Mark S. Yerby

Clinical Care of Pregnant Women with Epilepsy: Neural Tube Defects and Folic Acid Supplementation

Summary:  Women with epilepsy (WWE) have a risk of bearing children with congenital malformations that is approximately twice that of the general population. Most antiepileptic drugs (AEDs) have been associated with such risk. Valproate and carbamazepine have been associated specifically with the development of neural tube defects (NTDs), especially spina bifida. Other factors may contribute to the risk, including concomitant diseases such as diabetes mellitus, occupational exposure to teratogens, excessive prepregnancy weight, and various nutrient deficiencies. In the general population, maternal folate deficiency, in particular, has been linked with the development of NTDs, and periconceptional folate supplementation with a reduction of risk. It is unclear whether folate supplementation has a comparable protective effect for WWE. Data concerning the risk for congenital malformations associated with the newer AEDs (gabapentin, felbamate, lamotrigine, levetiracetam, oxcarbazepine, tiagabine, topiramate, and zonisamide) are still limited. Several pregnancy registries for women taking AEDs have been established. Comprehensive postmarketing surveillance, regionally or nationally, might be the ideal method of monitoring medication safety, but government support for such an undertaking has for the most part been lacking. Despite uncertainty about the efficacy of periconceptional folate supplementation in WWE, these women should receive such supplementation at dosage levels recommended for the general population of women of childbearing age. Seizure control must not be neglected in a pregnant woman with epilepsy since seizures are associated with harm to the fetus as well as the mother. Risk may be minimized by using a single AED at the lowest effective dosage.

Problems and Management of the Pregnant Woman with Epilepsy

Summary: Pregnancies occurring in women who are epileptic are considered to be high risk. These women are at increased risk of seizures during pregnancy, labor, and delivery and of pregnancy complications and adverse pregnancy outcomes. Pregnancy alters the pharmacokinetics of anticonvulsant drugs, the levels of which decline as pregnancy advances. Not all drugs are altered in a similar manner, however. The rate of congenital malformations in infants of epileptic mothers is 2.4 times higher than in the general population. Malformations occur with all of the commonly used anticonvulsant drugs. The possible mechanisms of teratogenicity include folic acid antagonism, fetal tissue binding, and toxic effects of metabolic intermediates. Therapy with more than one drug increases the risk of congenital malformations. A unique hemorrhagic phenomenon in the infants of epileptic mothers has been reported and appears to be the result of a deficiency of vitamin K‐dependent clotting factors. When taken by a pregnant woman, all antiepileptic drugs except valproic acid manifest themselves in breast milk, but only if the infant exhibits evidence of sedation should breastfeeding be discontinued. The dilemma for the physician treating the pregnant epileptic woman is to protect the mother from seizures and the fetus from unnecessary exposure to anticonvulsant medications.

Effects of Pregnancy on Antiepileptic Drug Utilization

Summary: Pregnancy is associated with characteristic changes in the disposition of antiepileptic drugs; recent findings on this aspect of drug utilization are presented. In one study involving 48 pregnancies, the mean level—dose ratio of phenytoin decreased by 34%. In another study of 111 patients, phenytoin clearance increased gradually over the first 32 weeks of pregnancy and reached twice the preconception value. In two studies with phenobarbital, levels tended to decrease, although this effect was less pronounced than for phenytoin. Similarly for primidone, pregnancy had little effect on steady‐state levels; however, levels of phenobarbital formed from primidone exhibited large decreases during pregnancy followed by increases after delivery. This effect was quite consistent. Carbamazepine clearance tended to increase to a relatively small extent. Limited data indicate that valproate levels decrease by 30 to 40% during pregnancy. The mechanisms responsible for these effects have not been elucidated and possibly include decreased bioavailability or compliance, increased metabolic clearance, or decreased plasma protein binding. Since the patient at risk of an increase in seizure frequency cannot be identified prior to conception, therapeutic monitoring is imperative during and after pregnancy.

