Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

636 Small Animal Radiolo g y and Ultrasono graphy
easy. No correlation between fontanelle size and degree of hydrocephalus has been determined.
There is no correlation between ventricle size and severity of clinical signs. In most
instances, the cause of the ventricular enlargement cannot be determined by ultrasonographic
examination. 36 Although the brain can be examined through a craniotomy, this is
not recommended because the diagnosis can be made using CT or MRI, which are noninvasive
techniques.
Lissencephaly. Lissencephaly, a rare congenital brain disorder in which the brain does not
have normal convolutions (sulci and gyri), may be detected radiographically because the
calvarium lacks the normal convolutional markings. This condition produces a radiographic
appearance similar to that of hydrocephalus.
Fig. 5-30 A 3-month-old female
Poodle with depression, lateral strabismus,
and occasional seizures. A,
The lateral radiograph revealed a
large bony defect (open white arrow)
dorsally (a large open fontanelle),
marked doming of the skull, and a
near-homogeneous density over the
skull indicating obliteration of the
normal juga. B, The ventrodorsal
view revealed open cranial sutures
(white arrows) and thinning of the
calvarium. Diagnosis: Severe hydrocephalus.
A
B
Fig. 5-31 Transverse sonograms of
the brain of a 5-month-old male
Chihuahua with a history of vomiting
and diarrhea of 1 week duration.
The lateral ventricles are mildly
dilated. This represents mild hydrocephalus,
which is not unusual in a
dog of this breed. Diagnosis: Mild
hydrocephalus.