Accuracy, intermethod agreement, and inter-reviewer agreement for use of magnetic resonance imaging and myelography in small-breed dogs with naturally occurring first-time intervertebral disk extrusion

Bos AS, Brisson BA, Nykamp SG, et al. 

Journal of the American Veterinary Medical Association 2012;240:969-977.

OBJECTIVE: To determine accuracy, intermethod agreement, and inter-reviewer agreement for multisequence magnetic resonance imaging (MRI) and 2-view orthogonal myelography in small-breed dogs with first-time intervertebral disk (IVD) extrusion. DESIGN: Prospective evaluation study. ANIMALS: 24 dogs with thoracolumbar IVD extrusion. PROCEDURES: Each dog underwent MRI and myelography. Images obtained with each modality were independently evaluated and assigned standardized scores in a blinded manner by 3 reviewers. Results were compared with surgical findings. Inter-reviewer and intermethod agreements were assessed via kappa statistics. Accuracy was assessed as the percentage of dogs for which >/= 2 of 3 reviewers recorded findings identical to those determined surgically. RESULTS: Inter-reviewer agreement was substantial for site (kappa = 0.70) and side of IVD extrusion (kappa = 0.62) in T2-weighted magnetic resonance images and was substantial for site (kappa = 0.72) and fair for side of extrusion (kappa = 0.37) in myelographic images. Agreement for site between each modality and surgical findings was near perfect (kappa = 0.94 and 0.88 for MRI and myelography, respectively). Intermethod agreement was substantial for site (kappa = 0.71) and moderate for side of extrusion (kappa = 0.40). Accuracy of MRI for site and side was 100% when results for T1-weighted, T2-weighted, and contrast-enhanced T1-weighted sequences were combined. Accuracy of myelography was 90.9% and 54.5% for site and side, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Agreement between imaging results and surgical findings for identification of IVD extrusion sites in small-breed dogs was similar for MRI and myelography. However, MRI appeared to be more accurate than myelography and allowed evaluation of extradural compressive mass composition.