Serial changes on MRI in lumbar disc herniations treated conservatively.

Using serial MRI, we studied 32 patients with herniated lumbar discs, treated conservatively, to clarify the natural history of this condition. MRI was performed in the acute stage, then 6 months and 1 year later. On axial images, the proportion of the cross-sectional area of the spinal canal occupied by the herniated disc was 31.9% on the average on the initial scan, 28.7% 6 months and 25.3% 1 year later. The size of the herniation decreased by more than 20% in 11 patients (34%), by 10-20% in 8 (28%) and was unchanged in 12 (38%). The height of the disc slightly decreased with time, but there was no significant change in the angle of lordosis in the affected segment. The initial MRI revealed degeneration of all affected discs, and progressive degeneration was observed in 9 patients. The more degenerate the disc and the larger the initial herniation the more the size of the herniated fragment decreased.