Effect of Ventral Slot Procedure on Spinal Cord Compression in Dogs with Single Static Intervertebral Disc Disease: Preliminary Findings while Evaluating a Semiquantitative Computed Tomographic Myelographic Score of Spinal Cord Compression

Abstract

To (1) evaluate pre- and postoperative cervical spinal cord compression (SCC) in the context of uncomplicated ventral slot (VS) decompression using computed tomographic (CT) myelography and (2) report reliability of a semiquantitative SCC score using CT myelography. Prospective and retrospective, clinical pilot study. Dogs (n = 17) with single static intervertebral disc disease. On matched pre- and postoperative transverse CT myelographic images, degree and lateralization of extradural SCC were scored by 4 blinded independent observers, followed by consensus finding. Inter- and intraobserver variability was quantified using intraclass correlation (ICC). Nonparametric tests were performed comparing pre- and postoperative SCC, correlation with neurologic status and significance of lateralization. Because of invisible contrast agent, only 13 dogs could be fully evaluated. After VS, SCC was significantly reduced whereas neurologic function significantly improved. Ten dogs had residual compression, not affecting neurologic long-term outcome. Only preoperative compression score and neurologic status 3-7 weeks postoperatively were inversely correlated. Lateralization of SCC preoperatively did not affect postsurgical compression scores. Interobserver ICC was 0.848 and intraobserver ICC was 0.984. VS improves neurologic function but often fails at completely resolving extradural SCC. The proposed CT myelographic score is highly reliable, assuring consistency among and within observers.