Changes in appearance of cortical formation abnormalities in the foetus detected on sequential in utero MR imaging

ObjectivesWe describe 64 foetuses with cortical formation abnormalities (CFA) who had two in utero magnetic resonance (iuMR)exams, paying particular detailto those in which the original classification of CFA category changed between the two studies. Thegoal was to attempt to quantify the value of third-trimester follow-up studies in CFA foetuses on second-trimester iuMR imaging.MethodsThe 64 foetuses reviewed came from a CFA cohort of 374 foetuses reported in an earlier publication, which detailed aclassification for foetal CFA. A consensus panel of senior paediatric neuroradiologists reviewed both studies, described anychange in the category of CFA between them, and attempted to predict the possible clinical significance of any differences basedon the combined clinical experience of the panel.ResultsIn 40/64 (62%) foetuses, the CFA description was the same on both studies. In 24/64 (38%) cases, there was a categorychange which included three foetuses without CFA on first examination, six foetuses where the difference involved change inlaterality/symmetry, and in 15 cases the re-classification involved categorical change within the same group. Brain abnormalitiesother than CFA were present in 30/64 (47%) foetuses on the first study and in 33/64 (52%) on the second. We predicted thatprognosis would have changed on the basis of the second study in 8% of cases, all indicating worse prognosis.ConclusionsWe have shown that the extra diagnostic and predicted prognostic yield justifies follow-up studies in the thirdtrimester if a CFA is shown on the second-trimester iuMR imaging.