Spinal ganglion

At a glance

English

Spinal ganglion

Latin (TA2)

Ganglion spinale

System

Nerve

Region

Whole body

Side

Paired, left and right

About the spinal ganglion

A spinal ganglion, also called a dorsal or posterior root ganglion, is an oval swelling on the posterior (sensory) root of a spinal nerve. There is one on each side at almost every spinal level. Each lies in or close to the intervertebral foramen, just inside the point where the posterior and anterior roots join to form the spinal nerve. The ganglia of the upper cervical nerves lie on the vertebral arches, and those of the sacral nerves sit inside the sacral canal. The first cervical ganglion may be small or absent.

The ganglion is packed with the cell bodies of first-order sensory neurons. These cells are pseudounipolar: a single stem leaves the cell body and divides in a T into a peripheral branch, running out in the spinal nerve to the skin, muscles, joints or viscera, and a central branch, entering the spinal cord through the posterior root. The two branches work as one continuous axon, and an impulse can pass from the periphery to the cord without involving the cell body. There are no synapses in the ganglion. Each cell body is wrapped by satellite cells, and the whole ganglion is enclosed in a capsule continuous with the dura and with the sheath of the nerve.

The peripheral endings take many forms. Some are bare nerve endings that respond to pain, heat or chemicals, while others are enclosed in end organs such as Meissner corpuscles, tuned to light stroking, or Pacinian corpuscles, which respond to vibration. Large cells give fast myelinated fibres for touch and position sense; small cells give thin fibres for pain and temperature. In development the ganglia come from the neural crest, not from the neural tube.

Because the ganglion sits in the narrow intervertebral foramen, it can be squeezed by a disc prolapse or bony narrowing, producing pain and tingling along the dermatome of that nerve. Varicella-zoster virus can lie dormant in these cells and later reawaken as shingles, a painful rash in one dermatome.

Course and supply

Arises from

Lies on the posterior root of a spinal nerve, formed by the cell bodies of first-order sensory neurons.

Ends in

Its central branches enter the spinal cord through the posterior root; its peripheral branches run out in the spinal nerve to their receptors.

Supplies

Holds the sensory neurons for touch, pressure, vibration, position, pain and temperature from the body wall, limbs and viscera of its segment.

Blood supply

Supplied by spinal branches of segmental arteries, the radicular arteries, entering through the intervertebral foramen.