Spontaneous resolution of lumbar disk herniation: predictive signs for prognostic evaluation

Spontaneous regression of lumbar disk herniation in patients who did not undergo surgery nor interventional therapy is reported in up to 70% of cases; however, no perspective study has clarified the possible predictive signs of a positive evolution. Aim of our study was to search for plan and contrast enhancement MRI signs able to define disk-herniation resolution. We enrolled 64 patients, affected by 72 lumbar disk herniations as per the classification proposed by the American Society of Neuroradiology (Nomenclature and Classification of Lumbar Disk Pathology 2001). MRI examinations were performed by 1.5-T magnet, using T1w SE sequences on sagittal and axial planes, before and after contrast, and T2w FSE ones on the same planes. The following parameters were considered: age, sex, level and size of disk herniation, its relationship to the spinal canal, clinical onset interval, type of disk herniation, herniated-material signal intensity on T2w sequences and its pattern of contrast enhancement. All the patients, conservatively treated, underwent clinical and MRI follow-up examination after 6 months. At MRI follow-up exams spontaneous regression of disk herniation was observed in 34.72% of cases. Among these, free fragments regressed in 100% of cases, herniations with high signal intensity on T2w sequences in 85.18%, herniations with peripheral contrast-enhancement in 83% of cases. Disk-herniation evolution did not show any relationship with location, size and level. Our study demonstrates that MRI, in addition to its high diagnostic value, offers predictive information about disk-herniation evolution.