Abstract:
Magnetic resonance imaging (MRI) and computed tomography (CT) are commonly used to evaluate dogs with
thoracolumbar myelopathy; however, relative diagnostic sensitivities for these two modalities have not been
previously reported. The purpose of this prospective study was to compare diagnostic sensitivity and observer
agreement for MRI and CT in a group of dogs with thoracolumbar myelopathy due to surgically confirmed
intervertebral disk herniation (IVDH). All included dogs had magnetic resonance (MR) imaging followed by
noncontrast CT using standardized protocols. Three experienced observers interpreted each imaging study
independently without knowledge of clinical or surgical findings. The operating surgeon was aware of MR
findings but not CT findings at the time surgical findings were recorded. Forty-four dogs met the inclusion
criteria. The sensitivity of CT was 88.6% (79.5%–94.2%) and of MR was 98.5% (95% confidence interval,
94.1%–99.7%) for diagnosis of intervertebral disk herniation. Specificity was not calculated, as all dogs
had IVDH at surgery. Magnetic resonance imaging was more accurate than CT for identifying the site
of intervertebral disk herniation-associated spinal cord compression and differentiating disk extrusion vs.
protrusion. Computed tomography was less accurate for lesion localization in per acute cases, as well as
for chondrodystrophic, female, older and smaller (<7 kg) dogs. Inter-rater agreement was good for lesion
lateralization for bothMR and CT (κ = 0.687, 95% CI = 0.552, 0.822, P = 0.002, and κ = 0.692, 95% CI =
0.542, 0.842, P = 0.003). Findings from the current study indicated that MR imaging was more sensitive and
accurate than noncontrast CT for diagnosis and characterization of thoracolumbar myelopathy due to IVDH
in dogs. C
