Cerebral Magnesium Levels in Preeclampsia; A Phosphorus Magnetic Resonance Spectroscopy Study

Magnesium sulfate (MgSO4) is used as a prophylaxis for eclamptic seizures. The exact mechanism of action is not fully established. We used phosphorus magnetic resonance spectroscopy (31P-MRS) to investigate if cerebral magnesium (Mg2+) levels differ between women with preeclampsia, normal pregnant, and nonpregnant women.

This cross-sectional study comprised 28 women with preeclampsia, 30 women with normal pregnancies in corresponding gestational week (range: 23-41 weeks) and 11 nonpregnant healthy controls. All women underwent 31P-MRS from the parieto-occipital region of the brain and were interviewed about cerebral symptoms. Differences between groups were assessed by analysis of variance and Tukey's post-hoc test. Correlations between Mg2+ levels and specific neurological symptoms were estimated with Spearman's rank test.

Mean maternal cerebral Mg2+ levels were lower in women with preeclampsia (0.12 mM ± 0.02) compared to normal pregnant controls (0.14 mM ± 0.03) (P = 0.04). Nonpregnant and normal pregnant women did not differ in Mg2+ levels. Among women with preeclampsia, lower Mg2+ levels correlated with presence of visual disturbances (P = 0.04). Plasma levels of Mg2+ did not differ between preeclampsia and normal pregnancy.

Women with preeclampsia have reduced cerebral Mg2+ levels, which could explain the potent antiseizure prophylactic properties of MgSO4. Within the preeclampsia group, women with visual disturbances have lower levels of Mg2+ than those without such symptoms.