Ethmoid hematoma is a progressive and locally destructive disease of horses.
Large hematomas usually start within the ethmoid labyrinth, and smaller ones tend to begin on the sinus floor.
Mild, persistent, spontaneous, intermittent, and unilateral epistaxis is the most common sign clinically.
Diagnosis of the condition is best suited to endoscopy; the lesion can be seen extending into the nasal passages on endoscopic examination and can be demonstrated on radiographs.
Treatment most commonly involves the removal of the complete lesion during a single procedure, via the frontonasal bone flaps; recurrence is likely.