Microcephaly



Microcephaly


Anne Kennedy, MD



DIFFERENTIAL DIAGNOSIS


Common



  • Idiopathic


  • Symmetric IUGR


  • Exencephaly, Anencephaly


Less Common



  • Encephalocele


  • Atelencephaly, Aprosencephaly


  • Destructive Processes


Rare but Important



  • Syndromes



    • Cornelia de Lange Syndrome


    • Neu Laxová Syndrome


  • Teratogens



    • Fetal Alcohol Syndrome


    • Hydantoin Syndrome


    • Valproic Acid


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • Ensure that measurements are obtained correctly


  • Repeat measurement for confirmation


  • Look at parents and consider measuring parental head circumference


  • Is the whole fetus small or just the head?



    • If all measurements are small consider incorrect dates versus early onset growth restriction


    • If head measurements smaller than other parameters, true microcephaly more likely


  • Is there a cranial vault?


  • Is there a defect in the vault?


  • Is the face normal?



    • Atelencephaly/aprosencephaly strongly associated with abnormal facies


  • Are there calcifications?



    • Good predictor of infection but may be subtle: Small, non-shadowing


    • Use transvaginal scans for improved resolution if fetus in cephalic presentation


  • Is there evidence of bleeding?



    • Look for echogenic clot in ventricles, nodular ependymal thickening, porencephaly


  • Is the maternal serum alpha fetoprotein elevated?



    • Encephalocele, anencephaly, exencephaly most likely


Helpful Clues for Common Diagnoses



  • Idiopathic



    • Small head size with normal interval growth


    • Structurally normal fetus


    • Structurally normal brain


  • Symmetric IUGR



    • Size less than expected for dates


    • All biometric parameters affected


    • Often early onset


    • More likely due to intrinsic fetal abnormality than placental insufficiency


    • Look for signs of aneuploidy/syndromes


  • Exencephaly, Anencephaly



    • Cranial vault absent


    • Variable amounts of brain tissue present


    • Short crown rump length in first trimester


    • In exencephaly the externalized brain may confer spiky or lobulated contour to head


    • “Frog eye” appearance of large, shallow orbits and absent vault above orbital ridge


    • Look for amniotic bands as cause



      • Linear echoes in amniotic fluid


      • Constriction/amputation defects in extremities


      • “Slash” defects elsewhere (e.g., abdominoschisis, facial cleft)


Helpful Clues for Less Common Diagnoses



  • Encephalocele



    • If large amount of brain parenchyma in encephalocele, skull vault is small



      • Microcephaly in 25% of occipital encephaloceles


    • Diverse appearance of herniated tissue



      • Gyral pattern may be identified


    • Look for osseous defect


    • Look for associated anomalies for syndromic diagnosis



      • Meckel Gruber syndrome associated with abnormal kidneys/polydactyly


  • Atelencephaly, Aprosencephaly



    • Developmental arrest of formation of telencephalon &/or prosencephalon


    • No normal cerebral structures


    • Cerebellum often hypoplastic


    • Facial anomalies, often severe



      • Absent eyes/nasal structures, midline oculofacial defects including cyclopia


    • Radial ray anomalies including absent thumbs



    • Oligodactyly, camptodactyly, clinodactyly, clubfoot


  • Destructive Processes



    • Look for calcifications in TORCH infections


    • Infarction/hemorrhage/ischemic “steal” phenomena in arteriovenous shunts



      • Use Doppler to evaluate all “cystic” structures for flow


    • MR helpful to show blood products


    • MR helpful to demonstrate encephalomalacia, porencephalic cysts


Helpful Clues for Rare Diagnoses

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Aug 10, 2016 | Posted by in OBSTETRICS | Comments Off on Microcephaly

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