Unfortunately, the underlying cause of sinus cysts is not known. Whatever the cause, the result is a fluid-filled cyst within the sinuses of a horse that typically occurs unilaterally (on one side of the head only). Because the cyst lining actively secretes fluid into the cyst lumen, it gradually grows and begins to press on the walls of the sinus. Clinical signs include mucoid or blood-tinged nasal discharge, usually from the nostril on the affected side only. The horse may also have swelling or bulging of the facial bones over the sinus cyst due to its expansile nature.
Diagnostics
Radiographs of the skull, Video endoscopy, CT of the horse’s head, Sinoscopy.
Treatment
The only effective treatment for this particular type of cyst is to surgically remove the cyst its lining. This is typically performed either through a large trephination hole or a bone flap, usually under standing sedation with local anesthesia. Once the cyst is removed, recurrence is rare; and the horse’s face typically heals with minimal cosmetic abnormalities. The exception to this is in cases of severe bony deformation, though even these cases can improve to near-normal given enough time.
