Data about the neurological prognosis of isolated cerebellar hypoplasia in utero are scant and inconsistent. In this monocentric retrospective study, we describe the neurodevelopmental outcomes in a series of children with isolated cerebellar hypoplasia of presumably hemorrhagic origin prenatally detected with fetal magnetic resonance imaging (fMRI). We retrospectively reviewed the charts of all the pregnant women who were referred for a neurological consultation, diagnosed with fetal encephalic malformation/disruption between 2010 and 2020 in the Fetal Therapy Unit of our institution. Fetal MRI (fMRI) was performed in all the pregnancies. Fetuses with cerebellar hypoplasia presumably of hemorrhagic origin were selected for the study. Fetuses exposed to alcohol or with additional malformations in other cerebral or body areas were excluded. All the infants received the postpartum follow-up care adopted in our center, including post-natal MRI, serial neurological examinations, standardized neurodevelopmental tests, and regular parental interviews. Cognitive functions were tested with GRIFFITHS II, WPPSI-III, and WISC-IV according to the child’s age. A total of 14 pregnant women out of 479 fetal consultations were eligible and included in the study group. In 57% of cases, the etiology of the hemorrhage was unknown. In 21% of cases, it was attributed to a blood transfusion, while in the remaining ones, it was attributed to maternal predisposing factors. Among the survivors, two infants were excluded for prematurity, and two were lost to follow-up. Ten patients were thus included in the study. Six patients had normal neurodevelopment and cognition, and three presented mild-moderate neurological signs, i.e., mild dyspraxia and visuoperceptual impairment. Only one child had a severe outcome, i.e., autism spectrum disorder. The cerebellum is particularly vulnerable to disruptions throughout its prolonged development. Extreme caution must be used in prenatal counseling considering that in the acute phase, lesion extension and vermis involvement can be overestimated with fMRI. In cases of uncertainty, performing an additional fMRI could be advisable after 4–8 weeks. However, in our series, infants with isolated cerebellar hypoplasia tended to have a favorable prognosis. Nevertheless, a long-term follow-up is needed and should include a postnatal brain MRI, serial neurological examinations, and neurodevelopmental tests at least up to school age.
