= rare genetic disorder affecting cerebellum

• hypotonia, ataxia
• neonatal breathing dysregulation: episodic hyperpnea
• ocular motor apraxia (abnormal eye movement)
• mental retardation (intellectual disability) of variable severity = global cognitive developmental delay

Genetics: autosomal recessive disorder with 25% recurrence risk; >8 causative gene mutations

Systemic involvement:

• nephronophthisis
• congenital hepatic fibrosis
• coloboma, retinal dystrophy
• various forms of polydactyly

Related disorders:

COACH (cerebellar vermis hypoplasia / aplasia, oligophrenia, ataxia, ocular coloboma, hepatic fibrosis) syndrome

CORS (cerebello-oculo-renal syndrome)

OFD6 (oro-facial-digital syndrome type 6)

Path:

1. nearly total aplasia of cerebellar vermis
2. dysplasia + heterotopia of cerebellar nuclei
3. near total absence of pyramidal decussation
4. anomalies in structure of inferior olivary nuclei, descending trigeminal tract, solitary fascicle, dorsal column nuclei

• “molar tooth sign” on AXIAL image (virtually PATHOGNOMONIC):
  • elongated thickened horizontally oriented superior cerebellar peduncles
  • deep interpeduncular fossa
  • vermian hypoplasia / dysplasia
• change in shape of 4^th ventricle: triangle-shaped at mid-level + bat-wing–shaped superiorly
• cerebellar hemispheres appose one another in midline
• superior cerebellar peduncles surrounded by CSF
• small isthmus + midbrain in AP diameter ← absence of decussation of superior cerebellar peduncles
• brainstem abnormalities:
  • dysmorphic tectum + midbrain
  • thickened elongated midbrain + small pons
• supratentorial abnormalities (30%):
  • callosal dysgenesis, cephaloceles, hippocampal malrotation, migrational disorders, ventriculomegaly

Prognosis: renal + hepatic disease responsible for mortality

DDx: Dandy-Walker malformation