Diagnostic assessment of foetal brain malformations with intra-uterine MRI versus perinatal post-mortem MRI.

PURPOSE: To evaluate differences in diagnostic yield of intra-uterine foetal (iuMR) and post-mortem MRI (PMMR) for complex brain malformations, using autopsy as the reference standard. METHODS: In this retrospective, multicentre study spanning 2 years, we reviewed 13 terminated singleton pregnancies with a prenatal ultrasound finding of complex foetal cerebral abnormalities, referred for both iuMR and PMMR. The iuMR and PMMR studies of the brain were reported independently by two groups of radiologists, blinded to each other's reports. Descriptive statistics were used to compare differences in intracranial abnormalities with autopsy (and genetic testing, where present) as reference standard. RESULTS: The median gestational age at termination was 24.6 weeks (IQR 22-29) with median time between delivery and PMMR of 133 h (IQR 101-165). There was full concordance between iuMR and PMMR findings and autopsy in 2/13 (15.3%) cases. Partial concordance between both imaging modalities was present in 6/13 (46.2%) and total discordance in the remainder (5/13, 38.5%). When compared to autopsy, PMMR missed important key findings specifically for neuronal migration and cerebellar anomalies, whereas iuMR appeared to overcall CSF space abnormalities which were less crucial to reaching the final overall diagnosis. CONCLUSIONS: iuMR should be performed to improve foetal phenotyping where there is a prenatal ultrasound for complex foetal brain abnormalities. Reliance on PMMR alone is likely to result in misdiagnosis in a majority of cases.

Echogenic cavum septi pellucidi is associated with mild callosal dysgenesis on postnatal MRI.

We present a previously unreported association between the sonographic finding of an echogenic cavum septi pellucidi (CSP), concurrent hypointense signal within the CSP on fetal MRI and postnatal MR evidence of dysgenesis of the rostrum and genu of the corpus callosum as well as abnormal shortening of the septal leaflets. An echogenic or non-fluid filled CSP in the fetus at the midtrimester ultrasound is likely to represent a form of mild callosal dysgenesis. Perinatal assessment of vision and endocrine function and clinical follow-up of neurodevelopment and growth are probably indicated in such cases.

Effect of prior cognitive state on resting state networks measured with functional connectivity.

To address the extent to which functional connectivity measures an absolute brain state, we observed the effect of prior performance of a language task on resting-state networks in regions associated with language. Six subjects were imaged during rest before and after a block-design language task. Connectivity maps were generated for each of four language regions (identified from analysis of the language activation portion of the study) in each subject for both rest periods. Conjunction analysis demonstrated distinct networks of voxels for each seed region, indicating separate functional subnetworks associated with the different regions. In a comparison of rest before and after the activation task widespread and significant changes were observed in all individuals, suggesting that the measured resting state network reflects a dynamic image of the current brain state. At the group level, an extended network was observed that was largely persistent over time. Even at the group level an increase in connectivity was observed between left and right middle frontal gyri, and between posterior cingulate cortex and medial frontal cortex in the rest after the language task. These results suggest that functional connectivity may be a powerful measure of cognitive state, sensitive to differences between controls and patients together with the particular cognitive processing occurring during the rest state.