A newborn MRI shows absence of the corpus callosum with 'racing car' or 'steer horn' appearance of the lateral ventricles on coronal view, parallel-running non-converging lateral ventricles on axial view, and a midline interhemispheric cyst. Gyri are seen extending medially toward the third ventricle ('radial spoke' pattern). What is this diagnosis?

• A Holoprosencephaly (alobar type)
• B Dandy-Walker malformation
• C Schizencephaly
• D Agenesis of corpus callosum (ACC) ✓

Explanation

Agenesis of corpus callosum (ACC) has characteristic MRI features: parallel non-converging lateral ventricles (instead of normal convergent shape), colpocephaly (disproportionately enlarged occipital horns — 'teardrop ventricles'), 'steer horn' or 'race car' configuration of frontal horns on coronal view, widely spaced parallel gyri extending medially ('radial arrangement' toward the interhemispheric fissure), and often an interhemispheric cyst. Holoprosencephaly shows monoventricle with fused thalami. Dandy-Walker shows posterior fossa cyst with cerebellar vermis hypoplasia. Schizencephaly shows grey-matter-lined clefts.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.