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Cerebral Salt-Wasting Syndrome

Author: Sudha Garimella-Krovi, MBBS; Chief Editor: Stephen Kemp, MD, PhD more...

Updated: Jun 21, 2012

Background

First described by Peters et al in 1950, cerebral salt-wasting syndrome is defined by the development ofextracellular volume depletion due to a renal sodium transport abnormality in patients with intracranial disease and

normal adrenal and thyroid function.[1] As such, it may be more appropriately termed renal salt wasting.Complications of cerebral salt-wasting syndrome include symptomatic hyponatremia and dehydration. (SeePathophysiology, Etiology, and Presentation.)

Differentiation of this disorder from the syndrome of inappropriate antidiuretic hormone secretion (SIADH), acommon cause of hyponatremia, can be difficult because both can present with hyponatremia and concentratedurine with natriuresis. However, distinguishing between the 2 disorders is important because treatment optionsdiffer. Failure to distinguish cerebral salt-wasting syndrome from SIADH in a patient with hyponatremia who hasbrain injury could lead to inappropriate therapy with fluid restriction. (See Presentation and Workup.)

Although the diagnosis of cerebral salt-wasting syndrome is thought to be controversial by some,[2] it should be

considered a discrete clinical entity and may be more common than perceived.[3] It should also be considered in

patients without cerebral disease.[2, 4] Possible mechanisms for cerebral salt-wasting syndrome are shown in thechart below.

Possible mechanisms for cerebral salt-w asting syndrome. The injured brain may release natriuretic proteins that act directly on the

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kidney. In addition, cerebral injury may increase sympathetic nervous system activity, elevating renal perfusion pressure and releasing

dopamine.

Prognosis

Cerebral salt-wasting syndrome usually develops in the first week following a brain insult. Its duration is usuallybrief (spontaneously resolves in 2-4 wk), although it can last for several months. Death and complication rates forthis syndrome are not available. (See Treatment and Medication.)

Pathophysiology

Cerebral salt-wasting syndrome, or renal salt wasting, may be more common than SIADH and may even occur in

the absence of cerebral disease.[2, 3, 5] Although the exact mechanism that underlies the development of cerebralsalt-wasting syndrome is unclear, it is known that the initiating defect in renal sodium transport leads toextracellular volume depletion and that a cascade of compensatory changes occurs.

Abnormalities in the proximal tubule result in excessive sodium losses, which lead to decreased effectivecirculating volume. This activates baroreceptors, which increase antidiuretic hormone (ADH) secretion. This resultsin water conservation and a return to an equilibrated state. In contrast, SIADH primarily occurs due to aninappropriate euvolemic rise in ADH secretion.

The relationship among serum urate, fractional excretion of urate, and hyponatremia in cerebral salt-wastingsyndrome is unclear. Fractional excretion of urate may remain elevated even after correction of hyponatremia inpatients with cerebral salt-wasting syndrome. This is distinct from SIADH, in which the fractional excretion of urate

returns to the reference range once the hyponatremia is corrected.[4] The physiologic basis for this in cerebral salt-wasting syndrome may be related to the receptor-mediated processing of sodium and urate in the proximal tubule,which may be defective in this syndrome. The physiologic basis for hypouricemia in SIADH remains unclear.

The abnormalities in proximal tubular transport may be secondary to a plasma natriuretic factor that reducesproximal and, possibly, distal sodium transport in cerebral salt-wasting syndrome. It may also inhibit the tubular

transport of urate, phosphate, and urea in addition to sodium.[6]

Etiology

Cerebral salt-wasting syndrome, or renal salt wasting, occurs in the setting of acute central nervous system (CNS)disease. Conditions leading to cerebral salt-wasting syndrome include the following:

Head injuryBrain tumorIntracranial surgeryStroke

Intracerebral hemorrhage[7]

Tuberculous meningitisCraniosynostosis repair

However, cerebral salt-wasting syndrome can also occur in the absence of cerebral disease.[5]

The exact mechanism underlying cerebral salt-wasting syndrome remains unclear. In the setting of cerebral injury,one hypothesis is that an exaggerated renal pressurenatriuresis response caused by increased activity of thesympathetic nervous system and dopamine release is responsible for urinary sodium loss.

