Case of the month: 2-year-old mixed-breed dog shows pain at the opening of the mouth and his right ear canal ends blind
Signalment and anamnesis
- Dog, mixbreed, 2 years, male intact, weighing 20 kg
- Shows pain at the opening of the mouth and has a reduced appetite
- The right ear canal is not fully visible and ends blind
- There is also pain on palpation causal to the angle of the jaw
CT description
- The right external auditory canal, the tympanic cavity and the inner ear are severely deformed
- The medial portion of the right horizontal external auditory canal and the tympanic cavity are filled completely with hypoattenuating fluid
- The right tympanic cavity is dilated and shows surrounding mixed osteolysis, osteoproliferation and osteosclerosis
- The pars petrosa of the temporal bone with the inner ear also shows osteoproliferative bone remodeling
- The medial part of the horizontal auditory canal is luminal narrowed and shows wall mineralization
- In the post-contrast series, the wall is also thickened and shows increased contrast enhancement
- Between the medial and lateral part of the external auditory canal a soft tissue dense membrane is visible, which completely separates both compartments
- The lateral portion is gas-filled, while the medial portion is fluid-filled
- Starting from the ventral part of the fluid-filled right horizontal auditory canal, a fluid-filled fistula canal is visible, which can be traced rostroventrally along the pterygoid and masseter muscles up to the level of the soft palate
- The adjacent musculature shows clear contrast enhancement (myositis)
- The right parotid (6 mm), submandibular (8 mm) and right medial retropharyngeal lymph nodes (12 mm) are moderately enlarged
- The contralateral left external auditory canal is unremarkable
Diagnosis
- With regard to the separation of the medial and lateral parts of the right external auditory canal, a congenital atresia of the right external auditory canal can be assumed
- Secondary right-sided chronic otitis externa, media and interna with concomitant osteolysis of the tympanic cavity, the inner ear and concomitant fistula formation with masticatory muscle myositis
- Reactive parotid, submandibular and medial retropharyngeal lymphadenopathy
Outcome
The patient was treated surgically
Discussion
Atresia of the external auditory canal (EACA) is a rare anomaly that can be congenital or traumatic. In dogs, EACA is treated surgically, either by the Lacroix technique or by total ear canal ablation and bulla osteotomy (TECALBO).
Literature:
Schmidt, K., Piaia, T., Bertolini, G. and De Lorenzi, D. (2007), External auditory canal atresia of probable congenital origin in a dog. Journal of Small Animal Practice, 48: 233-236. doi.org/10.1111/j.1748-5827.2006.00241.x
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Many thanks to Dr. DECVDI Thorsten Rick for this interesting case report
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