Surgical Removal of a Large Maxillary Sinus Mass Containing Three Dental Structures in a Standing Horse

Dental masses such as odontogenic masses, heterotopic polydontia, or ectopic supernumerary teeth have been documented in the equine head. This is the first case report of a large maxillary sinus mass with 3 ectopic teeth in an adult horse. A 14-year-old warmblood gelding was presented for evaluation of chronic right-sided nasal discharge. After imaging exploration, surgery was performed on the standing horse with a conchofrontal sinus trephination and a large maxillary bone (MB) sinusotomy. The examinations revealed a sinusal mass in the right maxillary sinus covered by sinusal mucosa and surrounding the infraorbital canal. The mass contained 3 ectopic tooth structures. The dental table was complete and normal. Both approaches (right frontal trephination and right maxillary sinusotomy) showed adhesion between the dental structures, the infraorbital canal and the MB. The 2 simultaneous approaches allowed extraction with preservation of all sinus and nerve structures. The loss of integrity of the MB and the attachment of the masses to the infraorbital canal suggests that there could have been damage to the infraorbital canal either prior to or during surgery, with risk of development of neurological symptoms. The complete extraction of these structures in the standing horse has not been previously described, and the use of the 2 approaches allowed good visualization and preservation of the integrity of the sinus structures while allowing complete removal of the mass.