Review article

Abstract

Enlargement of the cerebral ventricles can be caused by one of two main mechanisms: increase in pressure within the brain because of obstruction to the flow of fluid through and out of the ventricular system or primary loss of brain substance with normal or low intraventricular pressure. Accurate diagnosis is particularly important. In late pregnancy a larger than expected biparietal diameter as measured by ultrasound renders the diagnosis relatively easy. In earlier pregnancy one has to measure the ventricule/hemisphere (V/H) ratio. According to Campbell, a ratio greater than 0.5 after 18 weeks is a sufficient criterian. After 20 weeks the normal V/H ratio should be equal to or less than 0.33. It is vital to perform serial examinations particularly in high-risk patients because early absence of ventriculomegaly does not always preclude its later development. The natural history of such an enlargement in infants or adults is usually a progressive loss of brain function and mental deterioration. In fetuses the prognosis is much less well defined. Only about 50% do not have associated problems. Etiology is very often unprecise which makes prediction of the outcome very difficult. Regarding therapy, three options are available according to the phase of pregnancy when the diagnosis is made, to the extent of the disease and naturally according to the availability of modes of therapy: termination of pregnancy, withholding of therapy or active intervention in form of fetal surgery with percutaneous intrauterine placement of a ventricular shunt. Fetal surgery is a very new alternative with very precise indications and advantages but limited justifications at the moment.(ABSTRACT TRUNCATED AT 250 WORDS)