Ear-base Swellings in Horses: CT-Guided Surgery Cures Dentigerous Cysts (7-Case Series)

Dentigerous cysts in horses: A retrospective study

M. Schläpfer; B. Donati; A. E. Fürst; M. A. Jackson

Background

Dentigerous cysts are congenital lesions in horses, classically at the base of the ear but also reported in paranasal sinuses and jaws. Recent literature proposes a third variant featuring an exostosis of the temporal bone without ectopic dental tissue. With broader access to CT, characterization and surgical planning have improved. This study describes imaging features (radiography vs CT), occurrence of temporal exostosis, treatment, and outcomes in affected horses.

Methods

Medical records from a university equine hospital (2007–2023) were reviewed for confirmed dentigerous cysts. Seven horses (ages 2–12 years) were included. Data extracted comprised signalment, clinical signs, imaging (radiography in 5/7; CT in 6/7; fistulography in 2; ultrasonography in 1; nasal endoscopy in 1), surgical approach (standing or under general anaesthesia), and histopathology when available (3 cases).

Results

Lesions were most often at the ear base; one case involved the maxillary sinus. Four of seven horses were Icelandic. Presenting signs included peri-aural swelling and/or a draining tract; one horse had isolated unilateral nasal discharge. CT outperformed radiography in defining lesion extent, identifying dental material and temporal exostosis, and informing surgical planning, including one case with slight intracranial protrusion of an ectopic tooth. Two cases resembled the recently described “temporal dentigerous cyst with exostosis” variant lacking dental tissue; in both, the tract was closely related to the bony change. All horses underwent surgery (standing in one minor case); complete excision of the tract with removal of dental tissue and, when indicated, exostosis was achieved. Wounds healed uneventfully with no recurrence; transient postoperative ear mobility deficit resolved in one case.

Limitations

This is a small, single-centre retrospective series of a rare condition. Breed overrepresentation (Icelandic horses) may reflect referral bias and requires confirmation. Histopathology was performed in only a subset, and imaging protocols varied.

Conclusions

Dentigerous cysts typically occur near the ear base but can present in atypical sites such as the maxillary sinus. CT is the modality of choice for precise localization, detection of dental tissue or temporal exostosis, and risk-aware surgical planning. Surgical excision yields excellent outcomes; when a draining tract is intimately associated with an exostosis, removing both structures appears prudent to prevent recurrence. The apparent cluster in Icelandic horses merits further study.

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