Classical Imaging in Callosal Agenesis.

Corpus callosal agenesis results in certain characteristic radiological appearances on magnetic resonance imaging. These classical named signs are revisited in this article.

Magnetic resonance imaging performed in an infant with enlarged head size was suggestive of a Dandy–Walker malformation with associated agenesis of the corpus callosum. The following classical radiological signs that have been described in literature[123] were seen.

Racing car sign: Axial imaging [Figure 1] shows the likeness of a Formula One car viewed from above with the lateral ventricles representing the body and the frontal horns and trigones resembling the front and rear tires, respectively.

Figure 1

Axial imaging (T1 and T2 sequences) of the ventricles resembling a Formula One racing car when viewed from above. The large cyst seen posteriorly is due to the Dandy–Walker malformation

“Moose head appearance” or “Viking helmet sign”: Coronal views [Figure 2] at the level of the frontal horns have this characteristic appearance due to agenesis of corpus callosum and eversion of bilateral cingulate gyri into respective frontal horns. The lower part of the face of the moose is formed by the third ventricle.

Figure 2

Coronal imaging (T2 sequence) showing (A) Viking helmet sign and (B) moose head appearance of the ventricles. There is no corpus callosum, and the cingulate gyri (yellow circles) are everted into the ventricles

Sunray appearance: Sagittal imaging [Figure 3] reveals gyri radiating outward in a radial pattern from the ventricle itself due to absence of the corpus callosum and everted cingulate gyrus.

Figure 3

Sagittal imaging (T2 sequence) showing radial arrangement of gyri (green darts) that appear to originate from the ventricle itself in absence of the corpus callosum and everted cingulate gyri

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