Science today isn't the same as the science 2000 years ago was but some principles remain the same. The human knowledge constantly grows but with more knowledge there comes even more mysteries and unsolved questions, so science is always going forward.
Causes. The most common cause of a cervical herniated nucleus pulposus is gradual degeneration of the disc, attenuation (weakening) of the posterior annulus fibrosis, and subsequent protrusion of the nucleus pulposus into the spinal canal causing compression of the nerve root.
A spinal disc herniation commonly called a slipped disc, can happen when the gel-like material of the nucleus pulposus is forced against a weakness in the surrounding anulus fibrosus, putting pressure on the nearby nerve. This can give the symptoms of sciatica if it impinges on the roots of the sciatic nerve.