Epilepsy in women: the science of why it is special.

Epilepsy is a common neurological disorder that may be affected by reproductive hormones and may complicate reproductive health. Many women with epilepsy experience changes in seizure frequency and severity with changes in reproductive cycles, including at puberty, over the menstrual cycle, with pregnancy and at menopause. Ovarian steroids alter neuronal excitability at the membrane and in the genome. Altered protein synthesis as a consequence of changes in RNA mediated gene transcription is one mechanism for steroid mediated effects on excitability. These genomic effects are delayed and sustained. In contrast, membrane effects are immediate and short duration. These effects are mediated at both the GABA-A and NMDA receptors. Estrogen also dynamically alters synaptic connectivity. Estrogen enhances excitability and lowers the seizure threshold, whereas progesterone enhances inhibition and increases the seizure threshold. In experimental models of epilepsy, estrogen is proconvulsant and progesterone is anticonvulsant. The net effect of these steroid actions is to alter neuronal excitability over physiological cycles. Some epilepsy syndromes are expressed or worsened at puberty. One third to one half of women with epilepsy have catamenial seizure patterns, with seizures most likely to occur in the perimenstrual period and at ovulation. More research is needed to understand the effects of menopause on epilepsy. Antiepileptic drugs may exacerbate the risk of reproductive endocrine disorders in women with epilepsy. Fertility rates are lower for women with epilepsy. Women with epilepsy are more likely to have anovulatory menstrual cycles, abnormal pituitary LH release and altered ovarian steroid concentrations. Polycystic ovaries are detected more often in women with epilepsy, particularly those on valproate. Treatment of hormone sensitive seizures relies on standard AEDs. Small trials suggest that adjunctive progesterone therapy is sometimes helpful. The newer AEDs, gabapentin and lamotrigine may have some advantages for women with epilepsy. These drugs do not alter levels of steroid hormones and do not interfere with effectiveness of hormonal contraception. Experience in pregnancy is limited. The dynamic effects of hormones on seizure expression and of seizures on reproductive health complicate the management of epilepsy in women. Newer AEDs may offer advantages for women with epilepsy in the reproductive years.