Fig. 7

A A 15-year-old girl presented with nausea and vomiting. Brain CT scan without contrast administration in axial (a), sagittal (b), and coronal (c) reformats. A well-defined heterogeneous mass was observed centered in the foramen magnum with a marginal extension on the right side (asterisks). It shows homogenous density and extends below the foramen magnum caudally (arrows). It induces a mass effect on the inferior aspect of the cerebellar hemisphere and medulla oblongata, resulting in obstructive hydrocephalus. CT computed tomography. B Brain MRI without and with intravenous contrast medium. The figure indicates a lobulated, heterogeneous, solid mass, centered within the foramen magnum (asterisks). This lesion shows mixed heterogeneous intensity with predominantly iso-to-hypointensity on T1-weighted imaging (a), high signal intensity on T2-weighted imaging (not shown), and heterogeneous enhancement after contrast medium administration (b). Diffusion-weighted images demonstrate restricted diffusion (c, d). It induces a mass effect over the medulla oblongata with resultant hydrocephalus (arrow; a). The findings of neuroaxis imaging were unremarkable (not shown). MRI magnetic resonance imaging. C Proton magnetic resonance spectroscopy analysis (single-voxel technique) for a female pediatric patient presented with nausea and vomiting. There is a high NAA peak, a low choline peak, and choline to creatinine ratio. The taurine peak is not evident at 3.25 or 3.43 ppm. NAA N-acetyl aspartate