Congenital Cerebellar Malformation

Congenital Cerebellar Malformation
Bernadette L. Koch, MD
DIFFERENTIAL DIAGNOSIS
Common
  • Chiari 1 Malformation
  • Chiari 2 Malformation
Less Common
  • Cerebellar Hypoplasia
  • Cerebellar Dysplasias (Unclassified)
  • Dandy-Walker Spectrum
Rare but Important
  • Rhombencephalosynapsis
  • Molar Tooth Malformations (Joubert)
  • Chiari 3 Malformation
ESSENTIAL INFORMATION
Helpful Clues for Common Diagnoses
  • Chiari 1 Malformation
    • Key facts: Caudal protrusion of pointed cerebellar (CB) tonsils, below foramen magnum (FM)
      • Normal CB tonsils rounded
      • CB position below “opisthion-basion line”: 1st decade (6 mm), 2nd-3rd decade (5 mm), 4th-8th decade (4 mm), and 9th decade (3 mm)
      • Underdeveloped bony posterior fossa → downward hindbrain herniation
    • Imaging
      • CB tonsils low and pointed; CSF at foramen magnum effaced; small bony posterior fossa
      • Cine MR: Motion of CB tonsils
      • ± syrinx, presyrinx edema, or ventriculomegaly
      • ± short clivus, dorsal tilt of dens, craniovertebral anomalies
      • Rarely develop over time; rarely resolve without treatment
  • Chiari 2 Malformation
    • Key facts
      • ˜ 100% associated with open neural tube defect, usually myelomeningocele
      • ↓ incidence with ↑ in folate replacement
    • Imaging
      • Small posterior fossa, large FM
      • Large funnel-shaped foramen magnum
      • “Cascade” or “waterfall” herniation of tissue downward, behind medulla
      • “Peg” = uvula/nodulus/pyramid of vermis
      • Cervicomedullary “kink”
      • “Towering” cerebellum through incisura → compressed “beaked” tectum
      • 4th ventricle elongated, without fastigium (posterior point)
      • Low insertion of tentorium/torcular
      • ± syringohydromyelia (20-90%)
      • ± corpus callosum dysgenesis (90%)
      • ± posterior arch C1 anomalies, diastematomyelia, Klippel-Feil syndrome
      • ± aqueduct stenosis, GM heterotopia, absent septum pellucidum/fused forniceal columns, stenogyria
Helpful Clues for Less Common Diagnoses
  • Cerebellar Hypoplasia
    • Key facts: Inherited or acquired, isolated or syndromic
    • Imaging
      • Isolated small CB hemisphere(s) with normal fissures and interfoliate sulci
      • + brainstem hypoplasia = pontocerebellar hypoplasia
      • ± vermian hypoplasia, abnormal CB fissures, cortical dysplasia
      • ± Dandy-Walker spectrum, molar tooth syndromes, rhombencephalosynapsis
      • Presence of gliosis suggests atrophy rather than congenital hypoplasia
  • Cerebellar Dysplasias (Unclassified)
    • Key facts: Developmental abnormality
    • Imaging
      • CB hemispheres &/or vermis; abnormal orientation of fissures and lobules
      • Affected structure usually small
      • Focal or diffuse, single or multiple, unilateral or bilateral
      • Diffuse usually associated with supratentorial anomalies: Congenital muscular dystrophies, lissencephalies, polymicrogyria
  • Dandy-Walker Spectrum
    • Key facts: Continuum = “classic” Dandy-Walker malformation (DWM) → CB vermian hypoplasia → Blake pouch cyst (BPC) → mega cisterna magna (MCM)
      • Intelligence normal in up to 50% of “classic” DWM cases
    • Imaging
      • “Classic” DWM: Cystic dilatation of 4th ventricle → large posterior fossa, torcular-lambdoid inversion, superiorly rotated hypoplastic vermis
      • CB vermian hypoplasia: Vermis hypoplasia ± upward rotation; normal-sized posterior fossa and brainstem
      • BPC: Herniation of inferior 4th ventricle through foramen of Magendie into vallecula and retrovermian cistern; enhancing choroid plexus in cyst wall
      • MCM: Enlarged pericerebellar cisterns communicate with basal subarachnoid spaces; normal vermis/4th ventricle; cistern crossed by falx cerebelli
      • Imaging cannot precisely distinguish between mild DWM, BPC, and MCM
      • ± associated callosal anomalies, cortical dysplasia, heterotopia
Helpful Clues for Rare Diagnoses
  • Rhombencephalosynapsis
    • Key facts
      • Fusion of CB hemispheres, dentate nuclei, and superior CB peduncles
    • Imaging: Complete or partial fusion CB hemispheres
      • Absent primary fissure on sagittal; transverse folia on axial and coronal; keyhole-shaped 4th ventricle on axial
      • Fused horseshoe-shaped dentate nuclei
      • Absent posterior CB notch and vallecula
      • Absent or severely hypoplastic vermis
      • ± absent septum pellucidum, olivary hypoplasia, anomalies of limbic system, multiple cranial suture synostoses
      • ± corpus callosum dysgenesis, aqueductal stenosis, cortical dysplasia
  • Molar Tooth Malformations (Joubert)
    • Key facts: Joubert anomaly is prototype
      • Joubert patients present with episodic hyperpnea, abnormal eye movements, ataxia, and mental retardation
      • Identical imaging findings in some patients without classic Joubert syndrome symptoms; some with renal or ocular anomalies, hepatic fibrosis/cysts, hypothalamic anomalies
    • Imaging: “Molar tooth” = large superior CB peduncles (do not decussate in dorsal midbrain) on axial images
      • Sagittal: Small, high CB vermis
      • Coronal: “Split vermis”
      • Axial: Small dysplastic vermis → triangular-shaped mid 4th ventricle and bat wing-shaped superior 4th ventricle
  • Chiari 3 Malformation
Tags:
Aug 10, 2016 | Posted by in PEDIATRICS | Comments Off on Congenital Cerebellar Malformation

Full access? Get Clinical Tree
Get Clinical Tree app for offline access