Equine Sinusitis Study Guide

Overview and Clinical Importance

Equine sinusitis is the most common disease affecting the paranasal sinuses in horses. It represents an inflammatory condition of the sinus mucosa that can be either primary (resulting from upper respiratory tract infection) or secondary (caused by an underlying condition such as dental disease). Understanding the complex anatomy of the equine paranasal sinuses, recognizing clinical presentations, and selecting appropriate diagnostic and treatment modalities are essential skills for the NAVLE examination.

The equine paranasal sinus system consists of seven paired compartments: frontal, dorsal conchal, ventral conchal, rostral maxillary, caudal maxillary, sphenopalatine, and middle conchal (ethmoidal) sinuses. The prevalence of sinusitis is approximately 0.4% based on large population studies, but it remains a clinically significant condition due to its chronic nature and potential treatment challenges.

Anatomy of the Paranasal Sinuses

The equine paranasal sinuses are air-filled cavities within the skull that develop by evagination into the spongy bone between the external and internal plates of cranial and facial bones. Each sinus is lined by respiratory epithelium (pseudostratified ciliated columnar epithelium with goblet cells) and has direct or indirect communication to the nasal cavity.