Aetiopathogenesis and surgical therapy of heterotopic polyodontia and aural fistula in horses

Abstract

Aetiopathogenesis and surgical therapy of heterotopic polyodontia and aural fistula in horses 14 horses of different breeds with an average age of three years were referred with the clinical signs of an auricular fistula or a swollen base of the ear. Diagnostic procedures included clinical examination with insertion of a probe into the sinus tract. Digital radiographic examination including contrast fistulography or with a metal probe within the tract was performed with lateral and oblique projections. Computed tomography of the head was added in seven of the 14 horses. In 12 horses, an aural fistula with mucous exudation was present close to the ear respectively at the margin of the ear cartilage. A swelling close to the base of the ear was present in another two horses. In ten of the 14 horses a heterotopic polyodontia could be detected radiographically with dense structures close to the temporal bone or multiple teeth like structures with enamel folds. A definite determination of the number and localization of teeth and furthermore detection of secondary lesions of surrounding bone and neurologic tissue due to compression could only be obtained with computed tomography. Following diagnostic procedures, surgical treatment was performed in 13 of the horses with complete removal of the sinus formation and heterotopic teeth. One horse did not receive surgical treatment due to the decision of the owner and to a poor prognosis for a surgical benefit. No intra-and postoperative complications could be observed except in one horse with a temporary unilateral ptosis. Functional and cosmetic results were considered to be good. It was a remarkable fact that all horses with a diagnosis of heterotopic polyodontia in this study were mares. In the majority of cases, heterotopic polyodontia was associated with the clinical presence of an aural fistula. Reversely, the primary etiology of an aural fistula was not a heterotopic polyodontia in any case, since a dermoid cyst was diagnosed in four of the horses. Despite the good surgical results in this study, surgical therapy of an auricular fistula with or without heterotopic polyodontia remains a serious procedure with the risk of complications due to the complex anatomy of the area.Keywords: Horse / head / aural fistula / heterotopic polyodontia / temporal odontma / dentigerous cyst / ear tooth / dermoid cyst / radiology / computed tomography Ursachen und chirurgische Therapie der heterotopen Polyodontie und der Ohrgrundfistel beim Pferd Einleitung

Dentigerous cysts with exostosis of the temporal bone in horses – A new variant diagnosed by computed tomography

“…Some authors differentiate between two types of ‘temporal teratoma’: the dermoid type without associated dental structures and the dentigerous type that contains tooth‐like structures (Mason, 1974; Misdorp, 2003). The latter is more common, particularly in younger horses (Bartmann & Bienert‐Zeit, 2012; Mason, 1974). Nevertheless, most authors use ‘dentigerous cyst’ for cystic lesions within the temporal region that mostly (but not always) contain dental structures (Barakzai & Dixon, 2012; Easley et al., 2010; Gaughan, 2010; Smith et al., 2012).…”

“…In some cases, radiographs were sufficient for diagnosis (Easley et al., 2010), especially when oblique projections are used (Ebling et al., 2009) or contrast medium was injected into the draining tract (Gaughan, 2010). Other authors recommend a CT examination as the diagnostic modality of choice (Barakzai & Dixon, 2012; Bartmann & Bienert‐Zeit, 2012; Smith et al., 2012) because smaller dental structures may be missed on radiographs (Dicht et al., 2011). In the two cases presented here, CT in combination with positive contrast sinography was the superior imaging modality to identify the dentigerous cyst with exostosis and for surgical planning.…”

“…Surgical removal is commonly recommended (Bartmann & Bienert‐Zeit, 2012; Easley et al., 2010; McIlwraith et al., 1998; Rashmir‐Raven et al., 1990; Tremaine, 2011), even if the procedure is just for cosmetic reasons or to prevent infection, as the cysts are usually not painful (Gaughan, 2010). Perioperative antibiotics and NSAIDs are recommended for controlling bacterial infections and inflammatory response following surgery (Gaughan, 2010).…”