Neuroimaging parameters in early open spina bifida detection. Further benefit in first trimester screening?

OBJECTIVE Morphological investigation of the central nervous system (CNS) in fetuses with positive markers for open spina bifida (OSB) detection, visualized by ultrasound during the first trimester of pregnancy. MATERIALS AND METHODS Data from fetuses that underwent routine first trimester ultrasound scan in our center during September 2007-March 2011 and presented abnormal aspects of the fourth ventricle, also referred as intracranial translucency (IT), provided the morphological support to evaluate CNS features. A neuro-histological study of posterior cerebral fossa illustrated anatomical features of the structures involved in the sonographic first trimester detection of neural tube defects. RESULTS Abnormal IT aspects were found in OSB cases examined in the first trimester, but also in other severe cerebral abnormalities. Brain stem antero-posterior diameter (BS) and brain stem to occipital bone (BSOB) ratio may be more specific for OSB detection. Correlations between histological aspects of posterior brain fossa and ultrasound standard assessment have been made; highlighting the anatomical features involved by the new techniques developed for OSB early detection. CONCLUSIONS Preliminary results show that modern sonographic protocols are capable to detect abnormalities in the morphometry of the posterior brain. First trimester fourth ventricle abnormalities should be followed by careful CNS evaluation because are likely to appear in OSB affected fetuses, but also in other CNS severe anomalies; in such cases, normal BS and BSOB ratio may serve as indirect argument for spine integrity, if specificity is confirmed in large series of fetuses.