Labyrinthitis Ossificans in a Cynomolgus Macaque (Macaca fascicularis)

Gayathriy Balamayooran, Hannah M. Atkins, Christopher T. Whitlow, Samuel T. Aycock, Michael A. Nader, J. Mark Cline, David L. Caudell

Research output: Contribution to journalArticlepeer-review


Labyrinthitis is inflammation of the membranous and bony labyrinth of the inner ear. Typical portals of entry include hematogenous spread from the cochlear vasculature, passage of otitis media pathogens through the round window, and most commonly, meningogenic spread from the subarachnoid space. The sequela of chronic inner ear inflammation is labyrinthitis ossificans, in which inner ear structures are replaced by fibrous and osseous tissues. Labyrinthitis in humans has been reported concurrently with infection due to various viruses (for example, varicella–zoster, measles, mumps) and bacteria (for example, Treponema pallidum, Streptococcus pneumoniae) and may be associated with vertebrobasilar ischemia and meningitis. Profound sensorineural hearing loss is a common, serious complication of this disease. Here, we report a case of labyrinthitis ossificans in a cynomolgus macaque (Macaca fascicularis) with a potential infectious etiology. Historically, this animal had an indwelling femoral intravenous catheter for more than 4 y. He presented with a right-sided head tilt and incoordination of 2 mo duration. The macaque was treated with NSAID and antibiotics, which corrected the incoordination but not the head tilt. MRI revealed right-sided labyrinthitis, and euthanasia was elected due to clinical signs that were refractory to treatment. Gross pathology was unremarkable, but histopathology revealed chronic labyrinthitis ossificans with local fibroplasia and vestibuloauditory neuritis. We describe here the clinical features, imaging, and histologic lesions of labyrinthitis in a macaque.

Original languageEnglish (US)
Pages (from-to)239-242
Number of pages4
JournalComparative Medicine
Issue number3
StatePublished - Jun 2018

All Science Journal Classification (ASJC) codes

  • General Biochemistry, Genetics and Molecular Biology
  • General Veterinary


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