[Updates on ossification of posterior longitudinal ligament. Image diagnosis of ossification of posterior longitudinal ligament and associated diseases].

Ossification of posterior longitudinal ligament (OPLL) is often diagnosed on lateral plain radiograph, but sometimes overlooked on plain films. Computed tomography (CT) is more sensitive to visualize the ossified mass. Cervical OPLL is often accompanied by other spinal ossification including thoracic ossification of the ligamentum flavum. High intensity area within the spinal cord on T2-weighted MR images is strongly correlated with the responsible level of myelopathy, which is useful to differentiate other spinal cord lesions including Parkinsonism, multiple sclerosis, motor neuron diseases. Neurologic level diagnosis combined with image diagnosis is very important to identify responsible level.