Another hypothesis involves the release of natriuretic factors, possibly including brain natriuretic peptide (C-typenatriuretic peptide) or urodilatin by the injured brain. Kojima et al have described an animal model of cerebral salt-

wasting syndrome that may allow better clarification of the conditions etiology.[8]

Epidemiology

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Occurrence in the United States

Exact incidence data for this disorder are not available. Approximately 60% of children with brain injuries or tumorsdevelop hyponatremia during their hospital course. Some experts suggest that cerebral salt-wasting syndrome(renal salt wasting) is responsible for hyponatremia at least as often as SIADH is, particularly in neurosurgicalpatients. Other studies indicate that this syndrome explains the development of hyponatremia in no more than 6%

of patients with acute brain injuries.[9] The exact incidence of renal salt-wasting syndrome without cerebral diseaseis also unknown.

Age-related demographics

Cerebral salt-wasting syndrome can occur at any age. Published reports include patients aged 6 months to 65years.

Contributor Information and DisclosuresAuthorSudha Garimella-Krovi, MBBS Clinical Assistant Professor of Pediatrics, University of Buffalo, StateUniversity of New York School of Medicine and Biomedical Sciences

Sudha Garimella-Krovi, MBBS is a member of the following medical societies: American Society of PediatricNephrology

Disclosure: Nothing to disclose.

Coauthor(s)James E Springate, MD Professor of Pediatrics, University of Buffalo, State University of New York School ofMedicine and Biomedical Sciences; Attending Physician, Department of Pediatrics, Division of Nephrology,Women and Children's Hospital of Buffalo

James E Springate, MD is a member of the following medical societies: American Academy of Pediatrics,American Physiological Society, American Society of Pediatric Nephrology, International Pediatric TransplantAssociation, and Society for Pediatric Research

Disclosure: Nothing to disclose.

Chief EditorStephen Kemp, MD, PhD Professor, Department of Pediatrics, Section of Pediatric Endocrinology, Universityof Arkansas for Medical Sciences College of Medicine, Arkansas Children's Hospital

Stephen Kemp, MD, PhD is a member of the following medical societies: American Academy of Pediatrics,American Association of Clinical Endocrinologists, American Pediatric Society, Endocrine Society, Phi BetaKappa, Southern Medical Association, and Southern Society for Pediatric Research

Disclosure: Nothing to disclose.

Additional ContributorsErawati V Bawle, MD, FAAP, FACMG Division of Genetic and Metabolic Disorders, Children's Hospital ofMichigan; Professor (Clinician-Educator), Department of Pediatrics, Wayne State University School of Medicine

Erawati V Bawle, MD, FAAP, FACMG is a member of the following medical societies: American Academy ofPediatrics, American College of Medical Genetics, American Medical Association, and American Society ofHuman Genetics

Disclosure: Nothing to disclose.

Barry B Bercu, MD Professor, Departments of Pediatrics, Molecular Pharmacology and Physiology, Universityof South Florida College of Medicine, All Children's Hospital

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Barry B Bercu, MD is a member of the following medical societies: American Academy of Pediatrics, AmericanAssociation of Clinical Endocrinologists, American Federation for Clinical Research, American MedicalAssociation, American Pediatric Society, Association of Clinical Scientists, Endocrine Society, Florida MedicalAssociation, Lawson-Wilkins Pediatric Endocrine Society, Pituitary Society, Society for Pediatric Research,Society for the Study of Reproduction, and Southern Society for Pediatric Research

Disclosure: Nothing to disclose.

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College ofPharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

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