HUMAN CEREBRAL OSMOLYTES DURING CHRONIC HYPONATREMIA - A PROTON MAGNETIC-RESONANCE SPECTROSCOPY STUDY

The pathogenesis of morbidity associated with hyponatremia is postulat ed to be determined by the state of intracellular cerebral osmolytes. Previously inaccessible, these metabolites can now be quantitated by p roton magnetic resonance spectroscopy. An in vivo quantitative assay o f osmolytes was performed in 12 chronic hyponatremic patients (mean se rum sodium 120 meq/liter) and 10 normal controls. Short echo time prot on magnetic resonance spectroscopy of occipital gray and parietal whit e matter locations revealed dramatic reduction in the concentrations o f several metabolites. In gray matter, myo-inositol was most profoundl y reduced at 49% of control value. Choline containing compounds were r educed 36%, creatine/phosphocreatine 19%, and N-acetylaspartate 11% fr om controls. Similar changes were found in white matter. Recovery of o smolyte concentrations was demonstrated in four patients studied 8-14 wk later. These results are consistent with a reversible osmolyte redu ction under hypoosmolar stress in the intact human brain and offer nov el suggestions for treatment and monitoring of this common clinical ev ent.