[Cranial ultrasound through posterolateral fontanelle in visualization of posterior fossa abnormalities in preterm and term neonates].

Objectives: The aim of the study was to evaluate the usefulness of US in the diagnosis of posterior fossa abnormalities in neonates by posterolateral fontanelle as compared with the anterior fontanelle approach and MRI. Material and methods: US studies were performed on 1337 neonates, including 512 preterm infants, through the anterior and posterolateral fontanelles. Abnormalities were detected in 134 patients. Among them, abnormalities in posterior fossa were visualized with the posterolateral approach in 14 neonates. MR images were obtained in that subgroup. Results: The lesions consisted of cerebellar hemorrhage and congenital cerebellar malformations. Foci of hemorrhage were visualized by US in preterm neonates (n = 5), only through the posterolateral approach and on MRI Dandy-Walker malformations (n = 2) were detected by US with both approaches and confirmed on MRI In pontocerebellar hypoplasia (n = 2), US with both approaches, showed hypoplastic cerebellar hemispheres and fluid in the posterior fossa. MRI, additionally visualized pontine hypoplasia. Fluid collection in the posterior fossa and translocation of cerebellar hemispheres were observed in the other 6 neonates by US with both approaches. MRI revealed arachnoid cysts (n = 2), mega cistema magna (n = 3) and Blake's pouch (n = 1). Conclusions: US using posterolateral fontanelle is the method of choice for the diagnosis of cerebellar hemorrhage. These lesions are not visualized through anterior fontanelle. US visualization of the abnormal structures in some cerebellar malformations has similar effectiveness for both approaches. MRI plays the crucial role in identification and differential diagnosis of these malformations.