Preoperative and postoperative magnetic resonance image evaluations of the spinal cord in cervical myelopathy.

To evaluate the morphologic changes of the spinal cord in patients with cervical myelopathy due to cervical spondylosis and ossification of the posterior longitudinal ligament, the authors measured the thickness and signal intensity of the cervical cord with magnetic resonance imaging in healthy adults and patients with cervical myelopathy, and compared these findings. In patients with cervical myelopathy, the preoperative and postoperative magnetic resonance imaging findings were compared with the severity of myelopathy and postoperative results. In healthy adults, the anteroposterior diameter of the cervical cord was 7.8 mm at the C3 level and decreased at lower levels. In the patients with cervical myelopathy, the preoperative spinal anteroposterior diameter was significantly reduced at various levels corresponding to the stenosis site within the vertebral canal. In the group with ossification of the posterior longitudinal ligament, the minimal anteroposterior diameter of the cervical cord tended to decrease with increasing severity of myelopathy. However no relationship was observed between the two parameters in the cervical spondylotic myelopathy group. In the group with ossification of the posterior longitudinal ligament, surgical results were good when the postoperative anteroposterior diameter was increased, whereas in the cervical spondylotic myelopathy group there was no relationship between the two parameters. In the patients with myelopathy, a high intensity area was observed in about 40% of all patients before operation and about 30% after operation. However, the presence or absence of a high intensity area did not correlate with the severity of myelopathy or with surgical results in the group with ossification of the posterior longitudinal ligament and the cervical spondylotic myelopathy groups.