Angulated Course of Spinal Nerve Roots

CCORDING to the classic description found in standard books of anatomy and other medical literature, 9,~~ the roots of the spinal nerves in the adult adjust to a more or less characteristic pattern for each spinal region. To reach their corresponding intervertebral or sacral foraminae, courses of the upper spinal nerves run horizontally; the lower nerves slant more obliquely downward and laterally; and the lowest nerves, below the first lumbar, run nearly straight downward in the vertebral canal forming the cauda equina. No changes in the direction of the nerves are described between the intradural and extradural portions of their course. During many dissections, we have found that the description above is not always accurate. In the majority of cases, a variable number of spinal nerve roots, generally the lower cervical and the upper thoracic one3, followed an angulated course. In these cases, the nerves ran downward in the dural sac, but after perforating the dura mater, altered their course and proceeded upwards. We have found very few other reports ~,~,~ in the literature describing this variation.