Disc herniations are a condition where the soft “jellylike” center of a spinal disc known as the nucleus pulposus impedes on the spinal cord. The role of the disc is to support the spine by acting as a “shock-absorbing” cushion. Disc herniations are categorized into four types based on the severity of the actual herniation: Bulging, protrusion, extrusion, and sequestration.
Bulging: Extension of the disc margin beyond the margins of the adjacent vertebral endplates.
Protrusion: The posterior longitudinal ligament remains intact, but the nucleus pulposus impinges on the annulus fibrosus.
Extrusion: The nuclear material emerges through the annular fibers, but the posterior longitudinal ligament remains intact.
Sequestration: The nuclear material emerges through the annular fibers, and the posterior longitudinal ligament is disrupted. A portion of the nucleus pulposus has protruded into the epidural space.