Bilateral tympanokeratomas (cholesteatomas) with bilateral otitis media, unilateral otitis interna and acoustic neuritis in a dog

23 de dezembro de 2020

Timpanoqueratomas bilaterais (colesteatomas) com otite média bilateral, otite interna unilateral e neurite acústica em um cachorro

Liv Østevik1, Kathrine Rudlang, Tuva Holt Jahr, Mette Valheim and Bradley Lyndon Njaa

Background: An aural cholesteatoma, more appropriately named tympanokeratoma, is an epidermoid cyst of the
middle ear described in several species, including dogs, humans and Mongolian gerbils. The cyst lining consists of
stratifed, keratinizing squamous epithelium with central accumulation of a keratin debris. This case report describes
vestibular ganglioneuritis and perineuritis in a dog with chronic otitis, bilateral tympanokeratomas and presumed
extension of otic infection to the central nervous system.
Case presentation: An 11-year-old intact male Dalmatian dog with chronic bilateral otitis externa and sudden
development of symptoms of vestibular disease was examined. Due to the dog’s old age the owner opted for euthanasia without any further examination or treatment and the dog was submitted for necropsy. Transection of the ears
revealed grey soft material in the external ear canals and pearly white, dry material consistent with keratin in the tympanic bullae bilaterally. The brain and meninges were grossly unremarkable. Microscopical fndings included bilateral
otitis externa and media, unilateral otitis interna, ganglioneuritis and perineuritis of the spiral ganglion of the vestibulocochlear nerve and multifocal to coalescing, purulent meningitis. A keratinizing squamous epithelial layer continuous with the external acoustic meatus lined the middle ear compartments, consistent with bilateral tympanokeratomas. Focal bony erosion of the petrous portion of the temporal bone and squamous epithelium and Gram-positive
bacterial cocci were evident in the left cochlea. The fndings suggest that meningitis developed secondary to erosion
of the temporal bone and ganglioneuritis and/or perineuritis of the vestibulocochlear nerve.
Conclusions: Middle ear tympanokeratoma is an important and potentially life-threatening otic condition in the
dog. Once a tympanokeratoma has developed expansion of the cyst can lead to erosion of bone and extension of
otic infection to the inner ear, vestibulocochlear ganglion and nerve potentially leading to bacterial infection of the
central nervous system.
Keywords: Cholesteatoma, Dog, Ear, Meningitis, Otitis interna, Tympanokeratoma

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