Findings
There is a heterogeneously enhancing mass centered within the fourth ventricle, without significant internal restricted diffusion, extending inferiorly into the upper cervical spinal canal to the level of C2 and through the right greater than left foramina of Luschka, measuring approximately 3.3 x 3.1 x 6.7 cm (AP by TV by CC), exhibiting regional mass effect, pushing the pons, medulla, and overall brainstem anteriorly, and producing moderate dilatation of the fourth ventricle superior to the mass, third ventricle, and bilateral lateral ventricles. There is nonenhancing FLAIR hyperintense signal along the anterior and left lateral ependymal lining of the fourth ventricle with T2/FLAIR hyperintense signal extending towards the left middle cerebellar peduncle. No other sites of abnormal enhancement are noted. The major intracranial flow voids are intact.
There is no midline shift. There are no intra-axial or extra-axial collections. There is no acute intracranial hemorrhage or restricted diffusion to suggest acute territorial infarction.
There are retention cysts versus polyps in the bilateral maxillary sinuses and left frontal sinus. The mastoid air cells are well-aerated. The visualized orbital structures are normal.
Impressions
6.7 cm heterogeneously enhancing mass centered within the fourth ventricle extending into the upper cervical spinal canal at the level of C2 and through the bilateral foramina of Luschka, and producing moderate dilatation of the fourth ventricle superior to the mass, third ventricle, and bilateral lateral ventricles. The imaging characteristics of this mass are most consistent with an ependymoma. Consider MR imaging of the entire spinal axis for evaluation of drop metastases.