In recent years, many authors have reported that an extruded lumbar intervertebral disc was absorbed through phagocytosis and dehydration. However, absorption of an extruded cervical intervertebral disc has rarely been repoted. We have investigated the follow-up MRI of all 24 patients with cervical disc herniation seen between 1991 and 1995. Of these, 8 patients with radiculopathy and 7 with myelopathy had been treated nonoperatively, and a further 9 patients with severe myelopathy had undergone expansive laminoplasty. In follow-up MRI, a reduction in the size of the extruded disc was seen in 5 of the 15 nonoperative patients and in 8 of the 9 operative patients. The 9 operative patients showed a mean recovery rate of 68.4±15.2% (range from 44 to 90%) according to their JOA score. In the nonoperative group, recovery of symptoms was seen in all 5 patients with reduction, and in only 4 of 10 patients with nonreduction. The initial MRI of the 5 patients with reduction was taken between 2 and 7 weeks (mean 4 weeks) after onset, and between 1 month and 14 years (mean 13 months, not including the one at 14 years) after onset in the 10 patients with nonreduction. The initial MRI of the 9 operative patients was taken between 1 month and 6 years (mean 14 months after onset). The pathomechanism for disc reduction was concluded to have been the same as for lumbar disc herniation in the nonoperative patients. However, the pathomechnism in the operative patients was inconclusive and was likely to be different from that in the nonoperative patients.
