We do not know what the causes sinus cyst. A cyst with a lining that secretes fluid will develop in a horse’s sinus. Clinical signs include mucoid or blood tinged nasal discharge from one or both nostrils. The horse may also have swelling or bulging of the facial bones over the sinus cyst.
Radiographs of the skull, video endoscopy, CT of the horse’s head
The only treatment is to remove the cyst and lining for the cyst. This is done through a sinus flap. A sinus flap involves opening a flap of bone into the sinus. The horse’s face will heal with minimal cosmetic defects following surgery.