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# T1–T2 nucleus

The nucleus pulposus is the soft, gel-like centre of the [T1-T2](https://durgical.com/en/anatomy/t1-t2/) disc in the mid-back; it works like a water cushion that spreads the load.

Official name: T1-T2

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## What it is

The soft, gel-like centre (nucleus pulposus) of the T1–T2 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 fragment escaping backward and to the side reaches the T1 root, the only thoracic root that supplies the hand

## Key facts

**Where**
Centre of the T1–T2 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**
Thin back of the annulus fibrosus and the [posterior longitudinal ligament](https://durgical.com/en/anatomy/posterior-longitudinal-ligament/), then the [spinal cord](https://durgical.com/en/anatomy/spinal-cord/); the T1 root lies behind and to the side

## Examination

- T1 root: finger spreading against resistance (interossei) is weak and the inner arm near the elbow is numb

## On imaging

Axial T2 MRI through T1–T2 shows whether a fragment has moved into the foramen toward the T1 root; plain films are of little help, as the shoulders overlap this level.

## 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

- A T1 root lesion may come with Horner syndrome on the same side (small pupil, drooping lid), since sympathetic fibres for the head leave the cord through T1
- An apical lung (Pancoast) tumour produces the same hand weakness and Horner picture and is ruled out on imaging

## Test yourself

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

## Which root can a posterolateral fragment of the T1–T2 nucleus reach, and what is special about it?

The T1 root, the only thoracic root that supplies the hand.

## Which imaging shows a T1–T2 nucleus fragment moving toward the T1 root?

Axial T2 MRI through T1–T2; plain films help little, as the shoulders overlap this level.

## What is the T1–T2 nucleus pulposus made of?

A notochord-derived gel, about 70–90% water held by proteoglycans.

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

## Its names

**Official Latin (TA2)**
nucleus pulposus T1-T2 TA2 1686

**Official Spanish (DeCS)**
Núcleo pulposo T1-T2 DeCS D000070614

**English (TA2)**
T1-T2

## Related

- [T1–T2 disc](https://durgical.com/en/anatomy/t1-t2/)
- [T1 vertebra](https://durgical.com/en/anatomy/t1/)
- [T2 vertebra](https://durgical.com/en/anatomy/t2/)

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/).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/anatomy/t1-t2-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/t1-t2-spine-and-pelvis/