Schmorl's nodes on magnetic resonance imaging. Their incidence and clinical relevance.

Schmorl's nodes were observed in 76 (19%) of 400 patients with lumbar symptoms, and in 10 (9.4%) of 106 control patients. In the lumbar group, the highest incidence was 57%, in the second decade of life, and the lowest was 5%, in the sixth decade of life. Using MRI, among both groups, a total number of 218 Schmorl's nodes were observed at 170 disc levels; however, plain x-ray revealed only 73 (33%) of them. There were associated posterior disc herniations at 39 disc levels in 30 cases (39%), most of which were at the L4/5 level. The ratio of the cases showing only Schmorl's nodes to those with associated disc herniations at the same level increased markedly with age. Three of the four teenaged patients with multiple Schmorl's nodes at four or more disc levels had a history of hard sports. Schmorl's nodes, therefore, appear to be a type of vertical disc herniation, and to be an important pathognomonic condition, especially for young people.