ABSTRACT
Intracranial masses, whether neoplastic or not, can be subdivided based on location into intra-axial and extra-axial. They can be further characterized by number, location, size, margination, signal intensity, homogeneity, contrast enhancement, and concurrent imaging findings. Co-existing intracranial masses of different histogenesis in the same patient are rare but have been reported. This chapter covers possible associated findings with intracranial masses, the accuracy of magnetic resonance imaging (MRI) in the diagnosis of intracranial neoplasia, and MRI findings reported with specific tumor types. A variety of pathologic sequelae can be associated with intracranial masses, including hydrocephalus, cervicothoracic syringomyelia, peritumoral edema, mass effect, and brain herniation. Several tumor types can affect the ventricular system including choroid plexus tumors (papillomas and carcinomas), ependymomas and meningiomas in dogs and cats, and neurocytomas in dogs. Choroid plexus tumors are the most common ventricular tumors in dogs, with choroid plexus carcinomas being more common than choroid plexus papillomas.
