Correlative imaging findings in seven dogs and one cat with spinal arachnoid cysts

Information regarding 7 dogs and 1 cat with a spinal arachnoid cyst is pres ented. All patients were evaluated with survey radiographs and myelography. Computed tomography (CT) following myelography, magnetic resonance (MR) im aging, and sonography, were used in some of the patients. These imaging tec hniques were evaluated to determine their efficacy in diagnosing arachnoid cysts, ascertaining the extent and internal cyst architecture and detecting associated spinal cord abnormalities. Survey radiographs were nondiagnosti c in all patients. Myelographically, the arachnoid cyst was visible in all patients, with partial blockage to flow of contrast medium. CT provided add itional information on localization and lateralization of the cyst, and all owed measurement of the degree of spinal cord compression. MR imaging enabl ed identification of an associated syringomyelia. Sonography was useful for defining the cyst wall and characterizing the internal architecture of the cyst cavity and adjacent spinal cord. Measurements of the degree of spinal cord compression could be made and were similar to measurements made from CT. Additionally, sonography was considered a useful technique for orientat ing the surgeon to the location and extent of the cyst. In the absence of t he availability of CT or MR imaging for evaluating patients with an arachno id cyst, sonography is considered a valuable technique for directly assessi ng the spinal cord for associated disease. Decompressive surgery was perfor med on 4 dogs and 1 cat, all with successful outcomes.