Between each vertebral body there is an intervertebral disc. The disc allows to cushion the vertebral bodies, as well as allows movement. The intervertebral disc is made up annulus fibrosus, which surrounds a central gel-like material called the nucleus pulposus. Due to injury or due to aging, the nucleus pulposus may tend to extrude into the fissures of the annulus fibrosus. When this happens, the patient may present with back pain, but most of the patients are asymptomatic.
When the fissures propagate, the nucleus pulposus may protrude out from the back of the annulus fibrosus where it starts compressing on the nerve roots or the spinal cord. When this happens, the patient starts to have particular pain going down the arm or the leg or tingling or numbness. These patients may also have weakness or involvement of the bladder.