Cone beam computed tomographic myelography in horses with cervical vertebral compressive myelography

<p><strong>Background</strong>: While computed tomographic (CT) myelography is increasingly available and has been evaluated in alive horses, objective criteria for diagnosing cervical vertebral compressive myelopathy (CVCM) are lacking.</p> <p><strong>Objectives</strong>: Establish morphometric dimensions of cervical vertebral canal and spinal cords from horses with CVCM and compare those to unaffected horses with the use of cone beam CT (CBCT).</p> <p><strong>Study design</strong>: Prospective observational study.</p> <p><strong>Methods</strong>: Four control horses and ten horses with CVCM underwent diagnostic imaging and histopathology. Morphometric measurements were obtained from cervical radiographs and radiographic and CBCT myelography. Receiver operating characteristic curves were generated to establish thresholds of measurements.</p> <p><strong>Results</strong>: Intravertebral sagittal ratios were significantly different between CVCM and control horses. Dorsal myelographic column reduction was significantly different between compressed site and non-compressed sites. Full myelographic area (FMA), dural area (DA), and spinal cord area (SCA) were significantly smaller in the CVCM horses, and were significantly smaller at compressed sites when compared to non-compressed sites. Reductions of FMA and DA and ratios of spinal cord area to full myelographic and dural area were significantly larger at compressed sites when compared to non-compressed sites. Diagnostic thresholds to consider for CVCM are FMA<294mm², DA<188mm², and SCA <104mm². Compressed sites were associated with thresholds of FMA<274mm², DA<188mm², or reduction of FMA>9%, reduction of DA>14%, SCA:FMA>36.7%, and SCA:DA>57.9%.</p> <p><strong>Main limitations</strong>: Small number of horses. CVCM horses were younger than control horses.</p> <p><strong>Conclusions</strong>: CBCT myelography provides quantitative parameters that can support a diagnosis of CVCM and should be used alongside radiographic myelography.</p>