The intracranial translucency (IT) is a recently introduced marker of open spina bifida (OSB). In this study, we describe a case of a fetus affected by Blake’s pouch cyst which showed alterations of BS/BSOB ratio at the first trimester screening. 1. Introduction Intracranial translucency (IT) is an open spina bifida (OSB) marker at first trimester scan introduced by Chaoui et al. [1, 2]. IT represents the future 4th ventricle and its obliteration or reduction of its thickness is present in fetuses affected by OSB. This data is subject to ample discussion [3–5]. Recent studies show that the parameter, which best indicates the OSB risk, is the inversion of the thickness ratio between BS (brain stem) and brain stem to occipital bone distance (BSOB) BS/BSOB [6]. Numerous studies highlight the alteration of IT in several pathologies of the posterior fossa [6–9]. Nizard et al. [7] report four cases of fetuses with Dandy Walker syndrome, with posterior fossa changes starting the first trimester and demonstrating enlarged IT. Other recent publications confirm this observation [8–10]. Recently Lafouge et al. [11], reported enlarged IT in a fetus with Blake’s pouch cyst (BPC). Garcia-Posada et al. reported 2 cases of BPC, and they described the Cisterna Magna (CM) which was enlarged [12]. We report a new case of BPC, in which the posterior fossa images of first trimester have been evaluated. 2. Case Report A 29-year-old patient, G3 P1, underwent 1st trimester aneuploidy screening at weeks of gestation (Figure 1). The crown-rump length was 52？mm, nuchal translucency was 1.1？mm, and the combined risk for trisomy was 21 < 1/10,000. At 21 weeks, the patient returned for suspected diagnosis of enlarged CM. At the ultrasound scan a connection between the CM and the 4th ventricle was evident and in the sagittal plane the cerebellar vermis was rotated. However, its biometry was normal [13]. The brainstem-vermis angle and brainstem-tentorium angle was determined by the method of Volpe et al. [14] and Ghi et al. [15]. Persistent BPC was diagnosed. Magnetic resonance was performed and the ultrasound diagnosis was confirmed (Figure 2). The pregnancy concluded uneventfully and the neonate showed normal neurological findings at birth. The neonatal transfontanellar ultrasound confirmed the prenatal diagnosis. At one month he has regular psychomotor development. Figure 1: Fetal ultrasound image (sagittal view) at weeks of gestation, showing an enlarged intracranial translucency (IT) in the posterior fossa, the brain stem (BS), and the cisterna magna (CM). Figure 2: Second
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