Routinely, with either cervical or lumbar myelography, there is symmetrical filling of the nerve root sleeves without evidence of nerve root displacement or nerve root sleeve truncation. The size and direction of the spinal roots vary at different levels. The largest roots are the lower lumbar and upper sacral roots, which innervate the lower extremities. Accordingly, the roots of the lower four cervical and
first thoracic nerves are also large, owing to their upper extremity innervation. The upper cervical and remaining thoracic nerve roots are rather small in comparison, and the lower sacral and coccygeal nerve roots are the smallest. Discrepancies in length and direction of spinal nerve roots is secondary to the spinal cord being much shorter than the vertebral canal. In the cervical region, the relatively short nerve root traverses the lower portion of its respective neural canal in a horizontal direction. The thoracic nerve roots are directed obliquely downward, with the length and degree of obliquity increasing from the upper to the lower thoracic levels. Because the spinal cord ends at approximately L1, the lumbar, sacral, and coccygeal nerve roots descend in a nearly parallel course, with the length of the roots increasing successively from above downward. This group of nerve roots below the level of termination of the cord is termed the cauda equina. The thecal sac should have a smooth contour without evidence of narrowing or mass effect from extradural abnormalities. There should be smooth tapering of the distal thecal sac at a variable distance below the L5-S1 disc space to a smooth "pencil point" appearance. The silhouette of the cervical and thoracic cord as well as the appearance and position of the conus should be closely scrutinized for intramedullary expansile lesions.
Was this article helpful?
This guide will help millions of people understand this condition so that they can take control of their lives and make informed decisions. The ebook covers information on a vast number of different types of neuropathy. In addition, it will be a useful resource for their families, caregivers, and health care providers.