Fig. 1

a Computed tomography images obtained to evaluate a head injury 2 years prior to admission, which did not indicate any apparent intracranial abnormality. b–d Contrast-enhanced T1-weighted image (WI) on admission indicating the dilatation of bilateral, third and fourth ventricles. e–f Contrast-enhanced T1-WI (E axial, F sagittal) indicating no obstructive lesions such as a brain tumor or cerebellar anomaly