Diagnostic Imaging of the Equine Head: Which Modality for Which Disease?

The complex anatomy and resulting superimposition of bony and soft tissue structures makes the interpreting of skull radiographs difficult. However, radiography is widely available and provides a good survey in standing horses; however, an accurate technique is mandatory. Standard views include a straight latero-lateral view; 30-45° oblique views are essential for the separation of the left and right side. The ventrodorsal view is more difficult to obtain in standing horses, but might be very helpful to differentiate between unilateral and bilateral disease and to evaluate the lateral compartment of the maxillary sinus, given and adequate technique. Diseases of the nasal passages and paranasal sinuses do almost always result in a decreased content of air which causes a decrease of contrast between the bony structures and the air filled passages. If there is fluid within the sinuses, horizontal fluid lines can be identified. If fluid is entrapped within cysts or abscesses, there is radiographically no difference to other soft tissue lesions, such as granuloma, hematoma or neoplastic lesions. Additional parameters such as location, extent, destruction of bone, mass effect on surrounding structures or concurrent tooth root alterations may lead in these cases to a radiographic differentiation. Radiography has been reported to be 81% sensitive in sinonasal diseases, but was diagnostically useful in only 36 %. […]