The radiological characteristics associated with the development of myelopathy due to ossification of the posterior longitudinal ligaments at each responsible level based on spinal cord evoked potentials.

STUDY DESIGN: This was a retrospective study of prospectively collected data.

OBJECTIVE: This study aimed to characterize the factors associated with the development of myelopathy at each cervical level based on spinal cord evoked potentials (SCEPs) and radiological parameters in patients with cervical ossification of the posterior longitudinal ligament (OPLL).

SUMMARY OF BACKGROUND DATA: Static factors, dynamic factors, and combinations of these factors are associated with the development of OPLL-related myelopathy.

PATIENTS AND METHODS: Fifty patients with OPLL were enrolled in this study. They underwent kinematic computed tomography myelography (CTM), MRI, and X-ray examinations, and the levels responsible for their myelopathy were determined by intraoperatively assessing SCEPs. C2-7 lordosis, C2-7 range of motion (ROM), and segmental ROM were assessed on the midsagittal view during flexion and extension and in the neutral position using the Cobb method, and the cross-sectional area of the spinal cord (CSA) was measured on the axial view in each neck position using kinematic CTM. The cervical levels were classified into responsible (Group R) and non-responsible (Group N) levels.

RESULTS: The responsible level was C3-4, C4-5, C5-6, and C6-7 in 18, 23, 18, and 4 patients, respectively. In the multivariate analysis, the CSA was significantly smaller in Group R than in Group N at all responsible levels, but the dynamic change in the CSA was only associated with myelopathy at the C3-4 and C4-5 levels.

CONCLUSION: Myelopathy at the C3-4 level was more strongly associated with dynamic factors and a shorter disease duration, than myelopathy at the C5-6 level. This study provides useful information for assessing the pathophysiology of OPLL-related cervical myelopathy and managing the condition.