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Figure 4.3 (A) Sagittal plane ultrasound of the brain of a 5‐month‐old Chihuahua presented with episodic depression and progressive ataxia. Transcranial
ultrasound is easily performed in young or small animals if the fontanelle is open, as in this case. Due to high contrast between soft tissue and fluid it is easy to
assess the ventricular system within the brain provided a suitable acoustic window is available. The ultrasound study in this case allowed clear visualization of
the entire ventricular system and confirmed the presence of hydrocephalus. (B) Transverse plane CT of the same dog showing moderately severe hydrocephalus
and open fontanelles (arrow). In this case the hydrocephalus was possibly an incidental finding as the dog also had atlanto‐axial subluxation.
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Figure 4.4 (A) Dorsal plane T2‐weighted MRI of a 10‐year‐old Fox Terrier presented with progressive hemiparesis. The image shows a large intradural–
extramedullary mass (arrow) at C1–2 and presumed to represent a malignant peripheral nerve tumour. (B, C) Ultrasound images of the left side of C1 and
C2 clearly show the mass as an irregular hypoechoic mass (arrows) extending through the intervertebral foramen and into the vertebral canal. It was possible
to perform ultrasound‐guided fine‐needle aspiration of the mass.
