Objective: To conduct a literature review to assess the effectiveness of first trimester ultrasonographic markers of spina bifida (SB) integrating data with our prospective experience.
Methods: The analysis of the SB cases that we prospectively detected in the first trimester, between January 2012 and February 2014, and a systematic review of all the papers evaluating the effectiveness of SB ultrasonographic markers at 11-14 weeks, namely brain stem diameter (BS), fourth ventricle/intracranial translucency (IT), cisterna magna (CM), brain stem/occipital bone distance (BSOB), the ratio between BS and BSOB. Some studies assess only the effectiveness of IT, others include more parameters, and few include them all.
Results: We prospectively detected four SB cases, three open (OSB) and one closed (CSB), in a low risk population undergoing first trimester screening. In the three OSB, CM (in 2/3 cases) and BSOB (3/3) distance were below the 5th percentile, BS and BS/BSOB ratio (3/3) were above the 95th percentile. In the CSB, all the measurements were within normal limits.
Conclusion: The literature and our data agree that most fetuses with OSB demonstrate in the first trimester positive sonographic markers in the posterior fossa, but additional prospective studies are needed to establish the best protocol for OSB screening.
Keywords: Brain stem; cisterna magna; first trimester screening; fossa; intracranial translucency; neural tube defect; posterior; ultrasound.