1:48 Utility of magnetic resonance imaging parameters in predicting highly sensitive discs on discography

Abstract

Purpose of study: The pain threshold of a disc, defined as the stimulus intensity at which pain occurs, can be measured by monitoring intradiscal pressure during discography procedure, a technique known as pressure-controlled discography. This allows quantification of the sensitivity of the disc. Previous research has demonstrated that the sensitivity of discs varies greatly and that subgroups of discs, defined by their pain thresholds, can be identified. A number of lines of evidence suggest that the most sensitive discs on discography, the highly sensitive (HS) subgroup, constitute “true positive” discs and that other factors, such as nervous system sensitization, may be responsible for the decreased pain thresholds in other groups. A number of studies have examined the ability of magnetic resonance imaging (MRI) parameters to predict positive discs on discography. None, however, have examined the ability of MRI parameters to predict highly sensitive discs on discography. The objective of this study was to define the ability of MRI to predict HS discs.Methods used: In 208 patients (634 discs) both MRI and pressure-controlled discography were obtained. Six MRI variables were defined: high intensity zone, annular tear, nuclear signal on T2-weighted image, disc narrowing, disc contour and bone marrow intensity change. Discs were classified as HS on discography if there was concordant pain provocation greater than or equal to 6/10 with abnormal morphology at a distending pressure less than 27 psi.of findings: Cross-tabulations showed that MRI parameters and classification of the disc as positive high sensitive were significantly interdependent (chi squared ≥27, p<.0005, for all MRI parameters). The most reliable predictors of HS discs were HIZ grade III, BMIC, extrusion, radial and concentric tear, each of which had a specificity of greater than 95%. Sensitivity was 89% for moderate nuclear signal loss and was low for all other MRI parameters.Relationship between findings and existing knowledge: Previous studies have not consistently shown MRI parameters and HIZ in particular to be predictors of positive discography. Present results show that higher grades of HIZ do predict the HS subgroup of positive discs. Side by side with HIZ BMIC, extrusion, radial and concentric tear can be predictors of positive disc with low pain threshold. At the same time absence or low grades of HIZ cannot provide any confident information on disc condition.Overall significance of findings: For the first time, the MRI parameters that identify an HS disc on discography have been identified. Identification of the HS subgroup is of particular importance in presurgical planning, because HS discs on discography appear to respond well to interbody fusion. Because of low sensitivity, however, MRI cannot replace discography in identifying HS discs.Disclosures: No disclosures.Conflict of interest: No conflicts.