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# T11–T12 nucleus

The nucleus pulposus is the soft, gel-like centre of the [T11-T12](https://durgical.com/en/anatomy/t11-t12/) disc in the mid-back; it works like a water cushion that spreads the load.

Official name: T11-T12

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## What it is

The soft, gel-like centre (nucleus pulposus) of the T11–T12 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

- One of the most frequently herniated thoracic nuclei, at the junction where the rib cage stops splinting the [spine](https://durgical.com/en/anatomy/region/spine/)

## Key facts

**Where**
Centre of the T11–T12 disc, slightly toward the back, inside the annulus fibrosus

**Function**
Notochord-derived gel (about 70–90% water, proteoglycans); turns axial load into annulus tension; small in thin thoracic discs, herniation rare

## Relations

**Behind**
Back of the annulus fibrosus and the [posterior longitudinal ligament](https://durgical.com/en/anatomy/posterior-longitudinal-ligament/), then the lower [spinal cord](https://durgical.com/en/anatomy/spinal-cord/) near the [conus medullaris](https://durgical.com/en/anatomy/conus-medullaris/)

## How to find it

Found on imaging, not by touch. The level is fixed by counting down from C2 on a whole-spine sagittal scout and checking it against the 12th rib, because wrong-level surgery is a known risk in the thoracic spine.

## Examination

- Ankle jerks and toe strength, with perianal sensation and the anal reflex, test the lowest cord segments, which lie just behind and below this level

## On imaging

Before surgery at this level, CT or MR angiography may be used to locate the [artery of Adamkiewicz](https://durgical.com/en/anatomy/great-radicular-artery/), which often enters the canal nearby.

## 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

- Epiconus syndrome: compression just above the conus (roughly the L4–S2 segments, texts vary) gives foot and ankle weakness with mixed reflexes, sometimes with early bladder trouble
- Thoracic herniations are far less common than cervical or lumbar ones, and many are incidental MRI findings; symptomatic fragments are often calcified, which makes removal harder
- These herniations are removed from the side or the front (transpedicular, costotransversectomy, thoracoscopic or open transthoracic routes); a plain laminectomy would need the cord to be retracted and carries a high risk of worsening the deficit

## Development

The nucleus is what is left of the notochord: the notochord vanishes from the growing vertebral bodies but survives between them, where it helps build each disc.

## Test yourself

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

## Why is the T11–T12 nucleus one of the most frequently herniated thoracic nuclei?

It sits at the junction where the rib cage stops splinting the spine.

## Which artery may be located with CT or MR angiography before surgery on the T11–T12 nucleus?

The artery of Adamkiewicz, which often enters the canal near this level.

## Which part of the spinal cord lies behind the T11–T12 nucleus pulposus?

The lower cord near the conus medullaris, behind the annulus fibrosus and the posterior longitudinal ligament.

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

## Its names

**Official Latin (TA2)**
nucleus pulposus T11-T12 TA2 1686

**Official Spanish (DeCS)**
Núcleo pulposo T11-T12 DeCS D000070614

**English (TA2)**
T11-T12

## Related

- [T11–T12 disc](https://durgical.com/en/anatomy/t11-t12/)
- [T11 vertebra](https://durgical.com/en/anatomy/t11/)
- [T12 vertebra](https://durgical.com/en/anatomy/t12/)

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/).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/anatomy/t11-t12-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/t11-t12-spine-and-pelvis/