Effect of multi-planar CT image reformatting on surgeon diagnostic performance for localizing thoracolumbar disc extrusions in dogs

Accurate pre-operative localization and removal of disc material are important for minimizing morbidity in dogs with thoracolumbar disc extrusions. Computed tomography (CT) is an established technique for localizing disc extrusions in dogs, however the effect of multi-planar reformatting (MPR) on surgeon diagnostic performance has not been previously described. The purpose of this study was to test the effect of MPR CT on surgeon diagnostic accuracy, certainty and agreement for localizing thoracolumbar disc extrusions in dogs. Two veterinary surgeons and one veterinary neurologist who were unaware of surgical findings independently reviewed randomized sets of two-dimensional (2D) and MPR CT images from 111 dogs with confirmed thoracolumbar disc extrusions. For each set of images, readers recorded their localizations for extruded disc material and their diagnostic certainty. For MPR images, readers also recorded views they considered most helpful. Diagnostic accuracy estimates, mean diagnostic certainty scores and inter-observer agreement were compared using surgery as the gold standard. Frequencies were compared for MPR views rated most helpful. Diagnostic accuracy estimates were significantly greater for MPR vs. 2D CT images in one reader. Mean diagnostic certainty scores were significantly greater for MPR images in two readers. The change in agreement between 2D and MPR images differed from zero for all analyses (site, side, number affected) among all three readers. Multi-planar views rated most helpful with the highest frequency were oblique transverse and curved dorsal planar MPR views. Findings from this study indicate that multi-planar CT can improve surgeon diagnostic performance for localizing canine thoracolumbar disc extrusions.

CT myelography of the thoraco-lumbar spine in 8 dogs with degenerative myelopathy

CT myelography of the T11-L2 region was performed in 8 large-breed dogs with a clinical diagnosis of degenerative myelopathy (DM) and 3 large-breed dogs that were clinically normal. CT myelographic characteristics were recorded for each dog, at each disc level. Area measurements of the spinal cord, dural sac, vertebral canal, and vertebral body were recorded at 4 slice locations for each disc level. Mean area ratios were calculated and graphically compared, by slice location and group. In all dogs, CT myelography identified morphologic abnormalities that were not suspected from conventional myelograms. Characteristics observed with higher frequency in DM versus normal dogs were: spinal stenosis, disc protrusion, focal attenuation of the subarachnoid space, spinal cord deformity, small spinal cord, and paraspinal muscle atrophy. Mean spinal cord: dural sac, spinal cord: vertebral canal, dural sac: vertebral canal, and vertebral canal:vertebral body ratios were smaller in DM versus normal dogs at more than one disc level. Some CT myelographic characteristics in DM dogs were similar to those previously reported in humans, dogs and horses with stenotic myelopathy.