Effect of magnesium sulfate on electroencephalographic findings in preeclampsia-eclampsia.

Electroencephalograms (EEGs) were recorded in 36 eclamptic, 14 preeclamptic, and 13 normotensive control patients. In the eclamptic group, EEGs were recorded while patients were receiving intravenous magnesium sulfate (MgSO4) with serum magnesium (Mg) levels of 4.5 to 11 mg/dL, and recorded again after MgSO4 was discontinued (serum Mg levels 1.8 to 2.5 mg/dL). In preeclamptic patients, EEGs were recorded before starting MgSO4, during administration of the loading dose (serum Mg levels 6 to 10 mg/dL), and eight hours through the maintenance dose (serum Mg levels 3.6 to 6.2 mg/dL). Twenty-seven (75%) eclamptic patients had abnormal EEGs, four patients showed paroxysmal spike activity, and the others showed focal or diffuse slowing (delta waves). Seven (50%) preeclamptic women had abnormal EEGs (all had generalized slowing). In preeclamptic-eclamptic patients who had serial EEG recordings, the gross EEG findings obtained during MgSO4 infusion and in the absence of MgSO4 were similar. In addition, the abnormal EEG findings were frequent despite the serum Mg levels considered therapeutic in the clinical management of these patients. Two eclamptic patients had seizure activity at serum Mg levels of 9.6 and 11 mg/dL. These findings suggested that abnormal EEGs are frequent in preeclamptic-eclamptic patients. Abnormal EEG findings in such patients are not altered by serum Mg levels achieved in the clinical management of these patients.