Computed Tomographic Assessment of Individual Paranasal Sinus Compartment and Nasal Conchal Bulla Involvement in 300 Cases of Equine Sinonasal Disease

Abstract

Background: Computed tomographic (CT) imaging has allowed new anatomical studies and detailed clinical imaging of the complex, overlapping equine sinonasal structures. Despite the widespread use of CT, no study has specifically identified which compartments are most commonly affected with sinus disorders. CT has also shown the presence of intercurrent, ipsilateral nasal disorders, especially infection of the nasal conchal bullae (NCB) in many cases of sinus disease, but the frequency of intercurrent NCB infections has not been reported. Objectives: To identify which sinus compartments are most commonly affected in horses with clinical sinus disorders and to record the prevalence of NCB involvement in such cases. Study Design: Retrospective examination of CT images of horses with confirmed unilateral sinus disease. Methods: The CT images of 300 horses, from three different equine hospitals with clinically confirmed sinus disease [mainly dental (53%) and primary sinusitis (25.7%)] were retrospectively examined to determine which sinus compartments and NCBs were affected. Results: The rostral, more dependent sinus compartments were most commonly involved, i.e., the rostral maxillary sinus in 284/300 (94.7% affected) and the ventral conchal sinus (87% affected). The caudal maxillary sinus (65.3%), dorsal conchal sinus (52.7%), frontal sinus (26%), ethmoidal sinus (32%) and sphenopalatine sinus (28.7%) were less commonly affected. There was infection or destruction of the ipsilateral NCBs in 56% of horses with sinus disorders, including the ventral NCBs in 42.3%, dorsal NCBs in 29% and both NCBs in 18% of cases. Main Limitations: The horses with sinonasal disease that underwent head CT imaging include more problematic cases and horses of high value, rather than the general horse population. Dixon et al. Equine Sinonasal Disease Conclusions: The more dependant (i.e., the RMS and VCS) sinus compartments are most commonly involved in sinus disorders, with the RMS involved in nearly every case. The more dorsally located sinuses (i.e., caudal group) are less commonly involved. Many horses with sinus disease also have disorders of their nasal conchal bullae and so the term sinonasal disease seems appropriate for these disorders.

A long‐term study of sinoscopic treatment of equine paranasal sinus disease: 155 cases (2012–2019)

“…This is likely due to increasing awareness of these middle meatus lesions, the use of CT 13 and more careful endoscopic examination of this area. A recent multicentre CT study of 300 horses found an overall prevalence of NCB lesions (infection or loss) in 56% of horses with sinus disease 5 …”

“…However, those treatments usually involved sinusotomy and nasal fistulation, that along with prolonged sinus lavage, likely dislodged inspissated exudate and sequestrae from the middle meatus or NCB, as well as from the sinuses, thus resolving any concurrent nasal problem. The presence of complete loss of NCB with distortion and adjacent nasal conchal changes in some horses with sinusitis 5 indicates that some infected NCBs are fully lost, thus allowing resolution of the nasal middle meatus inflammation.…”

“…Equine paranasal sinus disorders (“sinusitis”) are usually chronic diseases where it can be difficult to establish the precise cause 1‐5 and sometimes to effectively treat 6,7 . Sinusitis can be termed “primary” when no underlying cause is identified for the sinus inflammation.…”

“…Sinusitis can be termed “primary” when no underlying cause is identified for the sinus inflammation. Sinusitis is termed “secondary” when underlying causes including cheek teeth apical infections, oro‐maxillary fistula (OMF), sinus cysts, intra‐sinus progressive ethmoid haematoma (PEH) and tumours, or sinus trauma are identified 1‐5 . Recent studies have highlighted the occurrence of concurrent ipsilateral nasal disease with sinusitis, including the presence of sino‐nasal fistulae, inspissated exudate or bone sequestrae 2,3,4,8,9 and infected nasal conchal bullae (NCB) 5,8,10 …”

Multidetector CT and cone‐beam CT have substantial agreement in detecting dental and sinus abnormalities in equine cadaver heads

“…Imaging of the equine head with MDCT has been well described 7,16–25 and comparisons between MDCT and CBCT have been reported in the human literature 11,14,15,26 . Sparse information is available on their comparison in small animal imaging 12,27,28 and no studies have compared CBCT and MDCT for equine head imaging.…”