The pelvic portion of each

sympathetic trunk The sympathetic trunks (sympathetic chain, gangliated cord) are a paired bundle of nerve fibers that run from the base of the skull to the coccyx. They are a major component of the sympathetic nervous system. Structure The sympathetic trunk lies j ...

is situated in front of the sacrum, medial to the

anterior sacral foramina The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30. The sacrum situates at the upper, back part o ...

. It consists of four or five small

sacral ganglia The sacral ganglia are paravertebral ganglia of the sympathetic trunk.:39 As the sympathetic trunk heads inferiorly down the sacrum, it turns medially. There are generally four or five sacral ganglia. In addition to gray rami communicantes, the gan ...

, connected together by interganglionic cords, and continuous above with the abdominal portion. Below, the two pelvic sympathetic trunks converge, and end on the front of the

coccyx The coccyx ( : coccyges or coccyxes), commonly referred to as the tailbone, is the final segment of the vertebral column in all apes, and analogous structures in certain other mammals such as horses. In tailless primates (e.g. humans and othe ...

in a small ganglion, the ganglion impar, also known as azygos or ganglion of Walther.

Clinical significance

A study found that in some cases a single injection of

nerve block Nerve block or regional nerve blockade is any deliberate interruption of signals traveling along a nerve, often for the purpose of pain relief. Local anesthetic nerve block (sometimes referred to as simply "nerve block") is a short-term block, ...

at the ganglion impar offered complete relief from

coccydynia Coccydynia is a medical term meaning pain in the coccyx or tailbone area, often brought on by a fall onto the coccyx or by persistent irritation usually from sitting. Synonyms Coccydynia is also known as coccygodynia, coccygeal pain, coccyx pain, ...

References

* Munir MA, Zhang J, Ahmad M. (2004)
A modified needle-inside-needle technique for the ganglion impar block.
Can J Anaesth. 2004 Nov;51(9):915-7.

External links

"Ganglion Impar Injections to Treat Tailbone Pain" at www.TailboneDoctor.com

* * ttp://emedicine.medscape.com/article/309486-overview Tailbone pain (coccyx pain, coccydynia)Peer-reviewed medical article online a
eMedicine (Medscape)
Autonomic ganglia {{Neuroanatomy-stub