MORPHOLOGY OF C5 VENTRAL NERVE ROOTLETS AS PART OF DISSOCIATED MOTOR LOSS OF DELTOID MUSCLE

Study Design. This study analyzed anatomic characteristics of cervical ventral rootlets. After total vertebrectomy, detailed morphology of the ventral rootlets was studied from the anterior. Summary of Background Data. The clinical study showed the predominance of ventral root lesion. There are few studies concerning the morphologic pathogenesis of cervical amyotrophy and detailed cervical ventral rootlet anatomy. Methods. Thirty-six embalmed adult human cadavers were studied. The measurements for the ventral rootlets of C5 to C8 were made as follows: 1) angle between the rootlet and spinal cord, 2) longitudinal width of the ventral rootlet origin, and 3) length of the ventral rootlets. Results. The C5 ventral rootlets were shorter and issued more obtusely from the cervical spinal cord than lower rootlets. The spinal cord segment of the deltoid muscle, indicated by the iongitudinal widths of the C5 and C6 ventral rootlet exists from the spinal cord, were wider than the C7 and C8 segments. Preforaminal anterior compression at the C4-C5 disc level might affect the lower part of the C5 ventral rootlets and upper part of the C6 ventral rootlets. Conclusion. Short C5 ventral rootlets appeared to become taut and easily injured by hemilateral anterior compression. Spinal cord lesion resulting from localized anterior compression at the single disc level might not play as important a role in the pathogenesis of dissociated motor loss of the deltoid muscle because of the wider spinal segments of C5 and C6.