Factors Associated With Intramedullary MRI Abnormalities in Patients With Ossification of the Posterior Longitudinal Ligament

Abstract

A retrospective clinical study of 113 patients with ossification of the posterior longitudinal ligament (OPLL), who underwent either anterior or posterior surgery between 2006 and 2009. To evaluate the risk factors affecting the intramedullary spinal cord changes in signal intensity on magnetic resonance imaging (MRI) for the patients with OPLL. The relationship between the intramedullary spinal cord changes in signal intensity on MRI and neurological deficits, as well as the surgical outcomes, has been described. To obtain better prognosis, early surgery should be conducted in patients with OPLL who have potential abilities to develop intramedullary spinal cord changes in signal intensity on MRI. Various factors may be affecting the development of intramedullary spinal cord changes in signal intensity on MRI. The clinical and radiographic data of 113 patients with OPLL who underwent either anterior or posterior surgery between 2006 and 2009 were reviewed. Age, sex, complication, mean occupying ratio of OPLL (the greatest thickness of OPLL divided by the anteroposterior diameter of the bony spinal canal), duration of symptoms, type of OPLL, preoperative Japanese Orthopedic Association (JOA) score, and range of motion of the cervical spine were collected. Logistic regression analysis was used. Changes in the intramedullary signal intensity on MRI were observed in 33 of the 113 patients. Statistical results show that duration of symptoms, occupying ratio of OPLL, preoperative JOA score, kyphosis, and instability of the cervical spine are the relevant risk factors for intramedullary spinal cord changes in signal intensity on MRI, with regression coefficients of 2.437, 0.953, -1.952, 2.093, and 1.516, respectively. For patients with OPLL, the longer the duration of the symptoms, or the higher occupying ratio of OPLL, or the lower preoperative JOA score, the greater the likelihood of intramedullary spinal cord changes in signal intensity on MRI. As intramedullary spinal cord changes in signal intensity on MRI indicated severe damage to spinal cord and poor prognosis as we described before, early surgery is suggested for patients with OPLL who manifest one of the following factors: prolonged symptoms, high occupying ratio, low preoperative JOA score, kyphosis, or instability of the cervical spine. These factors are closely related to the intramedullary spinal cord changes in signal intensity on MRI.