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# Red nucleus

The red nucleus is a round cluster of cells in the midbrain; it relays movement signals between the [cerebellum](https://durgical.com/en/anatomy/anterior-quadrangular-lobule/) and the brain's cortex.

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## What it is

A round nucleus in the midbrain.

## What it does

Relays motor signals between the cerebellum and the cortex.

## Key points

- Benedikt syndrome: a tegmental [midbrain](https://durgical.com/en/anatomy/midbrain/) lesion through the red nucleus and oculomotor fibres causes an oculomotor palsy on the same side and tremor or involuntary movements of the opposite limbs
- The rubrospinal tract crosses at once (ventral tegmental decussation), runs in the lateral column of the [spinal cord](https://durgical.com/en/anatomy/spinal-cord/) and favours flexor tone in the arm; it is small in humans
- Lesion above the red nucleus: decorticate posture (arms flexed, legs extended); below it: decerebrate posture (arms and legs extended), the worse sign
- Guillain–Mollaret triangle: dentate nucleus, red nucleus and inferior olivary nucleus; a lesion causes palatal tremor

## Key facts

**Where**
Midbrain tegmentum, at the level of the superior colliculus

**Blood supply**
Paramedian branches of the [posterior cerebral artery](https://durgical.com/en/anatomy/posterior-cerebral-artery/)

**Function**
Motor relay between the cerebellum (dentate nucleus) and the cortex; gives the rubrospinal tract

## Relations

**In front**
[Substantia nigra](https://durgical.com/en/anatomy/substantia-nigra/) (anterolaterally) and the cerebral peduncle

**Behind**
Tegmentum and the periaqueductal grey around the [cerebral aqueduct](https://durgical.com/en/anatomy/aqueduct-of-midbrain/), at the level of the superior colliculi

**Medial**
[Oculomotor nerve](https://durgical.com/en/anatomy/oculomotor-nerve/) fibres running forward through and beside it toward the interpeduncular fossa

**Lateral**
Medial lemniscus

**Course**
Input: crossed fibres of the [superior cerebellar peduncle](https://durgical.com/en/anatomy/superior-cerebellar-peduncle/) from the opposite dentate nucleus, and the [motor cortex](https://durgical.com/en/anatomy/precentral-gyrus/). Output: rubrospinal tract (crossed) and the central tegmental tract to the inferior olivary nucleus

## How to find it

On an axial cut at the level of the superior colliculi it is a round mass in the tegmentum, behind and medial to the substantia nigra, crossed by oculomotor nerve fibres on their way to the interpeduncular fossa. On T2-weighted MRI it looks dark from its iron content.

## On imaging

Rich in iron, so on T2 and susceptibility MRI it looks dark (hypointense), like the substantia nigra; the iron also gives fresh tissue its pinkish colour.

## Clinical notes

- Holmes (rubral) tremor: a slow, coarse tremor present at rest, on posture and on movement, after midbrain lesions that interrupt the cerebellar outflow near the red nucleus
- Claude syndrome: a slightly more dorsal tegmental lesion gives an oculomotor palsy with opposite-side cerebellar ataxia

## Memory aid

deCORticate: the hands are drawn toward the 'cor' (heart); decErebrate: everything is Extended.

## Related conditions

- [Parkinson disease](https://durgical.com/en/conditions/parkinson-disease/)

## Test yourself

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

## What is Benedikt syndrome?

A tegmental midbrain lesion through the red nucleus and oculomotor fibres: oculomotor palsy on the same side and tremor or involuntary movements of the opposite limbs.

## How do decorticate and decerebrate postures relate to the red nucleus?

Lesion above the red nucleus: decorticate (arms flexed, legs extended); below it: decerebrate (all limbs extended), the worse sign.

## Which three structures form the Guillain–Mollaret triangle, and what does a lesion cause?

Dentate nucleus, red nucleus and inferior olivary nucleus; a lesion causes palatal tremor.

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

## Its names

**Official Latin (TA2)**
nucleus ruber TA2 5898

**Official Spanish (DeCS)**
Núcleo Rojo DeCS D012012

**English (TA2)**
Red nucleus

## Related

- [Midbrain](https://durgical.com/en/anatomy/midbrain/)

Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=22654&filter=ths_termall&q=Red%20Nucleus); [Neuroanatomy, Red Nucleus](https://www.ncbi.nlm.nih.gov/books/NBK551628/).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/anatomy/red-nucleus/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/red-nucleus/