2022 Volume 13 Issue 8 Pages 1024-1029
Introduction: In lumbar isthmic spondylolisthesis, radiculopathy caused by foraminal stenosis are common, but cauda equina symptoms are not a few. In some lumbar isthmic spondylolisthesis patients with cauda equina symptoms, spinal canal stenosis is not serious comparing to degenerative lumbar spinal canal stenosis. In this study, we evaluated the shapes of spinal canal stenosis in lumbar isthmic spondylolisthesis patients by functional imaging of CT myelography.
Methods: In this study, excluding patients who could not be measured because contrast was not depicted due to serious stenosis, 9 patients were included with lumbar isthmic spondylolisthesis who underwent functional imaging of CT myelography at our hospital from July 2017 to May 2021. Anteroposterior diameter, transverse diameter, and cross-sectional area of dural sac were measured in each position with flexion and extension of functional imaging of CT myelography for each case. In addition, the decreasing ratio in the anteroposterior and transverse diameter was calculated. The slices used for the measurements were reconstructed to be parallel to the inferior endplate of slipped vertebra. The height was set at the pars cleft level. For statistical analysis, we conducted a paired t-test. Statistical significance was set at P < 0.05.
Results: The mean anteroposterior diameter was 13.4 mm during flexion and 11.4 mm during extension (P = 0.049). The mean transverse diameter was 14.0 mm during flexion and 11.9 mm during extension (P < 0.001). The mean cross-sectional area was 168.6 mm2 during flexion and 126.7 mm2 during extension (P < 0.01). The decreasing ratio in the transverse diameter was greater than the ratio in the anteroposterior diameter in 5 cases.
Conclusions: All cases showed a decrease in the cross-sectional area of dural sac during extension. In degenerative lumbar spinal canal stenosis, the anteroposterior diameter of dural sac often decreased due to yellow ligament thickening and disc protrusion. On the other hand, in 5 cases of lumber isthmic spondylolisthesis, there was compression from both sides due to the ragged edge, which reduced the transverse diameter more than the anteroposterior diameter. MRI slice was created at only vertebral disc level and not at the pars cleft level. Furthermore, if the anteroposterior diameter does not decrease in the sagittal image, it may not be recognized that the transverse diameter decreases, so the spinal canal stenosis may be underdiagnosed. Therefore, careful attention should be paid to the imaging evaluation of lumbar isthmic spondylolisthesis.
