Sensitivity of Foetal MRI in Studying the Germinal Matrix: Comparison with Autopsy

Abstract

Our study aimed to combine in vivo foetal cerebral magnetic resonance findings and histopathological analysis to chart details of the development and characteristics of the germinal matrix not disclosed by ultrasound, and to establish standard normal parameters for in vivo investigation. We enrolled pregnant women between the 18^th and 23^rd weeks of gestation awaiting voluntary termination of pregnancy. The patients had a foetal cerebral magnetic resonance scan and the aborted foetus subsequently underwent autopsy. Both investigations focused on the germinal matrix, measured at the floor of the lateral ventricles, to disclose any impairment of neuronal migration. Three foetuses were chosen for the study, one presented CMV infection with multiorgan involvement disclosed at autopsy. The brain, however, did not show signs of infection but presented impaired sulcal formation compared to brains of the same gestational age. This finding had not been disclosed by MRI. The study is still underway but our preliminary findings show that magnetic resonance clearly displays the germinal matrix and can measure its thickness but does not yield accurate information on sulcal formation early in pregnancy. Autopsy subsequently demonstrated that failure of neuronal migration in the foetus results in a thicker germinal matrix whereas the cortex is thinner and underdeveloped. This finding emphasizes that migration abnormalities are not disclosed by MRI confined to macroscopic assessment of sulcal formation, especially in the early stages of pregnancy (18–22 weeks), but can be suspected and indirectly diagnosed by measurement of germinal matrix thickness. Our study showed that MRI is highly sensitive in identifying the germinal matrix and cerebral cortex and can measure these structures to yield new information for the diagnosis of impaired neuronal migration.