Defect in skull with protrusion of intracranial structures

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  Encephalocele: Cerebrospinal fluid (CSF), brain tissue, and meninges

  
  
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  Meningocele: Meninges and CSF

Bony defect should be demonstrated

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  Occipital defect most common and is posterior midline

  
  
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  Parietal defect usually midline and higher

Other CNS anomalies common, including ventriculomegaly (70-80%) and microcephaly (25%)

Amniotic band syndrome

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  May cause cranial defect and cephalocele

  
  
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  Other body parts often affected, especially extremities

Cystic hygroma: Cranium intact

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  Septated cystic neck mass; hydrops common

  
  
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  In early pregnancy, cystic hygroma often misdiagnosed as cephalocele and vice versa

Associated with multiple syndromes

Meckel-Gruber most common genetic disorder

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  Encephalocele, polydactyly, polycystic kidneys

Always image from several directions to exclude edge artifact, which may mimic calvarial defect

Use endovaginal sonography in 1st trimester if any suggestion of irregular head contour transabdominally

Look carefully for bands as possible cause

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  Roll patient to side to see if fetus remains in fixed position

Look carefully for other anomalies, which may identify specific syndrome