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

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