Neurodevelopmental outcome after antenatal diagnosis of posterior fossa abnormalities.

Posterior fossa abnormalities are sonographically diagnosable in the fetus. Anomalies of this region include Dandy-Walker malformation, enlarged cisterna magna, and arachnoid cyst. Despite prenatal diagnosis, the uncertainties related to natural history and neurodevelopmental outcome in survivors make patient counseling difficult. The purposes of this study were to determine the accuracy of prenatal diagnosis of these lesions and elucidate long-term neurodevelopmental outcome in survivors in prenatally diagnosed posterior fossa abnormalities. Fifteen cases of posterior fossa abnormalities were reviewed. Antenatal diagnoses of Dandy-Walker malformation was made in 13 of these cases, arachnoid cyst in one case, and enlarged cisterna magna in one case. Hydrocephalus was present in 66% of patients. The sonographic diagnosis was concordant with the pathologic or neonatal radiologic diagnosis in 13 of 15 cases. Seven fetuses (47%) exhibited additional cranial or extracranial anomalies. A karyotypic abnormality (trisomy 18) was found in one of 15 cases of posterior fossa abnormalities. Neurodevelopmental delay was present in 80% of survivors with follow-up study to 4 years of age. Prenatal diagnosis of posterior fossa abnormalities is highly accurate, yet the differential diagnosis can be challenging. Cognitive and psychomotor developmental delays remain commonplace despite early diagnosis and treatment. The approach with families in cases of prenatal diagnosis of posterior fossa abnormalities should include a search for additional central nervous system and extra-central nervous system anomalies in the fetus and counseling of parents regarding potential adverse outcome for survivors.