<jats:title>Abstract</jats:title> <jats:sec id="s001"> <jats:title>OBJECTIVE</jats:title> <jats:p>To quantify the degree of dural compression and assess the association between site and direction of compression and articular process (AP) size and degree of dural compression with CT myelography.</jats:p> </jats:sec> <jats:sec id="s002"> <jats:title>ANIMALS</jats:title> <jats:p>26 client-oriented horses with ataxia.</jats:p> </jats:sec> <jats:sec id="s003"> <jats:title>PROCEDURES</jats:title> <jats:p>Spinal cord-to-dura and AP-to-cross-sectional area of the C6 body ratios (APBRs) were calculated for each noncompressive site and site that had > 50% compression of the subarachnoid space. Site of maximum compression had the largest spinal cord-to-dura ratio. Fisher exact test and linear regression analyses were used to assess the association between site and direction of compression and mean or maximum APBR and spinal cord-todura ratio, respectively.</jats:p> </jats:sec> <jats:sec id="s004"> <jats:title>RESULTS</jats:title> <jats:p>Mean ± SD spinal cord-to-dura ratio was 0.31 ± 0.044 (range, 0.20 to 0.41) for noncompressive sites and 0.44 ± 0.078 (0.29 to 0.60) for sites of maximum compression. Sites of maximum compression were intervertebral and extra-dural, most frequently at C6 through 7 (n = 10), followed by C3 through 4 (6). Thirteen horses had dorsolateral and lateral compression at the AP joints, secondary to AP (n = 7) or soft tissue proliferation (6). Site significantly affected direction of compression, and directions of compression from occiput through C4 were primarily ventral and lateral, whereas from C6 through T1 were primarily dorsal and dorsolateral. No linear relationship was identified between mean or maximum APBR and spinal cord-to-dura ratio.</jats:p> </jats:sec> <jats:sec id="s005"> <jats:title>CONCLUSIONS AND CLINICAL RELEVANCE</jats:title> <jats:p>CT myelography may be useful for examination of horses with suspected cervical compressive myelopathy. Degree of compression can be assessed quantitatively, and site of compression significantly affected direction of compression.</jats:p> </jats:sec>