A new pattern of cerebellar hemorrhages in preterm infants

Objective. Posterior fossa hemorrhages may be underdiagnosed in surviving n eonates, with cerebellar hemorrhage discovered in 10% to 25% of autopsy spe cimens from very low birth weight infants. Posterior fossa lesions have bee n difficult to visualize by the traditional ultrasonography approach throug h the anterior fontanelle. Late in 1994, routine posterior fossa imaging th rough the posterolateral fontanelle was instituted to improve the ultrasono graphic visualization of the posterior fossa in neonates. Methods. Infants identified with posterior fossa hemorrhage by cranial ultr asonography between 1994 and 1996 were followed prospectively through disch arge and their clinical courses reviewed. Infants diagnosed with posterior fossa hemorrhage between 1991 and 1994 were identified retrospectively from a comprehensive radiology database to use in comparison. All infants survi ving to discharge were entered into neurodevelopmental follow-up using stan dard developmental assessments. Results. Approximately 525 infants underwent cranial sonography during the study period between October 1994 and September 1996, including 250 infants weighing <1500 g. Thirteen infants were identified with posterior fossa he morrhage using the posterolateral fontanellar approach. In contrast, only 2 infants were identified with posterior fossa hemorrhage between 1991 and 1 994 using traditional anterior fontanellar views. Six very low birth weight infants were identified with cerebellar hemorrhages not associated with su pratentorial, intraventricular hemorrhage. Each hemorrhage had a clinically silent presentation and, in 5 infants, was not well-appreciated by anterio r fontanellar images. Magnetic resonance imaging studies were performed on 5 of the 6 infants and confirmed a cerebellar lesion in the area of previou s echo density on ultrasonography. No infant is exhibiting motor abnormalit ies on neurologic examination, although 4 infants are demonstrating cogniti ve, developmental delay. Follow-up, however, is limited to a corrected age of less than or equal to 48 months. Discussion. Cerebellar hemorrhage is an underrecognized and poorly visualiz ed complication in preterm infants. Consistent imaging via the posterolater al fontanelle may demonstrate cerebellar hemorrhage missed by the anterior fontanellar approach. Cerebellar hemorrhage in low birth weight infants may be clinically silent and not associated with a significant supratentorial hemorrhage. These infants may survive to discharge. Long-term neurodevelopm ental follow-up is necessary to establish the ultimate outcome of these inf ants. Future prospective study, using posterolateral fontanellar imaging, m ay elucidate further the pathophysiology of cerebellar hemorrhage in low bi rth weight infants.