Intracranial inflammatory polyp with cerebellopontine compression and leptomeningitis secondary to chronic otitis in a red kangaroo

Abstract

CNS lesions associated with chronic otitis have not been reported in red kangaroos (Macropus rufus), to our knowledge. Here we describe an intracranial inflammatory polyp secondary to chronic otitis in a 6-y-old female red kangaroo with right auricular discharge, loss of balance, and head tilt. Autopsy highlighted a pale-yellow, firm, intracranial polypoid growth that extended from the right tympanic cavity through the internal acoustic meatus and intracranially, with compression of the right cerebellopontine angle. Anaerobic bacterial culture yielded Bacteroides pyogenes from fresh brain and a right external ear swab. Histologically, the tympanic cavity was effaced by neutrophils and macrophages surrounded by lymphocytes and plasma cells, as well as edematous fibrovascular tissue. The epithelial lining of the mucoperiosteum was hyperplastic, with epithelial pseudoglands surrounded by fibrovascular tissue. Areas of temporal bone lysis and remodeling were associated with the inflammatory changes, which occasionally surrounded adjacent nerves. Fibrovascular tissue and inflammatory cells extended from the tympanic cavity through the internal acoustic meatus and into the intracranial cavity, forming the polypoid growth observed grossly; the polyp consisted of a dense core of fibrovascular tissue with scattered clusters of neutrophils and foamy macrophages. Lymphocytes and plasma cells surrounded the leptomeningeal perivascular spaces in the brainstem, cerebellum, and occipital lobe.

Keywords: chronic otitis; macropod; neurologic disease; pathology; red kangaroos.

Figure 1.

Intracranial inflammatory polyp with cerebellopontine compression secondary to chronic otitis in a kangaroo. A pale-yellow, firm, inflammatory polyp (asterisk) extends from the right tympanic cavity through the internal acoustic meatus (arrow) and onto the right occipital bone. Circle = left internal acoustic meatus. Cords of thick, tortuous blood vessels cover the dura mater along the right side of the cranial vault (arrowhead).

Figures 2–7.

Intracranial inflammatory polyp with cerebellopontine compression secondary to chronic otitis in a kangaroo. Figure 2. The right tympanic cavity is filled by inflammatory cells admixed with keratin flakes (asterisks) embedded in abundant edematous fibrovascular tissue that expands the auricular mucoperiosteum. H&E. Figure 3. The epithelial lining of the mucoperiosteum is hyperplastic (arrows) and forms epithelial pseudoglands (arrowheads) within the fibrovascular tissue. H&E. Figure 4. Layers of fibrovascular tissue and inflammatory cells extend from the middle ear mucoperiosteum (asterisk) along the internal acoustic meatus (arrow) before entering the skull base. H&E. Figure 5. The inflammatory polyp (arrow) extends into the cranial cavity over the right occipital bone (asterisk). H&E. Figure 6. The polyp consists of a dense core of fibrovascular tissue (asterisk) with clusters of neutrophils and foamy macrophages (left). H&E. Figure 7. A moderate number of lymphocytes and plasma cells expand the occipital lobe perivascular leptomeningeal spaces. H&E.