Page 53 - Zoo Animal Learning and Training

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Figure 4.21 Transverse T2‐weighted (A) and constructive interference in steady state, or CISS (B) MRI of a 5‐month‐old dog with severe congenital hydro-
cephalus. The cortical thinning and massive dilation of the ventricles and thin dome‐shaped calvarium may be seen in congenital hydrocephalus but are not
seen with acquired hydrocephalus in older dogs. The hydrocephalus was due to stenosis (arrow) of the mesencephalic aqueduct with reduced size and axial
displacement of the caudal colliculi visible on the CISS image.

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Figure 4.22 Sagittal T2‐weighted (A), transverse FLAIR (B), and transverse T1‐weighted postcontrast (C) MRI of a cat with obstructive hydrocephalus due
to feline infectious peritonitis. Note the dilation of all parts of the ventricular system rostral to the foramen magnum, indicating that the obstruction to CSF
flow is likely to be at the lateral apertures of the fourth ventricle or at the foramen magnum. The FLAIR and postcontrast images show abnormal T2 hyper-
intensity and enhancement of the ependyma within the fourth ventricle and irregular enhancement of the choroid plexi commonly seen with FIP. On the
sagittal T2‐weighted images the low signal of the CSF within the mesencephalic aqueduct was due to a flow artifact.