At the base of the spinal column, near the first lumbar vertebra, is a collection of nerves called the cauda equina. They are called this because they resemble a horse's tail. Just above the cauda equina, the spinal cord ends and it continues on as this collection of spinal nerves through the vertebral canal.

The cauda equina has approximately 10 fiber pairs at its base. These consist of three to five lumbar fiber pairs, five sacral fiber pairs, and one coccygeal nerve. The primary function of the cauda equina is to send and receive messages between the lower limbs and the pelvic organs, which consist of the bladder, the rectum, and the internal genital organs.

When these nerve roots become highly compressed, cauda equina syndrome may be diagnosed. This condition is considered serious, as the patient could permanently lose the functions of their bowel and bladder, and can lead to permanent paralysis of the legs. When cauda equina syndrome is diagnosed, surgery will generally be required to relieve the compression of the nerves.