Coccygeal plexus

The coccygeal plexus is formed by the anterior rami of S4-S5 in combination with the coccygeal nerve and is described as supplying the skin of the post anal region.

Gross anatomy

Origin

The plexus consists of a minute network of nerve fibres contributed by the anterior rami of S4, S5 and the coccygeal nerve ¹. 

Course

The coccygeal nerves emerge from the conus medullaris before descending within the cauda equina and exiting at the sacral hiatus with the S5 roots ³. S5 travels superior to the transverse process of the first coccygeal vertebra while the coccygeal nerve travels inferior. A small branch from S4 also joints to form the coccygeal plexus upon the pelvic surface of coccygeus ^2,3.

One cadaveric study found that unlike standard descriptions of the coccygeal plexus however, the plexus formed within the coccygeus muscle rather on the surface in a manner more similar to that of the lumbar plexus and the psoas muscle ⁴. 

Branches

• Anococcygeal nerves

Supply

Anococcygeal nerve branches of the coccygeal plexus have a variable description of supply ⁴. Typically they are described as supplying the post anal skin between the tip of the coccyx and the anus ¹. Some authors also describe these nerves as supplying the coccygeus muscle, part of the levator ani, the posterior extremity of the external anal sphincter, and the sacrococcygeal joint ^2,3.