Page 180 - Atlas of Small Animal CT and MRI

Figure 2.3.7 Arachnoid Cyst (Canine) CT

(a) CT, TP (b) CT, TP (c) CT, TP

(d) CT, SP
2y FS Maltese with unlocalized pain without neurologic deficits. Images a–c are representative transverse images of the brain at the level
of the parietal lobes (a), occipital lobes (b), and cerebellum (c). Moderate, symmetrical lateral ventriculomegaly is present (a). A large,
fluid‐attenuating arachnoid cyst (b–d: asterisk) arises from the quadrigeminal cistern and is bounded ventrally by the tectum
(d: large arrow) and cerebellum (d: arrowhead), rostrally by the corpus callosum (d: small arrow), and dorsally by the tentorium cerebelli
(not seen). The cyst is predominantly subtentorial, and it displaces and compresses the cerebellum ventrally.

Figure 2.3.8 Arachnoid Cyst (Canine) MR
3y MC Shih Tzu with tetraparesis. The MR
examination was performed to fully evaluate
a diagnosed occipitoatlantoaxial malforma-
tion. Transverse images (a,c) are at the same
level at the occipital lobes. A well‐defined
arachnoid cyst with pure‐water signal charac-
teristics arises from the quadrigeminal cistern
(a,b: asterisk) and is bounded ventrally by the
tectum (d: large arrow) and cerebellum
(d: arrowhead), and rostrally by the corpus
callosum (d: small arrow). Focal spinal cord
(a) T1, TP (b) T1, SP
narrowing and parenchymal T2 hyperinten-
sity are also evident on image d, associated
with the occipitoatlantoaxial malformation.

(c) T2, TP (d) T2, SP

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