T1 sagittal pre gad T1 axial post gad T1 coronal post gad

Diagnosis: High grade vermian astrocytoma

Metastasis is the most common intraaxial posterior fossa tumor in adults. 80% of parenchymal CNS metastases are multiple. Astrocytoma in this age group and location is less common. Medulloblastoma is not in the differential since it is a tumor of much younger patients. Also, they tend to have a more homogeneous enhancement pattern. Ependymoma and choroid plexus papilloma are intraventricular lesions and may enhance like this but are not considerations since this tumor is intraaxial and effaces the fourth ventricle due to external mass effect rather than from being within the ventricle. Related Cases

Pontine Astrocytoma Choroid Plexus Papilloma Vermian Astrocytoma