Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

Chapter Five The Skull 635
Nasopharyngeal Polyp. In young cats an inflammatory polyp may develop in the middle
ear and extend into the pharynx through the eustachian tube (Fig. 5-29). 67,76-81 This usually
produces increased density and thickening of the osseous bulla. A soft-tissue mass may
infrequently be identified within the nasopharynx. The clinical signs usually are related to
upper respiratory obstruction, and the mass usually is visible within the external ear canal
or nasopharynx. A similar condition has been reported in a dog. 82
Hydrocephalus. In severe hydrocephalus there may be a smooth, homogenous appearance
to the calvarium as a result of the flattening of the juga and thinning of the calvarial
bones. 45,83,84 The shape of the skull may be markedly domed, and the frontal bones may
bulge cranially. An open fontanelle or open sutures may be noted (Fig. 5-30). In adultonset
hydrocephalus, which occurs after the skull is well ossified, bony changes usually are
not visible. To confirm the diagnosis of hydrocephalus when bony changes are absent, ventriculography,
CT, ultrasonography, or MRI may be needed.
Ultrasonography can be used to confirm the diagnosis of hydrocephalus and is performed
easily if an open fontanelle is present. 85 The ventricles can be identified and their
size evaluated. Although there is some variation by breed in normal maximal ventricle
size, it should not exceed 0.35 cm or 14% of the ventrodorsal dimension of the
brain. 36,38,39,85,86 Measurements between 0.15 cm and 0.35 cm are suggestive of hydrocephalus.
37 The ventricles are easily identified in both transverse and longitudinal planes.
They appear as anechoic crescent-shaped structures (Figs. 5-31 to 5-33). In severe hydrocephalus
the third and fourth ventricles can be identified as an oval or linear anechoic
structure located on the ventral midline. When the fontanelle is large, the examination is
Fig. 5-29 A 3-year-old female domestic short-haired cat
with a head tilt. A, The left lateral oblique view revealed a
normal right osseous bulla that contained air. A prominent
soft-tissue mass was noted in the pharynx (white arrows).
B, The right lateral oblique view revealed a slightly thickened
irregular left osseous bulla (white arrow) that contained tissue
density. Diagnosis: Auralpharyngeal polyp.
A
B