Page 92 - Feline diagnostic imaging

6.3 ­iseases oo the Feline SSine 89

(a) (b) (c)

(d) (e)

Figure 6.13 MR appearance of toxoplasma meningoencephalitis in an 11-year-old domestic shorhair presenting with left facial
paresis and vestibular signs. (a) Transverse T2W, (b) transverse FLAIR, (c) transverse precontrast T1W, (d) transverse postcontrast T1W,
(e) sagittal postcontrast T1W images. A unilateral ill-defined lesion is seen in the brainstem, characterized by a central hypointense
area and diffuse surrounding hyperintensity (arrows). The central portion of the lesion is moderately contrast enhancing (arrowheads),
whereas the surrounding tissue does not enhance, consistent with perilesional edema. A central area of necrotic tissue with
intralesional protozoa was identified postmortem. Source: Images courtesy of Dr Kathryn Phillips, UC Davis.

lymphoma can produce ischemic lesions on MRI. Cats head trauma, which in cats are most commonly hit‐by‐car
have also had reported intracranial changes detectable or crush injuries (Figure 6.19). CT may be of greater benefit
with MRI related to hypertension; these have been charac- to more critical patients, since it is fast and can be per-
terized as bilateral hyperintense areas in the cerebral white formed without general anesthesia [60]. A full‐body CT will
matter on T2 and FLAIR images [58]. likely become a first‐line diagnostic in trauma cases in vet-
The brain is a highly metabolically active organ and as erinary medicine as it has in human medicine. In contrast,
such metabolic disturbances can produce neurologic signs. MRI can provide prognostic information on brain tissue
It is important to recognize the features of metabolic integrity and hemorrhage, and evaluate the relationship of
encephalopathies, so that treatment options are considered calvarial fractures to the potential for clinically significant
appropriately. Generally, these will manifest as bilaterally traumatic brain injury [61].
symmetric lesions that are hyperintense on T2W images
and do not contrast enhance. Thiamine deficiency in cats
(Figure 6.18) is a good example of a relatively specific MR 6.3 Diseases of the Feline Spine
appearance that has been shown to resolve in MR images
with appropriate treatment [59]. 6.3.1 Neoplasia
Head trauma represents a diagnostic imaging challenge
for clinicians. Radiographs are suboptimal in providing the In feline patients presenting with spinal neurologic signs,
needed information to direct treatment of traumatic brain neoplasia is a primary clinical concern, which is in part due to
injuries. They can, however, be used to better document its prevalence relative to the more common and more “benign”
whole‐body trauma. MRI and CT are both used to evaluate disease processes affecting the canine spine, like intervertebral