Abstract
Rhombencephalosynapsis (RS) is a rare and sporadic cerebellar malformation characterized
by agenesis of cerebellar vermis, fusion of the cerebellar hemispheres, dentate nuclei,
and superior cerebellar peduncles. In majority of cases, RS is associated with wide
range of cerebral malformations (dysgenesis or agensis of corpus callosum (ACC) and
anterior commissurae, fusion of the inferior colliculi, cerebral peduncles, or thalami
and hydrocephalus). A third gravida with 32 weeks of pregnancy was evaluated for hydrocephalus.
The fetus had teardrop lateral ventricles, colpocephaly, upward displacement of third
ventricle with abnormal posterior fossa, and an abnormal cerebellum formed by partly
fused cerebellum in a single block with no individualization of the vermian structure
suggestive of complete ACC with RS. Fetal MRI showed teardrop lateral ventricles,
upward displacement of the third ventricle and colpocephaly partially fused cerebellar
hemispheres, and no visualization of separate and distinct vermis with suspected fused
superior cerebellar peduncles corroborating the ultrasound findings of complete ACC
and partial RS. The baby had a very difficult postnatal course and succumbed on postnatal
day 4. Prenatal diagnosis of RS and ACC is of utmost importance for prenatal counseling,
as these abnormalities are uncorrectable and in most of the cases carries poor prognosis.
Keywords
Rhombencephalosynapsis - Agenesis - Vermis - Fusion - Dentate - Superior - Peduncles
