Neurological disorders in pregnancy
Eclampsia: Eclampsia complicates approximately 1/2,000 pregnancies in developed countries and, although uncommon, is one of the leading causes of maternal mortality. Eclampsia (likely due to secondary ischemia caused by cerebral vasospasm) is the occurrence of a seizure or coma in association with pre-eclampsia (characterized by hypertension - SBP >140 mmHg or DBP >90 mmHg requiring 2 such abnormal BP measurements recorded at least 6 hours apart in a woman known to be normotensive prior to pregnancy - and proteinuria - at least 1+ on dipstick testing in at least 2 random urine samples collected at least 6 hours apart). Eclampsia is characterized by the occurrence of 1 or more seizures during pregnancy, delivery or up to 23 days postpartum. By definition, ≥2 of the following features must also be present within 24 hours of the seizure: hypertension, proteinuria, thrombocytopenia, elevated serum AST levels. Other systemic derangements include: increased peripheral vascular resistance, increased left ventricular stroke work index, decreased central venous and pulmonary wedge pressure, coagulopathy, increased blood viscosity, decreased plasma volume, hemoconcentration, decreased renal function, hepatocellular damage, cerebral hemorrhage and/or edema. HELLP (hemolytic anemia, elevated liver enzymes, low platelet count) syndrome occurs in approximately 10% of pregnant women with pre-eclampsia or eclampsia. Laboratory investigations should include: CBC, 24-h protein/creatinine, serum electrolytes (including magnesium), liver function tests (LDH, AST), uric acid, serum glucose and urgent brain CT scan or MRI.
Unfortunately, it is extremely difficult to predict which women with pre-eclampsia will develop eclamptic seizures. Consequently, it is almost impossible to devise strategies for seizure prophylaxis in pre-eclamptic women, and the routine use of anticonvulsant prophylaxis in all women with pre-eclampsia is controversial. In women with eclampsia, delivery of the infant is the only way to restore health. If the patient is experiencing a seizure, i.v. diazepam is commonly used while for the prevention of recurrent eclamptic seizure magnesium sulfate has proven to be superior to any other anticonvulsant (e.g. phenytoin). The loading dose consists of 4g (=16 mmol of magnesium) of a 10% solution of magnesium sulfate i.v. (administered over 10 min ) followed by i.v. infusion (controlled infusion pump) 1 to 2 g/h of a 10% solution of magnesium sulfate for at least 24h after the last seizure. If seizure recurs, additional dose by i.v. injection of 2g (4g if body weight > 70kg). Contraindications to magnesium sulfate are heart block and history of myocardial ischemia. During its therapy, monitored for signs of hypermagnesemia (absent patellar reflex and respiratory rate ≤ 16 min) is essential. The first clinical warning of impending toxicity in the mother is usually loss of the patellar reflex, typically at serum magnesium levels between 3.5 and 5 mmol/L. Serum magnesium levels should be monitored particularly in women with renal disease (urinary output ‹ 100 ml/4h)(target level of magnesium should be between 2-4 mmol/L). The overall tolerability profile of magnesium sulfate is well established and maternal adverse effects with serum magnesium levels of 3.8 to 5.0 mmol/L consist of flushing, increased warmth, headaches, blurred vision, nausea, nystagmus, lethargy, hypothermia, urinary retention and faecal impaction. Overdose leads to cardiac arrest. Magnesium sulfate readily crosses the placenta, and neonatal hypermagnesemia can occur. Drug interactions should be considered e.g. with depolarizing/non-depolarizing neuromuscular blockers, CNS depressants (e.g. opioids, barbiturates, general anesthetics) and nifedipine. Hypertension should be controlled with labetolol or α-methyldopa. The outlook for full recovery from eclampsia is very good. Most women begin to improve within one to two days after delivery, and blood pressure returns to the normal pre-pregnancy range within the next 6-12 weeks. Essential differential diagnosis are cerebral tumors, CVT, drug overdoses, epilepsy, intracranial hemorrhage, stroke (ischemic or non-ischemic) and electrolyte imbalance.