Patients suspected of harboring a dorsally exophytic tumor should undergo MRI studies of the brain with and without intravenous gadolinium to differentiate this type of tumor from tumors of the fourth ventricle such as PNETs or ependymomas.
- Limited use: As with imaging of the posterior fossa in general, CT scan is of limited versatility as artifact from bony anatomy greatly limits resolution of soft tissue structures. While not ideal, it can suggest a tumor if the fourth ventricle is full.
- Ideal for imaging dorsally exophytic tumors: MRI is the ideal imaging study as it can be obtained in multiple planes. The sagittal plane is generally the most useful for planning.
- Tumor grows into fourth ventricle: The tumor typically arises from the dorsal surface and grows posteriorly into the fourth ventricle.