Identification of Normal Horse Head Structures, with Special Reference to Paranasal Sinuses, by Anatomical Cross-section and Magnetic Resonance Imaging (MRI)

The purpose of this report was to describe the axial appearance of the normal horse head with special reference to the paranasal sinuses using magnetic resonance imaging (MRI) technique and anatomical cross sections. In order to do this, T1 (longitudinal relaxation time)-weighted, 1cm –thick images of horse cadaver heads (n=5) were captured using closed magnet of a 1-Tesla (field strength). Afterwards, the frozen heads were cross-sectionally sliced at seven planes (from the level of upper and lower incisors to the level of perpendicular plate of ethmoidal bone) according to MRI slices thickness, and then correspondingly compared with the MRI images. The obtained data (per each plane) properly defined the normal anatomical features of the normal horse head by both anatomical cross-sections and MR images. The MR images from this investigation provided a clear definition of normal horse head structures and were consistent with that of gross anatomical sections. The T1-weighted images showed that the mineral-rich tissues (bones and teeth) appeared dark (no signal), cartilages and muscles appeared grey (low signal intensity, hypointense), and fat (subcutaneous and within bone marrow) appeared bright (high signal, hyperintense). The air-containing sinuses and conchae appeared dark without signals. As this study demonstrates normal horse head structures with a particular attention to nasal cavity structures and its relation to five types of paranasal sinuses, it could be used as a landmark and reference to properly diagnose various surgical disorders of head region particularly paranasal sinuses that are the most common in horses.