Case of the Week

CT head without contrast (A) is negative for acute intracranial pathology but shows dilated occipital horns of both lateral ventricles in a colpocephaly-like fashion. Axial FLAIR sequence (B) shows a right frontal and insular infarct (blue arrow) along with a V-shaped anterior corpus callosum (red arrows). Lateral internal carotid artery digital subtraction angiography (C) fails to visualize a distinct arterial occlusion but shows a dilated proximal internal carotid artery (red arrow) and an abnormally straight course of the intracranial arteries (blue arrows) with absent basal collaterals. Coronal T2-weighted MRI (D) shows a V-shaped corpus callosum (green arrow) and a deficient anterior cingulate gyrus (red arrow). Sagittal T1-weighted MRI (E) shows inferior bending and hypoplasia of the anterior corpus callosum (blue arrow), along with atypical radial gyration of the frontal lobe (red arrows) with apparent absence of the anterior cingulate gyrus (green arrow). Axial T2-weighted MRI (F) shows flattening of the pons with impression of the basilar artery (red arrow), also known as the "twin peaks" pons (yellow arrows).