Fluid-Filled Calvarium



Fluid-Filled Calvarium


Roya Sohaey, MD



DIFFERENTIAL DIAGNOSIS


Common



  • Severe Hydrocephalus


  • Holoprosencephaly Spectrum


  • Hydranencephaly


Less Common



  • Dandy-Walker Continuum: Classic


  • Severe Schizencephaly


Rare but Important



  • Large Arachnoid Cyst


  • Large Glioependymal Cyst


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • Routine lateral ventricle measurement



    • Measure atria



      • At level of choroid plexus glomus


      • Inner-to-inner wall measurement


    • Normal is < 10 mm between 14-40 wks


  • Routine brain anatomy assessment



    • Falx


    • Cavum septi pellucidi


    • Thalamus


    • Choroid plexus


    • Cerebellum


    • Cisterna magna


  • Use vaginal ultrasound if fetus cephalic


  • MR helpful for differential diagnosis


Helpful Clues for Common Diagnoses



  • Severe Hydrocephalus



    • > 15 mm lateral ventricular (LV)


    • Thin cortical mantle



      • Compressed by ventricles


    • “Dangling” choroid



      • Choroid does not fill LV


      • Bilateral “dangling” if opposite choroid falls through foramen of Monro


    • Cavum septi pellucidi often absent



      • Fenestrations in wall from ↑ pressure


    • Macrocephaly if obstructive cause


    • Causes



      • Aqueductal stenosis


      • Dandy-Walker continuum


      • Chiari II malformation


  • Holoprosencephaly Spectrum



    • Early arrest of brain cleavage and rotation



      • Variable severity


    • No clear division between different types



      • Alobar (most severe)


      • Semilobar (intermediate type)


      • Lobar (subtle)


    • Ventricle findings



      • Monoventricle


      • Dorsal sac


    • Variable absent midline structures



      • Cavum septi pellucidi


      • Falx


      • Corpus callosum


      • 3rd ventricle


      • Variable fused thalamus


    • Brain mantle appearance



      • “Pancake”: Flat at skull base


      • “Cup”: Partially surrounds monoventricle


      • “Ball”: Mantle surrounds monoventricle


    • Associated facial anomalies



      • Hypotelorism image cyclopia


      • Abnormal nose image proboscis


      • Median or bilateral cleft lip/palate


    • Associations



      • Trisomy 13 (most common)


      • Trisomy 18


      • Maternal diabetes


  • Hydranencephaly



    • Complete cerebral hemisphere destruction


    • Etiology



      • Vascular occlusion


      • Hemorrhage


      • Hypotension


      • Infection


    • Imaging features



      • Absent cerebral hemispheres


      • Present falx


      • Normal posterior fossa


      • Normal or splayed thalamus


      • Variable head size


      • No flow in middle or anterior cerebral arteries


Helpful Clues for Less Common Diagnoses



  • Dandy-Walker Continuum: Classic



    • Dysgenesis of cerebellar vermis



      • Absent


      • Severely hypoplastic


    • Cystic dilatation of 4th ventricle



      • Ventricle communicates with cisterna magna


      • Posterior fossa cyst


    • Associated brain findings



      • Agenesis of corpus callosum


      • Hydrocephalus



      • Encephalocele


      • Neural tube defect


    • Careful with diagnosis before 18 wks



      • Vermis not fully formed < 18 wks


      • Normal 1st trimester rhombencephalon is large and cyst-like


  • Severe Schizencephaly



    • Brain cleft



      • Wedge-shaped defect


      • Filled with cerebrospinal fluid (CSF)


      • Extends from ventricle to brain surface


      • Lined with gray matter


    • Most common in cerebral hemispheres



      • Unilateral in 60%


      • Bilateral in 40%


    • Variable size


    • Associated brain anomalies



      • Absent cavum septi pellucidi


      • Septo-optic dysplasia


      • Heterotopia


      • Polymicrogyria


      • Pachygyria


    • Etiology



      • Neuronal migration anomaly


Helpful Clues for Rare Diagnoses

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Aug 10, 2016 | Posted by in OBSTETRICS | Comments Off on Fluid-Filled Calvarium

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