A 33 year-old man developed severe low back pain radiating down the left leg. Examination showed an absent left ankle reflex and loss of sensation over the left lateral foot and posterior lateral leg. Straight leg raise on the left caused severe pain radiating down from the buttock to the ankle.

Among spinal disorders, herniated disks are very common. Disks are located between the vertebral bodies. They are composed of a thick annulus fibrosus surrounding an jelly like interior known as the nucleus pulposus. Along the front and back of the vertebral bones and disks are the anterior and posterior longitudinal ligaments, respectively. Thus, disk herniations most often are posterior lateral where they compress the exiting nerve root at that level. Straight posterior disk herniations, although less common, may result in direct spinal cord or cauda equina compression.