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# C3–C4 nucleus

The nucleus pulposus is the soft, gel-like centre of the [C3-C4](https://durgical.com/en/anatomy/c3-c4/) disc in the neck; it works like a water cushion that spreads the load.

Official name: C3-C4

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## What it is

The soft, gel-like centre (nucleus pulposus) of the C3–C4 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

- A central herniation of the C3–C4 nucleus presses on the [spinal cord](https://durgical.com/en/anatomy/spinal-cord/) rather than a root: hyperreflexia, Hoffmann sign, clumsy hands and an unsteady gait
- A posterolateral fragment still lands on the C4 root, so neck and shoulder-top pain can coexist with cord signs

## Key facts

**Where**
Centre of the C3–C4 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 C4 root

## Relations

**Behind**
Annulus fibrosus and [posterior longitudinal ligament](https://durgical.com/en/anatomy/posterior-longitudinal-ligament/), then the cord at about its C4–C5 segments

**Lateral**
Uncovertebral joints of C4 and the C4 root at the entrance of its foramen

## How to find it

From the front, at about the level of the [hyoid bone](https://durgical.com/en/anatomy/hyoid-bone/) and the upper border of the [thyroid cartilage](https://durgical.com/en/anatomy/thyroid-cartilage/); from behind the cervical spines are too deep to count reliably this high.

## Examination

- Hoffmann sign: flicking the nail of the middle finger makes the thumb and index finger flex; a positive sign points to an upper motor neuron lesion such as cord compression
- Lhermitte sign: an electric feeling down the [spine](https://durgical.com/en/anatomy/region/spine/) or into the limbs when the neck bends forward suggests irritation of the cervical cord

## On imaging

Sagittal T2 MRI shows loss of the bright fluid around the cord at the level of the herniation; a bright spot inside the cord (oedema or myelomalacia) marks cord damage.

## 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

- Sudden neck extension, as in a fall onto the face, in a person with a central herniation or a narrow canal can cause central cord syndrome: arms weaker than legs, hands worst
- In older adults whose lower cervical levels have stiffened, movement shifts upward and C3–C4 becomes a frequent site of cord compression

## Related conditions

- [Degenerative cervical myelopathy](https://durgical.com/en/conditions/degenerative-cervical-myelopathy/)

## Test yourself

Think of the answer, then tap the question to see it.

## What signs does a central herniation of the C3–C4 nucleus cause?

Spinal cord signs rather than a root picture: hyperreflexia, a Hoffmann sign, clumsy hands and an unsteady gait.

## Which root does a posterolateral fragment of the C3–C4 nucleus reach?

The C4 root, giving neck and shoulder-top pain, which can coexist with cord signs.

## Which syndrome can sudden neck extension cause in a person with a central C3–C4 nucleus herniation?

Central cord syndrome: the arms are weaker than the legs and the hands are worst, as after a fall onto the face.

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Educational information, not medical advice. For any symptom, see a health professional.

## Its names

**Official Latin (TA2)**
nucleus pulposus C3-C4 TA2 1686

**Official Spanish (DeCS)**
Núcleo pulposo C3-C4 DeCS D000070614

**English (TA2)**
C3-C4

## Related

- [C3–C4 disc](https://durgical.com/en/anatomy/c3-c4/)
- [C3 vertebra](https://durgical.com/en/anatomy/cervical-vertebrae/)
- [C4 vertebra](https://durgical.com/en/anatomy/c4/)

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/).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/anatomy/c3-c4-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/c3-c4-spine-and-pelvis/