✓ An epispinal system of motor axons virtually covers the ventral and lateral funiculi of the human conus medullaris between the L-2 and S-2 levels. These nerve fibers apparently arise from motor cells of the ventral horn nuclei and join spinal nerve roots caudal to their level of origin. In all observed spinal cords, many of these axons converged at the cord surface and formed an irregular group of ectopic rootlets that could be visually traced to join conventional spinal nerve roots at one to several segments inferior to their original segmental level; occasional rootlets joined a dorsal nerve root. As almost all previous reports of nerve root interconnections involved only the dorsal roots and have been cited to explain a lack of an absolute segmental sensory nerve distribution, it is believed that these intersegmental motor fibers may similarly explain a more diffuse efferent distribution than has previously been suspected.
Wesley W. Parke and Ryo Watanabe
Ryo Watanabe and Wesley W. Parke
✓ During a study of the intrinsic vasculature of the lumbosacral spinal nerve roots in cadavers, a typical case of spinal stenosis was encountered. A review of the antemortem anamnesis revealed that this patient had had an intermittent claudication of the cauda equina. Investigation of the concomitant vascular and histopathological alterations of the affected nerve roots suggested that the claudication may have resulted from ectopic nerve impulse discharges elicited by rapid changes in the blood supply following exertion. The unexpectedly slight apparent neural deficit relative to observed root damage may be attributed to a neuronal plasticity within the spinal cord that permitted functional compensations to develop during the slow acquisition of the chronic nerve root pathology.