Nerves of Pelvis

Major nerves supplying the pelvis are:

• Cauda Equina
• Superior Gluteal Nerve
• Filum Terminale
• Pudendal Nerve
• Iliohypogastric Nerve

Cauda Equina

Cauda equina is the package of nerves comprised of the lumbar, sacral as well as coccygeal nerve roots coming from L2 to S5 creates cauda like a horse tail. Generally it starts at the level of L1/L2 disc space distal towards the conus medullaris. The spinal cord terminates at the lower border of the first lumbar vertebra where it blends to create the conus medullaris. The lumbar as well as sacral nerve roots which emerge from the lower portion of spinal cord create a bundle inside the spinal canal under the conus medullaris. This bundle of nerves is identical in appearance to a horse’s tail and is referred to as the cauda equina. Lumbar as well as sacral nerve roots exit behind the spinal canal, as well as send and collect nerve stimulus to and from the lower limbs along with pelvic organs.

Superior Gluteal Nerve

The superior gluteal nerve originates in the pelvis and supplies the gluteus medius, the gluteus minimus and the tensor fasciae latae muscle. Nerve roots of the sacral plexus forms the superior gluteal nerve.

The superior gluteal nerve, created by divisions via the dorsal branches of L4 to SI, exits the pelvic cavity via the greater sciatic foramen superior to the piriformis muscle and supplies muscles in the gluteal region, gluteus medius, gluteus minimus, and tensor fasciae latae (tensor of fascia lata) muscles.

The superior gluteal nerve ramifies in between the gluteal minimus and maximus muscles and disperses divisions to each of these muscles. The superior gluteal nerve ends by piercing and innervating the tensor fasciae latae muscle.

Filum Terminale

The conical shaped caudal end of the spinal cord lies on the rostral border of the second lumbar vertebra called the conus medullaris. A thin filament covered in pia and including glial cells, ependymal cells, and astrocytes arises out of the conus medullaris. This filament is referred to as die filum terminate internum. It expands via the conus medullaris and travels through the caudal end of the dural sac. At this level, a caudal thin elongation of the spinal dura, referred to as the coccygeal ligament (filum term inale externum) encompasses the filum terminale. The coccygeal ligament, along with the filum terminale in it, connects to the coccyx and, thus, supports the spinal cord together with the fluid-filled dural sac towards the caudal end of the vertebral canal.

The filum terminale is a fragile strand of fibrous tissue, around 20 cm in length, continuing down via the apex of the conus medullaris. It is among the alterations of pia mater. It provides longitudinal support to the spinal cord and also contains two parts:

• The upper part or filum terminale internum.
• The lower part or filum terminale externum.

Pudendal Nerve

The Pudendal nerve exits the main pelvic cavity via the greater sciatic foramen and is a division of the sacral plexus. It goes into the perineum via the lesser sciatic foramen after a brief route within the gluteal zone of the lower limb. Within the pudendal canal the nerve then travels forward and innervates the external anal sphincter along with the muscles as well as skin of the perineum through its branches.

The pudendal nerve travels among the piriformis muscle as well as coccygeus (ischiococcygeus) muscles and also exits the lower portion of the greater sciatic foramen in the pelvis. It bridges the lateral part of the sacrospinous ligament and returns to the pelvis via the lesser sciatic foramen.

Iliohypogastric Nerve

The iliohypogastric nerve is the first significant branch of the lumbar plexus. Iliohypogastric nerve is a sensory nerve which supplies lateral and anterior cutaneous branches supplying the posterolateral gluteal skin as well as skin in the pubic region.

The iliohypogastric nerve generally emerges from the ventral ramus of the LI spinal nerve. Iliohypogastric nerve emerges via the upper lateral border of psoas major and intercrosses in front of quadratus lumborum and obliquely behind the lower renal pole. Above the iliac crest, it goes into the posterior part of transversus abdominis.In between the transversus abdominis and internal oblique, iliohypogastric nerve splits into lateral and anterior cutaneous branches.