THE NATURAL COURSE OF MYELOPATHY CAUSED BY OSSIFICATION OF THE POSTERIOR LONGITUDINAL LIGAMENT IN THE CERVICAL-SPINE

The natural course of ossification of the posterior longitudinal ligam ent, particularly the relationship between the onset of myelopathy and factors associated with its aggravation, was studied in 207 patients during an average period of 10 years 3 months. Myelopathic signs were already present in 37 (18%) patients at the time of the initial examin ation. Fourteen of these 37 patients showed aggravation of symptoms du ring the observation period. Myelopathy appeared during the observatio n period in 33 (16%) of the 207 patients. One hundred thirty-seven (66 %) patients were free of myelopathy. Some patients had no myelopathic signs, despite severe spinal stenosis, because of the ossification. In these patients, the range of motion of the cervical spine was severel y limited, indicating that dynamic factors are important in the develo pment of myelopathy. In treating this disease, it is necessary to take into consideration the natural course of the disease and to identify the involvement not only of static factors, such as compression caused by ossification, but also of dynamic factors.