[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anatomy](https://durgical.com/en/anatomy/) › [Spine](https://durgical.com/en/anatomy/region/spine/) › C4–C5 nucleus [Joints and ligaments](https://durgical.com/en/anatomy/system/joints-and-ligaments/) · [Spine](https://durgical.com/en/anatomy/region/spine/) # C4–C5 nucleus The nucleus pulposus is the soft, gel-like centre of the [C4-C5](https://durgical.com/en/anatomy/c4-c5/) disc in the neck; it works like a water cushion that spreads the load. Official name: C4-C5 [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=spine&select=nucleus_c4_c5&side=r) Opens in the Durgical app, no sign-up needed. ## What it is The soft, gel-like centre (nucleus pulposus) of the C4–C5 disc. ## What it does Works like a water cushion: it turns pressure from above into outward push on the fibre ring, spreading the load. It is under the most pressure when you bend forward and lift. ## Key points - Herniation types: protrusion (the base of the displaced nucleus is wider than its tip), extrusion (the tip is wider than the base, or the material has migrated), sequestration (a free fragment) - A contained herniation stays under the outer annulus and the posterior longitudinal ligament; an uncontained one breaks through them ## Key facts **Where** Centre of the C4–C5 disc, slightly toward the back, inside the annulus fibrosus **Function** Notochord-derived gel (about 70–90% water, proteoglycans); turns axial load into annulus tension; herniates posterolaterally toward the C5 root ## Relations **Behind** Annulus fibrosus and [posterior longitudinal ligament](https://durgical.com/en/anatomy/posterior-longitudinal-ligament/), then the [spinal cord](https://durgical.com/en/anatomy/spinal-cord/) **Lateral** Uncovertebral joints of C5, the C5 root entering its foramen, and the [vertebral artery](https://durgical.com/en/anatomy/vertebral-artery/) beyond ## How to find it From the front, behind the [thyroid cartilage](https://durgical.com/en/anatomy/thyroid-cartilage/) (about C4–C5); from behind, about two spinous processes above the [vertebra prominens](https://durgical.com/en/anatomy/vertebra-prominens/). ## Examination - C5 root: weak shoulder abduction (deltoid) and elbow flexion, a numb patch over the outer upper arm, and a reduced biceps reflex (C5–C6) - Spurling test: the neck is extended and turned toward the painful side with gentle downward pressure on the head; reproduced arm pain suggests root compression in the foramen ## On imaging Axial T2 MRI shows where the C4–C5 fragment sits: centrally against the cord, or posterolaterally at the entrance of the C5 foramen. ## Common problems - Squeezes out through a tear in the ring (herniation), usually backward and to one side, toward a nerve root. - Loses water with age, so the disc gets thinner and stiffer. ## How it is diagnosed On MRI a healthy nucleus is bright on T2 images; a worn one turns dark ('black disc'). ## Treatment - In a microdiscectomy only the loose piece that has pushed out is removed; most of the disc stays. ## Clinical notes - The adult nucleus has no blood vessels and is fed by diffusion through the [endplates](https://durgical.com/en/anatomy/vertebral-endplates/), so a torn annulus heals poorly and the nucleus slowly loses water - An extruded or sequestered fragment more often shrinks on its own than a protrusion does ## Development In infancy the nucleus is rich in large notochordal cells and water. During childhood these cells are replaced by smaller cartilage-like cells, and the water content keeps falling with age, the first step of disc degeneration. ## Related conditions - [Cervical radiculopathy](https://durgical.com/en/conditions/cervical-radiculopathy/) ## Test yourself Think of the answer, then tap the question to see it. ## How are protrusion, extrusion and sequestration of the C4–C5 nucleus defined? Protrusion: the base of the displaced nucleus is wider than its tip. Extrusion: the tip is wider than the base, or the material has migrated. Sequestration: a free fragment. ## What makes a herniation of the C4–C5 nucleus «contained»? It stays under the outer annulus fibrosus and the posterior longitudinal ligament; an uncontained one breaks through them. ## Why does a torn annulus around the C4–C5 nucleus heal poorly? The adult nucleus has no blood vessels and is fed by diffusion through the endplates, so it slowly loses water. ## Which type of C4–C5 nucleus herniation more often shrinks on its own? An extruded or sequestered fragment, more often than a protrusion. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/anatomy/c4-c5-spine-and-pelvis/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** nucleus pulposus C4-C5 TA2 1686 **Official Spanish (DeCS)** Núcleo pulposo C4-C5 DeCS D000070614 **English (TA2)** C4-C5 ## Related - [C4–C5 disc](https://durgical.com/en/anatomy/c4-c5/) - [C4 vertebra](https://durgical.com/en/anatomy/c4/) - [C5 vertebra](https://durgical.com/en/anatomy/c5/) Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=56248&filter=ths_termall&q=N%C3%BAcleo%20Pulposo); [Anatomy, Back, Nucleus Pulposus](https://www.ncbi.nlm.nih.gov/books/NBK535373/); [Anatomy, Back, Intervertebral Discs](https://www.ncbi.nlm.nih.gov/books/NBK470583/); [7.3 The Vertebral Column](https://openstax.org/books/anatomy-and-physiology-2e/pages/7-3-the-vertebral-column) (OpenStax (Rice University), 2022) · adapted, [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/); [7.5 Embryonic Development of the Axial Skeleton](https://openstax.org/books/anatomy-and-physiology-2e/pages/7-5-embryonic-development-of-the-axial-skeleton) (OpenStax (Rice University), 2022) · adapted, [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/anatomy/c4-c5-spine-and-pelvis/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/c4-c5-spine-and-pelvis/