Courses of cervical disc herniation causing myelopathy or radiculopathy

Study Design. The courses of protruded masses in cervical disc herniations were traced on preoperative computed tomography discograms of patients with myelopathy or radiculopathy. Objective. To characterize the courses of protruded masses in cervical disc herniation. Summary of Background Data. No studies have been reported on the varied courses of protruded masses in cervical disc herniation. Methods. This study investigated the preoperative CT discograms of 150 patients with myelopathy and 50 patients with radiculopathy who had undergone anterior cervical discectomy and fusion for disc herniation. The courses of herniations were traced from the penetration sites on the deep layer of the posterior longitudinal ligament through their locations in the spinal canal, and were divided into one median, two paramedian, and two lateral sections. Results. Of the 150 discs in the patients with myelopathy, 87% had a median penetration and 13% had a paramedian one. No discs had a lateral penetration. It was found that 45% of the median penetrations led to median herniation through a straight course and 55% to paramedian herniation through an oblique course, and that 95% of the paramedian penetrations led to paramedian herniation through a straight course. Of the 50 discs in the patients with radiculopathy, 70% had a median penetration, 26% a paramedian penetration, and 4% a lateral penetration. Lateral penetration was observed only at C7-T1. All of the median penetrations led to the paramedian or lateral herniation, and 92% of the paramedian penetrations led to lateral herniation through oblique courses. Conclusions. In the cervical spine, most herniated masses penetrate the deep layer of the posterior longitudinal ligament in the middle, where the posterior intervertebral space is widest. Oblique courses to paramedian or lateral herniation are common. Only at C7-T1, where there are no Luschka joints, lateral penetration was observed. The narrow space of the Luschka joint may prevent fragments from penetrating laterally. Preoperative information from the CT discograms on the characteristic courses of the herniation may facilitate the complete removal of herniated mass in anterior decompressive surgery.