Electrolyte Blood Press.  2009 Dec;7(2):51-57. 10.5049/EBP.2009.7.2.51.

Hyponatremia in Patients with Neurologic Disorders

• Kim DK
• Joo KW

• KMID: 2052319
• DOI: http://doi.org/10.5049/EBP.2009.7.2.51

Abstract

The kidney and the brain play a major role in maintaining normal homeostasis of the extracellular fluid by neuroendocrine regulation of sodium and water balance. Therefore, disturbances of sodium balance are common in patients with central nervous system (CNS) disorders and clinicians should focus not only on the CNS lesion, but also on the potentially deleterious complications. Hyponatremia is the most common and important electrolyte disorder affecting patients with critical neurologic diseases. In these patients, the maladaptation to hyponatremia by impaired osmoregulation in pathologic lesions of brain may cause more aggressive cerebral edema and increased intracranial pressure due to hypoosmolality induced by hyponatremia. Furthermore, hyponatremia accompanied by CNS disorders has shown to increase delayed cerebral ischemia and mortality rates. Two main pathophysiologies of hyponatremia, excluding iatrogenic causes, are inappropriate secretion of antidiuretic hormone (SIADH) and cerebral salt wasting (CSW) syndrome. Differential diagnosis between these two entities can be difficult due to considerable overlap in the laboratory findings and clinical situations. SIADH is in a volume expanded status due to inappropriately secreted arginine vasopressin (AVP) and requires water restriction. However, CSW syndrome is characterized by renal sodium wasting mainly due to increased natriuretic peptides resulting in volume depletion and follows appropriate secretion of AVP. Therefore, maintenance of volume status and sodium replacement is the mainstay of treatment in CSW syndrome. In this review, we aimed to describe the regulation of sodium and water balance, and pathophysiology, diagnosis and treatment of hyponatremia in neurologic patients, especially focusing on SIADH and CSW syndrome.

Keyword

hyponatremia; inappropriate ADH syndrome; cerebral salt wasting syndrome; nervous system diseases

MeSH Terms

Arginine Vasopressin
Brain
Brain Edema
Brain Ischemia
Central Nervous System
Diagnosis, Differential
Extracellular Fluid
Homeostasis
Humans
Hyponatremia
Inappropriate ADH Syndrome
Intracranial Pressure
Kidney
Natriuretic Peptides
Nervous System Diseases
Sodium
Water-Electrolyte Balance
Arginine Vasopressin
Natriuretic Peptides
Sodium
Water-Electrolyte Balance

Figure

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  Fig. 1 Role of arginine vasopressin in the regulation of water balance. AVP, arginine vasopressin; SON, supraoptic nucleus; PVN, paraventricular nucleus; V2R, V2 receptor; cAMP, cyclic adenosine monophosphate; AQP2, aquaporin 2.

• 

  Fig. 2 Pathophysiology of cerebral salt wasting syndrome. BNP, brain natriuretic peptide; RAS, rennin angiotensin system; AVP, Arginine vasopressin; GFR, glomerular filtration rate; IMCT, inner medullary collecting tubule.

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