Page 196 - Atlas of Small Animal CT and MRI

186 Atlas of Small Animal CT and MRI

include multifocal T2* susceptibility effects from lacunar Degenerative disorders
infarction (Figure 2.5.8). 46
Age‐related degeneration
Exogenous toxins Gross changes in the brain that occur from age‐related
Neurotoxicity can occur from consumption of recog- degeneration include cortical and hippocampal atrophy
nized toxins or from adverse effects of pharmaceuti- and ventricular enlargement. 52–55 The frontal lobes are
cals. The list of neurotoxins that affect the brain is particularly vulnerable, decreasing in volume dispro-
extensive, and many do not produce pathology portionately more than other parts of the cerebrum. 54,55
detectable with neuroimaging techniques. Clinically, Underlying pathology includes neuronal loss due to
exposure to a neurotoxin may not be recognized; accumulation of toxic proteins, oxidative damage, and
53
therefore, diagnoses are often speculative and rarely cerebrovascular pathology. CT and MR features include
confirmed. Comprehensive coverage of neurotoxicity enlargement of the ventricular system and prominence
is beyond the scope of this text, but we will highlight of the brain cortical margins and sulci on T1 and T2
one representative example. images due to expansion of subarachnoid space volume
(Figure 2.5.10). 56
Metronidazole toxicity
Metronidazole has been documented to induce neuro- Other degenerative disorders
toxicity in both dogs and cats. 47–49 Although clinical Neurodegenerative disorders of the brain often have
signs in the dog are referable primarily to the cerebellum, a known underlying cause, such as an inborn error
neurologic signs in the cat seem to be less specific. 47–49 of metabolism (lysosomal storage disorders) or an
MR imaging features of metronidazole toxicity in people acquired metabolic, inflammatory, or toxic source, and
include focal T2 and FLAIR hyperintensity, primarily in the degenerative pathology represents an end stage of
the dentate and other cerebellar nuclei, although similar disease. Although each neurodegenerative disorder has
lesions have been described in other regions of the specific pathologic characteristics, common features
brain. Lesions do not contrast enhance and resolve after include neuronal loss with associated volume reduction,
discontinuation of the drug. 50,51 Although imaging demyelination, and cavitation from tissue necrosis.
findings of metronidazole toxicity have not been well Examples of reported neurodegenerative disorders in
described for dogs or cats, our limited experience dogs and cats include neuroaxonal dystrophy, 57–59
suggests MR features are similar to those in people leukoencephalomyelopathy, 60–65 and Alaskan Husky
(Figure 2.5.9). encephalopathy 66–68 (Figure 2.5.11).

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