Which nerve structures provide innervation to the disc's outer one-third?

Which nerve structures provide innervation to the disc's outer one-third?

• A. Spinal accessory nerve
• B. Recurrent meningeal nerve and grey ramus communicans
• C. Dorsal ramus
• D. Intercostal nerve

Answer: (B)

The outer third of the intervertebral disc is innervated by a branch that re-enters the vertebral canal to reach the disc: the sinuvertebral (recurrent meningeal) nerve. This nerve supplies the posterior annulus fibrosus and the posterior longitudinal ligament with sensory fibers, and it travels with sympathetic fibers via the grey rami communicantes to reach the disc region. The combination of the recurrent meningeal/sinuvertebral nerve and the grey ramus communicans best explains innervation of the disc’s outer third. Other nerves listed don’t supply the disc in this way: the spinal accessory nerve serves neck muscles, the dorsal ramus mainly supplies paraspinal muscles and overlying skin, and intercostal nerves map to the thoracic wall rather than the disc itself.

The outer third of the intervertebral disc is innervated by a branch that re-enters the vertebral canal to reach the disc: the sinuvertebral (recurrent meningeal) nerve. This nerve supplies the posterior annulus fibrosus and the posterior longitudinal ligament with sensory fibers, and it travels with sympathetic fibers via the grey rami communicantes to reach the disc region. The combination of the recurrent meningeal/sinuvertebral nerve and the grey ramus communicans best explains innervation of the disc’s outer third.

Other nerves listed don’t supply the disc in this way: the spinal accessory nerve serves neck muscles, the dorsal ramus mainly supplies paraspinal muscles and overlying skin, and intercostal nerves map to the thoracic wall rather than the disc itself.