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# Dorsal root ganglia

The dorsal root ganglia are small swellings on the sensory nerve roots, in the side openings of the [spine](https://durgical.com/en/anatomy/region/spine/); they relay all body sensation.

Official name: Spinal ganglion

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## What it is

Small swellings on the sensory roots, in each side opening of the spine, holding the cell bodies of the sensory nerves.

## What it does

Relay all sensation from the body to the cord. Very sensitive to pressure: one reason a pinched root hurts so much.

## Key points

- A lesion proximal to the ganglion (root avulsion) leaves the sensory nerve action potential normal in a numb limb; a distal lesion abolishes it: the key test of preganglionic vs postganglionic injury
- Varicella-zoster virus lies dormant here and reactivates as shingles in that dermatome, most often a thoracic one
- Lying in the foramen, it is pinched by foraminal stenosis and far-lateral disc herniations, which cause especially severe radicular pain

## Key facts

**Where**
On each dorsal root in the intervertebral foramen, just outside the dural sac (sacral ganglia inside the sacral canal)

**Function**
Cell bodies of pseudounipolar primary sensory neurons; no synapses

## Relations

**Above**
The pedicle of the vertebra above, under which it sits in the foramen

**In front**
The disc and vertebral body (in the neck, the uncovertebral joint); the ventral root runs in front of it

**Behind**
The facet joint, formed here by the superior articular process of the vertebra below

**Lateral**
Just beyond it the dorsal and ventral roots join into the spinal nerve, which splits into dorsal and ventral rami; in the neck the [vertebral artery](https://durgical.com/en/anatomy/vertebral-artery/) lies in front of the nerve

## How to find it

It cannot be felt. Most lie in the intervertebral foramen, just under the pedicle and outside the dural sac; the exceptions are the upper two cervical ganglia, which sit beside the arches of the [atlas](https://durgical.com/en/anatomy/atlas/) and [axis](https://durgical.com/en/anatomy/axis/), and the sacral and coccygeal ones, which stay inside the sacral canal.

## On imaging

On MRI it is an oval swelling in the foramen that normally enhances with contrast (it has no blood-nerve barrier), which should not be mistaken for a tumour. Perineural (Tarlov) cysts on the sacral roots are common incidental findings.

## Common problems

- Cervical radiculopathy: a disc or bone spur pinches a root, causing pain, numbness or weakness down the arm in that root's pattern.

## How it is diagnosed

Exam of strength, reflexes and feeling in the arm (each root has its own pattern); MRI; sometimes nerve tests (EMG).

## Treatment

- Most improve with time, physical therapy, medicine and sometimes an injection.
- Lasting pain or weakness: surgery to free the root, such as ACDF or a foraminotomy.

## Clinical notes

- Postherpetic neuralgia: pain that persists after shingles has healed, from damage in the ganglion and its nerve
- Sensory neuronopathy (ganglionopathy) from Sjögren syndrome, paraneoplastic disease or toxins: patchy, non-length-dependent sensory loss and sensory ataxia
- Target of transforaminal injections and pulsed radiofrequency for chronic radicular pain

## Development

The ganglia come from neural crest cells, like the autonomic ganglia, which is why they lie outside the neural tube.

## Related conditions

- [Herpes zoster (shingles)](https://durgical.com/en/conditions/herpes-zoster/)
- [Guillain-Barré syndrome](https://durgical.com/en/conditions/guillain-barre-syndrome/)

## Test yourself

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

## Where are the dorsal root ganglia, and what do they contain?

On each dorsal root in the intervertebral foramen, just outside the dural sac; they hold the cell bodies of pseudounipolar sensory neurons, with no synapses.

## How do sensory nerve action potentials separate a root avulsion from a more distal lesion?

A lesion proximal to the dorsal root ganglion leaves the sensory potential normal in a numb limb; a distal lesion abolishes it.

## Which virus lies dormant in the dorsal root ganglia?

Varicella-zoster virus, which reactivates as shingles in that dermatome, most often a thoracic one.

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

## Its names

**Official Latin (TA2)**
ganglion spinale TA2 6167

**Official Spanish (DeCS)**
Ganglios espinales DeCS D005727

**English (TA2)**
Spinal ganglion

**Also called**
sensory ganglion of spinal nerve · dorsal root ganglion · Ganglia, Spinal · ganglion spinale sensoriale

## Related

- [Neck nerve roots](https://durgical.com/en/anatomy/anterior-root-of-spinal-nerve/)

Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=5868&filter=ths_termall&q=Ganglios%20Espinales); [Neuroanatomy, Spinal Nerves](https://www.ncbi.nlm.nih.gov/books/NBK542218/).

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Source: https://durgical.com/en/anatomy/spinal-ganglion/
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