Agenesis of corpus callosum (ACC)

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  Axial: Teardrop-shaped ventricles (colpocephaly)

  
  
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  Coronal: Texas Longhorn frontal horns

  
  
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  Sagittal: Loss of anterior cerebral artery branch pattern into pericallosal artery running along cingulate gyrus

Schizencephaly

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  Grey matter-lined, wedge-shaped defect extending from ventricle to brain surface

  
  
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  Lateral ventricle tented toward side of defect

Septooptic Dysplasia (SOD)

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  Frontal horns communicate: Flat top shape on coronal view

  
  
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  Attempt to use ocular globes as window to optic nerves in bony orbit

Holoprosencephaly spectrum

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  Often small head with abnormal round shape

  
  
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  Incomplete falx (deficient anteriorly in semilobar)

  
  
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  Fused fornices described as sign of lobar HPE

  
  
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  Sylvian fissures anteriorly displaced, meet on brain surface in syntelencephaly (middle interhemispheric fissure variant of HPE)

  
  
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  Isolated septal deficiency

  
  
  
  
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    Diagnosis of exclusion, final diagnosis will be postnatal with normal ophthalmology exam and endocrinology work-up

  
  

Cavum septi pellucidi (CSP) is marker of normal midline development

Absent CSP should trigger complete neurosonogram with high-resolution transducers and multiplanar images

Incorrect scan plane is common

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  CSP is box-shaped anechoic space with echogenic walls that interrupts midline echo between frontal horns

  
  
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  Differentiate from paired fornices: Parallel black and white lines without intervening fluid-filled space