- A large well-defined irregular shaped mass centered in the fourth ventricle causing downward displacement of the cerebellar tonsils beneath the foramen magnum into the cervical spinal canal.
- It is isointense to the cerebellum on T1-weighted images, hyperintense on T2 and FLAIR, Postcontrast images demonstrate vivid heterogeneous contrast enhancement.
- Dilated supratentorial ventricular system.