Determinants of spontaneous resorption of intervertebral disc herniations

Study Design. A follow-up of disc herniation ( herniated nucleus pulposus [HNP]) resorption on magnetic resonance imaging (MRI). Objective. To assess the determinants of resorption of HNP. Summary of Background Data. Neovascularization in the outermost areas of HNP, presenting as an enhancing rim in gadolinium diethylenetriamine pentaacetic acid MR images, is thought to be a major determinant of spontaneous resorption of HNP. Methods. Patients with HNP-induced sciatica at baseline were rescanned at 2 months (N = 74) and after 12 months (N = 53). The volume of HNP (mm(3)), thickness (mm) and extent (%) of enhancement, and the degree of HNP migration (Komori classification) were analyzed. Repeated measures analysis of covariance was used in statistical analysis. Results. Significant resorption of HNP occurred from baseline to 2 months, although the resorption rate was more pronounced over the whole 1-year follow-up. Higher baseline scores of rim enhancement thickness, higher degree of HNP displacement in the Komori classification, and age category 41-50 years were associated with a higher resorption rate. Thickness of rim enhancement was a stronger determinant of spontaneous resorption than extent of rim enhancement. Clinical symptom alleviation occurs concordantly with a faster resorption rate. Conclusions. MRI is a useful prognostic tool for identifying patients with HNP-induced sciatica with a benign natural course.