Hyponatremia and risk of seizures: a retrospective cross-sectional study.

This retrospective cross-sectional study was carried out to study the association between different levels of hyponatremia and the occurrence of epileptic seizures in patients without a prior epilepsy diagnosis. We identified from the hospital database, 363 inpatients of a Swedish County hospital who between March 2003 and August 2006 were found to have serum sodium levels <125 mM. Medical records were reviewed and we identified 11 patients with seizures in conjunction with their hyponatremia. Seizures were the only neurologic manifestation of hyponatremia in patients with serum sodium levels >115 mM. Of 150 patients reviewed with serum sodium levels of 120-124 mM, one had a seizure. Using 120-124 mM as reference, odds ratios (95% confidence interval) for having seizures at serum sodium levels of 115-119 mM was 3.85 (0.40-37.53), 8.43 (0.859-82.85) at 110-114 mM, and 18.06 (1.96-166.86) at <110 mM.