Case report: maxillary bone cyst in three horses: diagnosis and treatment using intralesional formalin injection

Introduction

Cystic lesions occurring in the equine skull mainly include paranasal sinus and maxillary cysts. Due to their location and the expansive character of these lesions, surgical treatment by excision is often recommended^1,2,3,4,5,6.

Aim of the study

To describe a minimally invasive technique to treat maxillary bone cysts where conventional surgical treatment could not be performed.

Materials and methods

Three horses presented with unilateral progressive swelling of the maxilla at the department of Surgery and Anesthesiology of Large Animals at Ghent University. Other clinical signs were nasal airway obstruction and weight loss.
 

Oral examination showed bulging of the hard palate in 2 cases. Diagnosis of a maxillary bone cyst was based on radiography, computed tomography (cases 1 and 2) and histopathological examination. As complete surgical excision was not possible because of the anatomical location and the extensiveness of the lesions, the cysts were infused with a 4% formalin solution to chemically debride the cystic lining. Additional treatments included partial curettage (case 1), cyst drainage (all), and tooth extraction (cases 2 and 3). Results and Conclusions: Follow-up was available for 4 to 18 months. The external swelling decreased substantially in size in two cases (Fig. 1 and 2). These horses returned to their previous level of activity without any further complaints. In a 3rd case, the swelling remained stable for 3 months after which it increased again. Owners declined further treatment. Conservative management of bone cysts using formalin proved to be successful in 2/3 cases.

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