MR Imaging Characteristics of Wingless-Type–Subgroup Pediatric Medulloblastoma

Pre- and postoperative sagittal T1-weighted and transverse T2-weighted images of a midline-extraventricular (subtype B) WNT-subgroup medulloblastoma. The preoperative sagittal T1-weighted image (A) shows a low-lying tumor in the posterior fossa, which is centered on the cisterna magna and pushing the vermis cranially, with extension to the foramen of Magendie but only minimal extension into the fourth ventricle. In transverse T2WI (B–D), no definite laterality is seen; hence, the tumor appears to be gross midline, but there is some involvement of the left foramen of Luschka (LS-1c = L1) and left inferomedial cerebellum (LS-2c = L1). The combined preoperative laterality score is ambiguous (LS-3c = L2). One of the PICAs (probably the left) is running over the upper aspect of the tumor, indicating displacement from below (D). Postoperative images (E–H) show a relatively spared vermis and more pronounced abnormalities on the left side, which include damage to the left dentate nucleus and the left inferomedial cerebellum (LS-4c = L2) and a left PICA territory infarction. The combined pre- and postoperative laterality score suggests a left-sided tumor origin (LS-5c = L4).

Pre- and postoperative transverse T2WI of an off-midline–intraventricular (subtype C) WNT-subgroup medulloblastoma. A right-sided predominance is evident in the preoperative images, but the tumor has a substantial intraventricular component (A–D). This pattern is highlighted by the involvement of the right foramen of Luschka (LS-1c = R1) and by invasion of the right dentate nucleus and right superior cerebellar peduncle (LS-2c = R2). Preoperative imaging data suggest that overall, this tumor is off-midline, with a right-sided predominance (LS-3c = R3). The postoperative damage pattern is identical, with lesions in the right dentate nucleus and superior cerebellar peduncle (LS-4c = R2) and a right PICA territory infarction (E–H). The aggregate laterality score indicates a clear right-sided laterality (LS-5c = R5).

Pre- and postoperative transverse T2WI of an off-midline–extraventricular (subtype D) WNT-subgroup medulloblastoma. This tumor is centered on the right cerebellopontine angle cistern and involves the right foramen of Luschka (B–C), with no extension to the fourth ventricle (LS-1c = R2). Invasion of the right lateral brain stem and right inferomedial cerebellum is also suggested (LS-2c = R2). Accordingly, preoperative anatomic imaging data indicate a definite laterality (LS-3c = R4). In postoperative images, damage is seen within the right lower brain stem (F), right inferomedial cerebellum (F–G), and right middle cerebellar peduncle (H) (LS-4c = R3), with no damage to juxtaventricular structures (dentate nucleus, superior cerebellar peduncle). The aggregate laterality score indicates right-sided laterality (LS-5c = R7).