Astrocytomas and oligodendrogliomas represent one third of histologically confirmed
canine brain tumors. Our purpose was to describe the magnetic resonance (MR)
imaging features of histologically confirmed canine intracranial astrocytomas and
oligodendrogliomas and to examine for MR features that differentiate these tumor types.
Thirty animals with confirmed astrocytoma (14) or oligodendroglioma (16) were studied.
All oligodendrogliomas and 12 astrocytomas were located in the cerebrum or thalamus,
with the remainder of astrocytomas in the cerebellum or caudal brainstem. Most (27/30)
tumors were associated with both grey and white matter. The signal characteristics of
both tumor types were hypointense on T1-W (12 each) and hyperintense on T2-W (11/14 astrocytomas, 12/16 oligodendrogliomas). For astrocytomas and
oligodendrogliomas, respectively, common findings were contrast enhancement (10/13,
11/15), ring-like contrast enhancement (6/10, 9/11), cystic regions within the mass
(7/14, 12/16), and hemorrhage (4/14, 6/16). Oligodendrogliomas were significantly more
likely to contact the brain surface (meninges) than astrocytomas (14/16, 7/14,
respectively, P = 0.046). Contact with the lateral ventricle was the most common finding,
occurring in 13/14 astrocytomas and 14/16 oligodendrogliomas. No MR features were
identified that reliably distinguished between these two tumor types. Contrast
enhancement was more common in high grade tumors (III or IV) than low grade tumors
(II, P = 0.008).