The cauda equina syndrome

Abstract

Cauda equina refers to that part of the nervous system which is situated below the level of the conus medullaris, within the spinal canal. It consists of both sensory and motor nerve bundles.1 The length of the spinal cord is shorter than the vertebral canal. As a consequence of the relative inequality in the rates of growth of the spinal cord and the vertebral column, the nerve roots, which in the early embryo passed transversally outward to reach their respective intervertebral foramina, become more and more oblique in direction from above downward during normal development, so that the lumbar and sacral nerves descend almost vertically to reach their point of exit from the vertebral canal. From the appearance of these nerves at their attachment to the spinal cord, and from their great length, they are collectively named the cauda equina.2 Injury to the nerves of the cauda equina can result in the so-called cauda equina syndrome (CES), which refers to the simultaneous compression of multiple lumbosacral nerve roots below the level of the conus medullaris. This is typically characterized by low back pain, sciatalgia, saddle and perineal hypoesthesia or anesthesia, decreased anal tone, absent ankle, knee, or bulbocavernosus reflexes, variable lower extremity motor and sensory loss, as well as bowel and bladder dysfunction.2 Mixter and Barr are thought to be the first to report this clinical syndrome, in 1934.3-5Diagnosis of a cauda equina lesion may be complicated and require neuroradiologic imaging together with bladder, bowel, sexual, and somatic function tests. Management may be difficult and require prolonged intensive and longterm rehabilitation.2,6Neuroanatomy The relationship between the terminal part of the spinal cord, the conus terminalis, and the vertebral column changes during intrauterine development, in the neonate, in infancy, and in the adult. This is because the vertebral column grows more rapidly in the longitudinal direction than does the spinal cord.7,8 In the third month ofintrauterine life, the spinal cord fills the whole length of the vertebral canal. In neonates, the spinal cord terminates at the lumbosacral junction.7 During infancy and early childhood, the spinal cord terminates between the first and third lumbar vertebrae,7,8 whereas in adults, it may terminate at a level anywhere from the T12 vertebral body to the L2 and L3 intervertebral space.1,2,7-9 Arai et al studied 602 patients aged between 8 months and 84 years and found the location of the conus medullaris at the middle onethird of L110 (Figure 27.1).