Transverse CT image through the rostral sinus compartments at the level of Triadan 10 of a horse with dental sinusitis caused by a Triadan 210 apical infection. The 210 has changes in its buccal root, widened periodontal space, and alveolar bone remodeling. There is resultant empyema of the VCS, DCS, and RMS (with gas bubbles in the latter). There is also thickening of the maxillary septal bulla bone and swollen mucosa on both sides (white arrow), some expansion and wall thickening of the infraorbital canal (yellow arrow) and grossly thickened maxillary bone (red arrow). L, left; R, right.