Serum prolactins in the diagnosis of epilepsy Sensitivity, specificity, and predictive value

Serum prolactin levels rise after generalized tonic-clonic and partial complex seizures, but not after pseudoepileptic seizures. The criteria for a significant elevation in serum prolactin vary with individual investigators. The prevalence of pseudoseizures in the population studied determines the predictive value of serum prolactin determinations. In populations where most patients have epilepsy, a rise in serum prolactin is highly predictive for true epilepsy, but no increase in serum prolactin is not predictive for pseudoseizures.

Male infertility: possible association with valproate exposure.

Summary: Purpose: To describe a potential association between male infertility and valproate (VPA) exposure. VPA has been implicated in the development of polycystic ovarian disease and subsequent menstrual and infertility problems in women with epilepsy. Infertility has been well described in population‐based studies of persons with epilepsy. The low marital rates for men with epilepsy have previously been thought to play a major contributing role.

Risks of Pregnancy in Women with Epilepsy

Summary: Pregnant women with epilepsy are at increased risk of seizures and complications. An increase in seizure frequency is seen in 25–30% of pregnant women with epilepsy; the offspring of mothers who experienced seizures during pregnancy are at a 2.5 times higher risk for seizures later in life. One of the main reasons for the increase in seizures during pregnancy is a decline in plasma concentrations of antiepileptic drug (AED) that occurs as pregnancy progresses, largely as a result of marked alterations in plasma protein binding. It is well known that epilepsy represents a risk for a variety of adverse pregnancy outcomes or malformations, especially in polytherapy. The adverse outcomes range from dysmorphic features to hemorrhagic disorders resulting from a deficiency of vitamin K‐dependent clotting factors or to spina bifida. Folic acid supplements appear to reduce the risk of spina bifida. A strong genetic link seems to exist for many of the malformations that occur, and more research is required in this field. In the meantime, there are interventions that clinicians can already make to reduce the risk of adverse outcomes, such as seizure control without toxicity, monotherapy, and preconceptual use of vitamins with folate.

Valproic acid disposition and protein binding in pregnancy.

Summary: Nine epileptic women were followed prospectively through pregnancy on a monthly basis. At each visit, total and free serum valproic acid levels and albumin levels were obtained. Assays were done by gas-liquid chromatography, and free drug was separated by ultrafiltration. Despite an upward dose adjustment in four patients, total valproic acid levels declined as pregnancy proceeded, but free levels did not. Plasma free fractions and clearances increased, but intrinsic clearances, which were adjusted for changes in body weight, remained unchanged.

Use of unbound drug concentrations to determine neonatal anticonvulsant exposure

Unbound and total concentrations of several anticonvulsant drugs were measured by liquid chromatography in maternal and neonatal cord serum collected at birth from 16 women being treated for epilepsy and their newborns. Maternal and neonatal unbound drug concentrations agreed closely for phenobarbital (n = 6), phenytoin (n = 7), carbamazepine (n = 8), and its epoxide metabolite. Mean maternal total drug concentrations were higher than neonatal concentrations in the cases of phenobarbital, carbamazepine, its epoxide and diol metabolites. The differences were due to greater protein binding in maternal serum. Measurement of total anticonvulsant concentrations in newborns may be misleading, because of altered protein binding in the neonate. For the medications tested, neonatal and maternal exposures to unbound drug appear to be equivalent.

Case Reports of Women with Epilepsy

Women with epilepsy are faced with many unique issues regarding their reproductive health. Pregnancies in women with epilepsy are considered high risk because of the increased risk for seizures, maternal complications, and adverse outcomes in the newborn. Infants of women with epilepsy have a twoto threefold increase in the rate of fetal malformations. Investigators have hypothesized that the increased risks are secondary to genetic predisposition, exposure of the fetus to seizures, and in utero exposure to antiepileptic drugs (AEDs). However, the relative contribution of each factor is undetermined. Two similar cases of women with epilepsy involving pregnancy and the risk of neural tube defects (NTDs) are presented. Although the cases are similar, they illustrate the diverse challenges faced in the care of women with epilepsy and their unborn children.

Complex Partial Seizures Associated with a Temporomandibular Joint Defect

Summary: A case of a 32‐year‐old man is reported with complex partial seizures secondary to a right inferior temporal epileptic focus immediately overlying an abnormality of the temporomandibular joint, with a defect in the middle temporal fossa that allowed the mandibular condyle to contuse the temporal lobe.