The value of fetal MRI (fMRI) compared to ultrasound in the prenatal detection of CNS abnormalities and impact on counseling were determined in 25 pregnant women examined at University of Dusseldorf, Germany. Examination time was 27 to 51 minutes (41.8+/-6.1 min). Results were correlated with postnatal MRI, ultrasound and clinical follow-up. fMRI was performed 3-10 days after ultrasound between gestational week 22 and 34 (GW 26.1+/-3.6). Abnormalities suspected on fetal ultrasound were confirmed by fMRI in 8 cases. These included 2 cases of aqueductal stenosis hydrocephalus, and 1 each of hemimegalencephaly, microlissencephaly, ventriculomegaly, schizencephaly, brain tumor, and corpus callosum agenesis. Additional diagnoses or exclusions of suspected findings were established in 13 cases. The exclusions were corpus callosum agenesis in 4 cases and myelomeningocele, vermial aplasia, aqueductal stenosis, and Dandy-Walker malformation in 1 case each. Diagnoses were completely revised by fMRI in 4 cases. Postnatal MRI confirmed the fMRI findings in 11 patients. The quality of fMRI is technically comparable to postnatal MRI, and surgical treatment options are better defined than with ultrasound alone. 
COMMENT. fMRI is superior to fetal ultrasound in detection of congenital CNS abnormalities. In institutions with trained professionals, fMRI is recommended in addition to ultrasound in patients with suspected pathologies that may require surgical interventions and parent counseling.