Today’s case is a 3-year-old Alpaca with a one-year history of otitis media and a head tilt.
Soft tissue pre- and postcontrast (3 mm) and bone (1 mm) images of the brain were acquired. The right side of the patient is on the right side of the screen.
In the first precontrast image, the more normal tympanic bulla on the left contains air and trabecular bone. On the right side the tympanic bulla, petrous temporal bone, and inner ear structures are absent (best seen on image 2). On the precontrast and bone images, there is a lobular, mineralized mass in the cranial vault adjacent to the petrous temporal bone. On postcontrast images (3), the mass enhances mildly on the periphery, and a second mass is visible in the position of the tympanic bulla. In all three images, hypoattenuating areas within the brain near the abnormalities indicate edema.
Moving caudally, the remnant of the right tympanic bulla is sclerotic, as is the stylohyoid bone. This indicates chronic inflammatory disease. A large, hyperattenuating, partially mineralized, extra-axial mass is visible on the precontrast image. On postcontrast images (6), this resolves into two lobular masses. Both are peripherally enhancing, with non-enhancing or enhancing centers.
Images 7 and 8 show the extension of the mass into the region of the cerebellum.
- otitis media and interna with intracranial extension and abscessation
The sclerosis of the involved bones indicate a chronic inflammatory disease. The osseous destruction is severe and could indicate a neoplastic transformation. However, the soft tissue masses were all peripherally enhancing, which is typical of abscessation.
An ultrasound-guided fine needle aspirate of the lesion in the position of the right bulla yielded caseous pu,s which was submitted for culture. Gram positive cocci and rods were seen; however, there was no growth.