Introduction

Pregnancy often modifies the clinical expression of neurological disease. It also introduces concerns regarding the safety of treatment of the mother on the developing fetus. Management of problems of the central and peripheral nervous system (whether major or minor), therefore present the treating clinician with particular challenges. This chapter will review some of the more important neurological diseases modified by, or affecting, pregnancy and some entities exclusively seen in pregnancy. A comprehensive review is beyond the scope of this chapter. The interested reader can consult a text on this subject (see references).

Sex differences in regional brain structure and Function

Several mammalian and avian species have significant gender differences in brain morphology and connectivity, although the study of humans shows more subtle gender differences. Principal among them, are the findings on neuroimaging of the relatively larger callosal isthmus in females, and the decreased lateralization of brain activation in females measured by fMRI during phonological processing of particular tasks (Shaywitz et al., 1995; Witelson, 1991). Studies have only begun to appreciate the effects of sex and age on the differences of brain structure, and future studies with functional imaging may reveal other differences.

The effect of ovarian hormones on the nervous System

During menstruation and pregnancy, the nervous system is exposed to different absolute and relative levels of estrogen and progesterone. In the brain, estrogen may have both trophic and transmitter roles with receptors being present in the CA 1 and CA 3 regions of the hippocampus, locus ceruleus, raphe nuclei, central grey matter and cingulate gyrus, but even more so in the preoptic region. Estrogen can induce new NMDA-mediated synapse formation and dendritic spine formation particularly in the limbic system, magnified by the presence of progesterone (McEwen et al., 1997). Estrogen also induces choline acetyl transferase in the basal forebrain cholinergic regions and their secondary projections (Luine, 1985). Progesterone often appears to have an opposite effect on neuronal systems.

These hormones may influence the clinical expression of neurological problems such as migraine, epilepsy, brain tumours, autoimmune diseases and neuromuscular diseases. Accurately predicting how a particular disease will be clinically modified by hormones, or basing therapy on these presumed changes, remains in its infancy.