腰椎椎間板ヘルニアの自然経過 ＭＲＩからの検討

Abstract

MR images provide valuable information on herniated lumbar intervertebral disc. In this report, we discuss the natural history of intervertebral discs based on signal intensity data for herniated discs obtained from T2-weighted MR images. Forty-seven patients with lumbar disc herniation were examined by MRI. On the T2-weighted sagittal MRI image, we measured the signal intensity of herniated material and the orignating nucleus pulposus. The ratio of signal intensity in the herniated material to that in the nucleus was determined and designated as the signal intensity ratio (SIR). We divided patients into three groups according to SIR data, high SIR with a ratio of 1.2 or more, iso SIR with a ratio of 0.8 to 1.2, and low SIR 0.8 or less. The relationship between SIR and duration of illness was evaluated. In seven patients, who were re-examined by MIR at six months, changes in the herniated material size were valuated. The duration of illness was 22.2±16.0, 44.4±53.3 and 123.9±54.5, in the high, iso and low SIR groups, respectively. The value in the low SIR group was significantly longer than the value in the other two groups. A significant relationship was observed between SIR and duration of illness on the negative exponential curve. These results suggested that SIR would become high immediately following herniation and thereafter decrease with increasing duration of illness. In the patientes who were re-examined by MRI, two were in the high SIR group and four in the low SIR group. Although herniated material in all two patients in the high SIR group was noted to be smaller at the time of follow-up, no such change was noted in the other patients. This result suggested that high SIR may indicate that the reaction of water imbibition and inflammation in the herniated material would occur, and in low SIR, the reaction would be finished.