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In addition to the causes of gait disturbances in old age that were listed in the article I wish to mention another cause of gait disturbances that has hardly received any attention but is clinically highly relevant. Patients with mild chronic hyponatremia fall notably more frequently than patients with normal serum concentrations of sodium. Hyponatremia affects gait more strongly than a blood alcohol concentration of 0.6 g/L. Gait disturbances are reversible after the hyponatremia has been corrected (1). In older patients, hyponatremia is associated with fractures (2). Hyponatremia is twice as common in patients with fractures as in those admitted without fractures.

The cause of the gait disturbance is “hyponatremic encephalopathy,” which is probably the result of a decrease of important, functional, intracellular osmolytes in the brain, such as glutamate and glutamine, in the context of volume adaptation of the brain (3). Further, signs of a reversible decrease in peripheral nerve conduction velocity has been observed in hyponatremia.

According to a large study, 14.5% of patients have hyponatremia on admission to hospital (4). Often this is associated with certain medications. Often, patients develop hyponatremia while receiving treatment with hydrochlorothiazide (HCT), after taking medications that have a neurological effect (antidepressants), or while being treated with carbamazepine.

It is likely that the number of hospital admissions owing to falls could be reduced if we paid more attention to hyponatremia and reacted appropriately. Diagnostic and therapeutic algorithms are available for this purpose.

DOI: 10.3238/arztebl.2010.0709a

Prof. Dr. med. Johannes Hensen

Medizinische Klinik

Klinikum Hannover

Haltenhoffstr. 41

30167 Hannover, Germany

johannes.hensen@krh.eu

Conflict of Interest Statement
In recent years, the author has received honoraria from Otsuka and other companies for scientific studies, lectures, and advisory activities regarding antidiuretic hormone (ADH)-(vasopressin) receptor antagonists, which are used to treat hyponatremia in the syndrome of inappropriate secretion of antidiuretic hormone (SIADH).

1.
Renneboog B, Musch W, Vandemergel X, Manto MU, Decaux G: Mild chronic hyponatremia is associated with falls, unsteadiness, and attention deficits. Am J Med 2006; 119(1): 71.e1–8. MEDLINE
2.
Ayus JC, Moritz ML: Bone disease as a new complication of hyponatremia: moving beyond brain injury. Clin J Am Soc Nephrol 2010; 5(2): 167–8. MEDLINE
3.
Verbalis JG, Gullans SR: Hyponatremia causes large sustained reductions in brain content of multiple organic osmolytes in rats. Brain Res 1991; 567(2): 274–82. MEDLINE
4.
Waikar SS, Mount DB, Curhan GC: Mortality after hospitalization with mild, moderate, and severe hyponatremia. Am J Med 2009; 122(9): 857–65. MEDLINE
5.
Jahn K, Zwergal A, Schniepp R: Gait disturbances in old age—classification, diagnosis, and treatment from a neurological perspective [Gangstörungen im Alter – Klassifikation, Diagnostik und Therapie aus neurologischer Sicht]. Dtsch Arztebl Int 2010; 107(17): 306–16. VOLLTEXT
1.Renneboog B, Musch W, Vandemergel X, Manto MU, Decaux G: Mild chronic hyponatremia is associated with falls, unsteadiness, and attention deficits. Am J Med 2006; 119(1): 71.e1–8. MEDLINE
2.Ayus JC, Moritz ML: Bone disease as a new complication of hyponatremia: moving beyond brain injury. Clin J Am Soc Nephrol 2010; 5(2): 167–8. MEDLINE
3.Verbalis JG, Gullans SR: Hyponatremia causes large sustained reductions in brain content of multiple organic osmolytes in rats. Brain Res 1991; 567(2): 274–82. MEDLINE
4.Waikar SS, Mount DB, Curhan GC: Mortality after hospitalization with mild, moderate, and severe hyponatremia. Am J Med 2009; 122(9): 857–65. MEDLINE
5.Jahn K, Zwergal A, Schniepp R: Gait disturbances in old age—classification, diagnosis, and treatment from a neurological perspective [Gangstörungen im Alter – Klassifikation, Diagnostik und Therapie aus neurologischer Sicht]. Dtsch Arztebl Int 2010; 107(17): 306–16. VOLLTEXT