The anatomic relation among the nerve roots, intervertebral foramina, and intervertebral discs of the cervical spine

Study Design. An anatomic study of the cervical intervertebral foramina, ne rve roots, and intradural rootlets performed using a surgical microscope. Objectives. To investigate the anatomy of cervical root compression, and to obtain the anatomic findings related to cervical foraminotomy for the trea tment of cervical radiculopathy. Summary of Background Data. Cervical foraminotomy is a procedure performed frequently for the management of cervical radiculopathy. However, anatomic studies of cervical foraminotomy have not been fully elucidated. Methods. In this study, 18 cadavers were obtained for the study of the cerv ical spine. All the soft tissues were dissected from the cervical spine. Th ereafter, laminectomy and facetectomy were performed on C4 through T1 using a surgical microscope. The nerve roots and surrounding anatomic structures , including intervertebral discs and foramina, were exposed. In addition, t he intradural rootlets and their intersegmental connections were observed. Results. The shape of the intervertebral foramina approximated a funnel, th e entrance zone being the most narrow part and the root sleeves conical, wi th their takeoff points from the central dural sac being the largest part. Therefore, compression of the nerve roots occurred at the entrance zone of the intervertebral foramina. Anteriorly, compression of the nerve roots was caused by protruding discs and osteophytes of the uncovertebral region, wh ereas the superior articular process, the ligamentum flavum, and the perira dicular fibrous tissues affected the nerve posteriorly. The C5 nerve roots were found to exit over the middle aspect of the intervertebral disc, where as the C6 and C7 nerve roots were found to traverse the proximal part of th e disc. The C8 nerve roots had little overlap with the C7-T1 disc in the in tervertebral foramen. The C6 and C7 rootlets passed two disc levels in the dural sac. Also, a high incidence of the intradural connections between the dorsal rootlets of C5, C6, and C7 segments was found. Conclusions. This study demonstrated the anatomy of the nerve roots, rootle ts, and intervertebral foramina, and may aid in understanding the pathology of cervical radiculopathy. The presence of intradural connections between dorsal nerve roots and the relation between the course of the nerve root an d the intervertebral disc may explain the clinical variation of symptoms re sulting from-nerve root compression in the cervical spine. To perform cervi cal foraminotomy for cervical radiculopathy, it is necessary to understand the detailed anatomy of the intervertebral foramina thoroughly.