[Hyponatremia, cause of reversible dementia in the elderly].

There are several states of reversible dementias. Among these, electrolyte imbalance--especially hyponatremia--can determine transitory modification of cognitive functions. The purpose of this study is the evaluation of the relationship between cognitive disorders and serum sodium concentrations in the elderly. In a sample of 70 elderly people, the Authors reported a prevalence of hyponatremia in 28 patients (40%); only 4 (5.7% of total population) had impaired cognitive functions or mood disturbances. In the symptomatic patients hyponatremia was severe and had a fast onset; the symptoms disappeared by means a proper and ready treatment. This observation stresses out the importance of routine serum sodium determination in the elderly in coincidence with the sudden onset of a pattern of dementia.