Cauda equina and Cauda equina syndrome

http://en.wikipedia.org/wiki/Cauda_equina
The cauda equina is a structure within the lower end of the spinal column
of most vertebrates, that consists of nerve roots and rootlets from above.
Cauda equina is sometimes considered as an extension of piamater of spinal
cord. The space in which the cerebro spinal fluid is present is actually
an extension of the sub arachnoid space.

In humans, because the spinal cord stops growing in infancy while the
bones of the spine continue growing, the spinal cord in adults ends at
about the level of the vertebra L1/L2 , and at birth at L3. However there
is some variation in adults and the cord may end anywhere between
vertebrae T12 to L3. Individual spinal nerve roots arise from the spinal
cord as they do closer to the head, but as the differential growth occurs
the top end of the nerve stays attached to the spinal cord and the lower
end of the nerve exits the spinal column at its proper level, this results
in a "bundle"-like structure of nerve fibres that extends caudally from
the end of the spinal cord, gradually declining in number further down as
individual pairs leave the spinal column. At the base of the Cauda Equina,
there are approximately 10 fibre pairs, 3-5 lumbar, 5 sacral, and the
single coccygeal nerve.

All these roots and rootlets down the vertebral column give the appearance
of a horse's tail, which is the meaning of the Latin name cauda equina.

Cauda equina is the part of the spinal cord where a spinal tap is
performed in order to get a sample of cerebral spinal fluid (CSF) for
diagnostic purposes.

http://en.wikipedia.org/wiki/Cauda_equina_syndrome
Cauda equina syndrome is a serious neurologic condition in which there is
acute loss of function of the neurologic elements (nerve roots) of the
spinal canal below the termination (conus) of the spinal cord.

After the conus the canal contains a mass of nerves (the cauda equina)
which travels caudally (toward the feet).

Any lesion which compresses or disturbs the function of the cauda equina
may disable the nerves although the commonest is a central disc prolapse.

Other causes include protrusion of the vertebra into the canal if weakened
by infection or tumor and an epidural abscess or hematoma.