This is the rind-like outer surface of discs within the spine. The annulus contains the nucleus pulposus. Wear and tear on the annulus can result in protrusion or bulging of the nucleus. Nucleus pulposus can herniate through a tear in the annulus resulting in a herniated disc (also known as a disc herniation or herniated nucleus pulposus or HNP). Bulging, protrusion or herniation of disc material can compress nerve roots or the spinal cord resulting in neurologic compromise (pain, numbness or weakness). Neurologic compromise (pain, numbness or weakness) can be caused by mechanical compression or inflammation of the neural structures (nerve roots or the spinal cord).