Progressive Ethmoid Hematoma in Horses

Progressive ethmoid hematoma is a widely recognized disease process in horses but has an incompletely understood etiopathogenesis. The mass lesion of progressive ethmoid hematoma expands by repeated hemorrhage and is usually extensive when a diagnosis is made. Diagnostic techniques (e.g., upper airway endoscopy, radiography, computed tomography) aid in determining the extent of a progressive ethmoid hematoma. Definitive diagnosis is determined by histopathologic examination. Treatment is based on location, size, and extent of the lesion, along with consideration of economics and equipment availability. Multiple treatment options are available, including surgical resection, surgical reduction with application of cryogens or laser therapy, and intralesional formalin injection. Despite treatment, prognosis for long-term resolution remains guarded to poor due to high rates of recurrence. Progressive ethmoid hematoma is an uncommon, nonneoplastic condition of the nasal passages and paranasal sinuses of horses. Although progressive ethmoid hematoma is a well-known clinical entity, its etiopathogenesis is incompletely understood. Modern diagnostic equipment is helpful in determining the extent of the lesions. This article provides an overview of the disease, diagnosis, and available treatments for progressive ethmoid hematoma in horses. BACKGROUND/SIGNALMENT The clinical and pathologic signs associated with progressive ethmoid hematoma have been available for some time as retrospective case reviews date to the 1930s. However, the etiopathogenesis is incompletely understood. Prevalence of progressive ethmoid hematomas in hospital populations is reported at 0.03% to 0.04% (1 in 2500 horses). Horses with progressive ethmoid hematomas have been reported to represent 4% of horses with disease of the nasal cavity and paranasal sinuses and 10% of horses undergoing nasal or sinus surgery. Progressive ethmoid hematomas have been reported in horses from 4 weeks to 20 years of age, with a mean of 9.9 years reported in one review. There appears to be an increased likelihood of a progressive ethmoid hematoma forming as age increases. The prevalence among males and females is statisCE 1094 Vol. 23, No. 12 December 2001 n The etiology of progressive ethmoid hematoma remains unknown; however, progression of the hematoma occurs by repeated subcapsular