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Chapter 4: Advanced Imaging: Intracranial Surgery 41

A B

C D

Figure 4.14 Transverse T2‐weighted (A), T2* GRE (B), T1‐weighted (C), and T1‐weighted postcontrast (D) MRI of a 12‐year‐old English Springer Spaniel
presented with acute‐onset progressive obtundation. The mass is complex with fluid–fluid levels (arrow in A) and evidence of hemorrhage (susceptibility
artifact on the T2* GRE images and high signal on the T1W images). The complex nature of the mass, lack of distinct rim, extensive perilesional edema, and
enhancement (arrows in D) of the solid components of the mass are suggestive of a hemorrhagic neoplasm rather than benign hematoma.

Territorial infarcts occur with large artery disease and result in DWI is useful in determining the age of the infarct, with acute
large rectangular/wedge‐shaped lesions. They are most commonly (<9 days old) infarcts appearing hyperintense on DWI and
seen in the cerebellum (small breeds, with Cavalier King Charles hypointense on the apparent diffusion coefficient (ADC)
Spaniels being predisposed) [109]. Large territorial infarcts in the map [110–113]. After 7–9 days the DWI pseudonormalizes.
vascular territory of the middle or rostral cerebral arteries are occa- DWI may be helpful in giving some prognostic information if
sionally seen in sight‐hounds among other breeds. there are multiple infarcts by showing if they are occurring at dif-
Lacunar infarcts are small infarcts affecting end arteries within ferent time periods. MRI and CT angiography of intracranial
deep gray matter structures (e.g., thalamus and caudate nucleus) arteries is usually of limited or no value for the diagnosis of
(Figure 4.17) [108]. They are most commonly seen in larger dogs canine and feline brain infarcts due to the small size of the blood
and may be multiple. Chronic lacunar infarcts are sometimes seen vessels affected, which are often not visible even in normal ani-
as an incidental finding. mals [48,114]. However, recent work has suggested that MRS