Translocation of the conus medullaris during dynamic lumbosacral magnetic resonance imaging in dogs

Abstract

OBJECTIVE To investigate the change in the lumbosacral angle (Delta LSA) and conus medullaris (CM) displacement in healthy dogs undergoing dynamic MRI with changes in the posture of their pelvic limbs from neutral posture to flexion or extension posture and to evaluate for potential correlation between Delta LSA and CM displacement. ANIMALS 9 healthy adult Beagles. PROCEDURES Dogs underwent dynamic MRI with their pelvic limbs positioned in neutral, flexion, and extension postures. From T2-weighted sagittal midline plane MRI images, 2 observers measured the lumbosacral angle and CM location in duplicate for each posture for each dog. Intra- and interobserver agreement was assessed, and the Spearman rank correlation coefficient (rho) was used to assess for potential correlation between Delta LSA and CM displacement for changes in pelvic limb posture from neutral to flexion or extension. RESULTS Overall, the mean Delta LSA and CM displacement for changes in posture were 23 degrees and 9.09 mm (caudal displacement) for the change from neutral to flexion posture, 8.4 degrees and -2.5 mm (cranial displacement) for the change from neutral to extension posture, and 32.2 degrees and 11.64 mm (caudal displacement) for the change from extension to flexion posture. The Delta LSA strongly correlated (p = 0.705: 95% CI, 0.434 to 0.859) with displacement of the CM. CONCLUSIONS AND CLINICAL RELEVANCE The use of dynamic MR1, compared with conventional MRI, will better help to characterize clinically normal and abnormal features of the lumbosacral region of the vertebral column and associated spinal cord during postural changes. Further, when limited translocation of the CM is evident on dynamic MRI, veterinarians should suspect underlying lumbosacral pathophysiologic processes or anatomic abnormalities.