Fetal intracranial cysts: prenatal diagnosis and outcome

Intracranial cysts are central nervous system malformations involving different brain regions, and commonly diagnosed during prenatal period by ultrasound scan (US). A malformative cyst is a nontumoral fluid-filled collection exerting a mass effect on the brain parenchyma and/or on the ventricles, regardless of its location within subarachnoid spaces, brain or ventricles, and of the nature of its limiting membrane, which is always unknown prenatally. Although a large number of case reports have been published, many uncertainties remain concerning their epidemiology, pathogenesis, and outcome. Most of these lesions, if not associated with other fetal anomalies, are benign in nature, remain clinically silent, do not evolve or even frequently regress spontaneously and do not impair physiologic neurodevelopment. The normality of the adjacent brain is the major argument in favour of a malformative lesion. The correct diagnosis is of crucial importance to exclude the presence of other rare lesions (e.g. cystic neoplasms or intracranial hemorrhage) that could negatively affect neurodevelopmental outcome of the child. To establish a correct prognosis all efforts must aim to precisely interpret the US images accurately analyzing the brain anatomy.