C3–C4 nucleus !
The nucleus pulposus is the soft, gel-like centre of the 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 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, 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 and the upper border of the 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 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
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.
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
Sources: Terminologia Anatomica (TA2); DeCS; Anatomy, Back, Nucleus Pulposus; Anatomy, Back, Intervertebral Discs.
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Representative model, for educational purposes only.
