C5–C6 nucleus !
The nucleus pulposus is the soft, gel-like centre of the C5-C6 disc in the neck; it works like a water cushion that spreads the load.
Official name: C5-C6
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What it is
The soft, gel-like centre (nucleus pulposus) of the C5–C6 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 C5–C6 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 C6 root
Relations
- Behind
- Annulus fibrosus and posterior longitudinal ligament, then the spinal cord
- Lateral
- Uncovertebral joints of C6, whose spurs narrow the C6 foramen, and the vertebral artery, which usually enters the transverse foramen of C6
How to find it
From the front, just above the cricoid cartilage (C6), the usual target of the transverse skin crease used for anterior cervical surgery at this level.
Examination
- C6 root: weak wrist extension and elbow flexion, numb thumb and index finger, reduced brachioradialis (and biceps) reflex
- Shoulder abduction relief sign: resting the hand on top of the head eases the arm pain, which supports a cervical root cause
On imaging
On sagittal T2 MRI a healthy nucleus is bright; with degeneration it greys and then darkens and the disc thins. The Pfirrmann scale (grades I to V) scores this change.
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
- ACDF removes the whole nucleus and fuses the level; a disc replacement removes it too but keeps movement at C5–C6
- A posterolateral C5–C6 fragment numbs the thumb and index finger, which can be mistaken for carpal tunnel syndrome; weak wrist extension and a reduced brachioradialis reflex point to the C6 root
Development
In Klippel–Feil syndrome two or more cervical vertebrae fail to separate, so no proper disc forms between them. The discs next to the fused block take extra load and tend to degenerate early.
Related conditions
Test yourself
Think of the answer, then tap the question to see it.
What is the first step of cervical spondylosis at the C5–C6 level?
Degeneration of the C5–C6 nucleus: it loses water and height, the annulus bulges, and the uncovertebral joints and endplates grow spurs.
How does a disc bulge differ from a herniation of the C5–C6 nucleus?
A bulge involves a large part of the disc rim (more than a quarter); a herniation is a focal displacement of less than a quarter.
How does degeneration of the C5–C6 nucleus look on sagittal T2 MRI?
A healthy nucleus is bright; with degeneration it greys, then darkens, and the disc thins. The Pfirrmann scale (grades I to V) scores this change.
How do ACDF and disc replacement differ in handling the C5–C6 nucleus?
Both remove the whole nucleus; ACDF fuses the level, while a disc replacement keeps movement at C5–C6.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- nucleus pulposus C5-C6 TA2 1686
- Official Spanish (DeCS)
- Núcleo pulposo C5-C6 DeCS D000070614
- English (TA2)
- C5-C6
Related
Sources: Terminologia Anatomica (TA2); DeCS; Anatomy, Back, Nucleus Pulposus; Anatomy, Back, Intervertebral Discs.
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Representative model, for educational purposes only.
