalamus leads to the release of antidiuretic hormone (ADH), which in turn causes hyponatremia. The true etiology of hyponatremia is critical to diagnose, as it will determine the treatment. So while both SIADH and CSW may result in hyponatremia, the former is treated with fluid restriction, while the latter requires fluid repletion; treating SIADH as CSW, and vice versa, will exacerbate the hyponatremia.The etiology and severity of hyponatremia will determine the management. For hydrocephalus-associated hyponatremia, treating the underlying problem (i.e. hydrocephalus) is the mainstay of therapy. Theoretically, treatment of hydrocephalus-related hyponatremia with CSF-diversion procedures should relieve the pressure on the hypothalamus, mitigating ADH production, which in turn will decrease sodium excretion and ameliorate the hyponatremia.
Highlights
BackgroundHydrocephalus, hyponatremia, or a combination of these is frequently encountered in neurosurgical patients
Several case studies have shown that normal pressure hydrocephalus (NPH) induced the syndrome of inappropriate antidiuretic hormone (SIADH) release, suggesting a possible mechanical pressure related to ADH release as well [3,4,5]
Several journal articles have reported hydrocephalus-associated hyponatremia and several different theories have been proposed for this mechanism
Summary
Hydrocephalus, hyponatremia, or a combination of these is frequently encountered in neurosurgical patients. In a case report by Yoshino et al, a 79-year-old female was diagnosed with idiopathic NPH with hyponatremia caused by SIADH [3] When this patient was experiencing hyponatremia, high levels of ADH were seen even though the plasma osmolality was low. In a case report by Kumar et al, a 70-year-old male had hyponatremia and low serum osmolality [4] This patient had a brain CT, which showed hydrocephalus. It has been theorized that hydrocephalus, through the expansion of the third ventricle, may be applying mechanical pressure to the supraoptic and paraventricular nuclei of the hypothalamus [5] These nuclei are responsible for the production of ADH and it is believed that the mechanical pressure causes an uncontrolled release of the hormone causing serum hypoosmolality and serum hyponatremia. Having hyponatremia complicates hydrocephalus leading to poorer outcomes and increased complications
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