• navicular syndrome;
  • magnetic resonance imaging;
  • computed tomography;
  • radiography;
  • histopathology;
  • horse

Radiographic evaluation of navicular syndrome is problematic because of its inconsistent correlationwith clinical signs. Scintigraphy often yields false positive and false negative results and diagnosticultrasound is of limited value. Therefore, we assessed the use of computed tomography and magneticresonance imaging in a horse with clinical and radiographic signs of navicular syndrome. Cadaverspecimens were examined with spiral computed tomographic and high-field magnetic resonance scanners and images were correlated with pathologic findings. Radiographic changes consisted of bonyremodeling, which included altered synovia! fossae, increased medullary opacity, cyst formation andshape change. These osseous changes were more striking and more numerous on computed tomographic and magnetic resonance images. They were most clearly defined with computed tomography. Many osseous changes seen with computed tomography and magnetic resonance imaging were notradiographically evident. Histologically confirmed soft tissue alterations of the deep digital flexortendon, impar ligament and marrow were identified with magnetic resonance imaging, but not withconventional radiography. Because of their multiplanar capability and tomographic nature, computedtomography and magnetic resonance imaging surpass conventional radiography for navicular imaging, facilitating earlier, more accurate diagnosis. Current advances in imaging technology should makethese imaging modalities available to equine practitioners in the future.