Presumed intraosseous abscess of the hard palate in a mare

A 20-year-old Warmblood broodmare was admitted to evaluate bilateral nasal discharge (primarily left) and difficulty masticating grain, without weight loss. During oral endoscopy, thick purulent discharge (pus) was seen along the palatal gingival attachment of the left maxillary third and fourth premolars (207, 208 Triadan). Nasal endoscopy encountered difficulties owing to an expansile lesion at the level of the left ventral conchal bullae, preventing examination of caudal structures. This enlargement also displaced the nasal septum to the right, obstructing the right common nasal meatus at the level of the right ventral conchal bulla. Radiography localised the anomaly to the left maxillary region, extending over the apices of the left maxillary third and fourth premolars (Triadan 207, 208) and first molar (Triadan 209). The abnormality was large, solitary, round and delineated by a thin bony rim. Further characterisation through computed tomography showed suspected origination from the hard palate, specifically the palatine process of the left maxilla. The abnormality had a mixed attenuation later confirmed to represent gas, pus and feed material. The abnormality communicated with the oral and left nasal cavities and was associated with complete absence of alveolar and compact bone on the medial (palatal) aspect of 207, 208 and 209. Based on the purulent discharge and imaging findings, the abnormality was interpreted as a presumed intraosseous abscess of the hard palate with impacted foreign material and concurrent ipsilateral sinorhinitis and periodontitis. The abscess was debrided, and the horse was treated medically for osteomyelitis, sinorhinitis and periodontitis. All clinical signs resolved within 16 months post-surgery, and the precise source of infection leading to abscess formation remained inconclusive. This case report underscores the role of advanced imaging in diagnosing horses with chronic nasal discharge and explores potential pathogenic mechanisms underlying the development of intraosseous abscesses of the hard palate.