Hosting 728 files, 2951 images, and 4 contributors.

Random Case

Joseph Junewick, MD FACR
over 11 years ago
Enter A Workflow
Standard2   Academic2

Please choose a workflow. A standard workflow allows you to browse the repository with full case detail; the academic workflow allows you to browse the repository with limited case detail revealed. Double click on the images to launch image viewer.

ARSt Case Repository


Case Detail

Anatomy: Brain-Spine
Joseph Junewick, MD FACR
Diagnostic Category: Developmental or Congenital
Created: 11 months ago
Updated: 11 months ago
Tags: PEDS
Modality/Study Types: MR
Adobe32 PDF Imagej32 ImageJA


3 year old male with esotropia, apraxia and frequent falls

Case Images




-Vermian agenesis
-Fusion of cerebellar hemispheres
-Fusion of dentate nuclei


The rhombencephalon is the most caudal of the early three primary brain vesicles and eventually divides to form the adult pons, medulla, and cerebellum. Embryonic development of the cerebellum is traditionally explained to begin with proliferating neuroblasts from the alar plates forming paired rhombic lips. These structures thicken and extends progressively toward the midline. At the end of the 12th week of gestation, the fusion of these rhombic lips at the midline begin rostrally, with the anterior vermis forming prior to the posterior vermis.

Rhombencephalosynapsis is a cerebellar anomaly caused by vermian maldevelopment, showing fusion of the cerebellar hemispheres, middle cerebellar peduncles, and the dentate nuclei. This anomaly is characterized by an absence of the anterior vermis and a deficiency of the posterior vermis, with the nodulus likely formed. A distinction from other pathologies such as Dandy-Walker malformation, Joubert syndrome, or tectocerebellar dysgraphia lies in the fact that this vermian hypogenesis or agenesis is not associated with disconnected cerebellar hemispheres.

Clinical manifestations depend on the extent of posterior fossa findings. Some patients may be asymptomatic if rhombencephalosynapsis is an isolated finding. However, supratentorial abnormalities which occur at the time the cerebellum is developing often can dominate clinical presentation. General symptoms include mental retardation, ataxia, spasticity, and epilepsy. Congenital hydrocephalus secondary to aqueductal stenosis is a known association with this anomaly.

Instead of a normal crescent-shaped fourth ventricle, a characteristic finding of rhombencephalosynapsis is a diamond-shaped fourth ventricle on axial MRI. Other features revolve around fused cerebellar hemispheres, which include a flat, uninterrupted base of the cerebellar hemispheres; transverse orientation of folia in the inferior cerebellum; and a large corpus medullare. Features that may be present are deficiency or absence of septum pellucidum, dysgenesis of the corpus callosum and the anterior commissure, fused fornices, and fused thalami.


Utsunomiya H, et al. Rhombencephalosynapis: Cerebellar Embryogenesis. AJNR 19:547-549 (1998)


Andrew Nguyen

Corporate Office: 616.363.7272, 3264 North Evergreen Drive, Grand Rapids, MI 49525

Spectrum Health Helen Devos Childrens Hospital GE HealthCare