This is intended only as an outline, not a detailed account,
and questions concerning your individual situation should be
directed to your medical professional. Refer to the
glossary for the definition of terms with which you are
unfamiliar.
ANATOMY AND PHYSIOLOGY OF SPINAL CORD INJURY
The spinal cord is a flexible rope-like bundle of nerves that
extends from the brain down the spinal column, or "back
bone". The purpose of the spinal cord is to carry
information from all parts of the body to the brain, and then
back down again. As it travels from the brain downwards,
the spinal cord gives off many pairs of nerves (one member of a
pair on the right side and one on the left) which extend to
specific regions of the body. These nerves are arranged so
that those that are given off highest go to the highest parts of
the body such as shoulder and neck regions, and those that are
given off lower go to lower regions of the body. These
nerves can carry sensory information such as heat, touch, and
pressure to the spinal cord to be sent to the brain, as well as
movement information from the brain and spinal cord back to the
individual muscles.
The spinal cord is housed inside the tunnel-like spinal column or
backbone which is really made up of many small bones called
vertebrae. These vertebrae are stacked on each other and are
held together in a straight line with strong fiber bands or
ligaments. The column of vertebrae extends from the base of
the skull to the tailbone. There are roughly as many pairs of
nerves coming off the spinal cord as there are vertebrae. These
vertebrae are divided up according to the part of the body in which
they are located: The first seven vertebrae are in the neck
region and are called cervical vertebrae. They are numbered
C1,C2, C3.... C7 (C for cervical). Next come the thoracic or
chest region vertebrae. There are twelve of these, T1 through
T12. The lower back or lumbar region has five vertebrae, L1 through
L5. Next come the sacral vertebrae, S1 through S5; and
finally, at the tip of the spine, or coccyx, comes the coccygeal
vertebrae. The nerves that are given off from the spinal cord
leave the spine in the small spaces between adjacent vertebrae.
Only one pair of nerves leaves each space. The small sections
of spinal cord that give rise to each pair of nerves have the same
descriptive names as the vertebrae which are next to each nerve pair
as they leave the backbone.
Injuries to the spinal cord most often occur when there is a
sharp blow on the back, neck, head, or other parts of the body
which fractures one or more vertebrae or injures the ligaments
holding them in a straight line. If a vertebrae moves out
of alignment too much, or if bone chips from broken vertebrae
become lodged against the spinal cord, the spinal cord will
become damaged. The nerve bundles that make up the spinal
cord may be cut or bruised to the point that they will not be
able to carry the information signals normally as they used to.
In such cases, the injured person will not be able to move those
muscles that received their nerve supply from the brain through
the damaged area. He also will not be able to feel
anything below the point of injury, since the nerves that
carried sensory information from the skin to the brain are no
longer intact.
Immediately after injury to the spinal cord, there is usually complete loss of all sensation
and movement below the point of injury.
In some cases, the injury to the spinal cord is not so
severe as to disrupt all of the nerve bundles in the spinal
cord. After the initial shock wears off in these
instances, there will be a return of feeling and function to
those areas whose nerve supplies have not been disrupted.
However, in those cases where the injury is complete and
involves all nerve bundles in the spinal cord there will be
no return of either feeling or function. Unlike many
other tissues in the body, spinal cords do not regenerate
after they have been severed. If a spinal cord has
been cut, the cut ends will not rejoin or grow back
together. Instead, the part furthest from the brain or
spinal cord simply withers and dissolves away. If the
spinal cord is not completely cut, the part closest to the
brain and spinal cord above the injury will attempt to grow
back across the damaged area to the same tissues it supplied
before, but this happens only in a few cases. When
this does happen, there is a partial return of function and
feeling depending on the severity of the injury.
However, this very, very rarely returns to even near normal.
After the initial spinal shock has worn off, there are
sometimes feelings of pain, burning or tingling in the lower
parts of the body, even though all of the nerve pathways have
been destroyed in the spinal cord. While this is not fully
understood at this time, there are several possible
explanations. It may be that the cut end of the nerves in
the spinal cord are irritated and send pain signals to the
brain. A second possibility might be if there are no
impulses sent up from the severed nerve ending, the brain may
interpret this decreased input as pain. A third possible
explanation is that there must still be some nerve fibers intact
that carry pain impulses to the brain. These may be in the
autonomic (involuntary) nervous system which is outside the
spinal column.
Many patients with a spinal cord injury will experience
muscle spasms in the body regions in which he has no feeling or
muscle control. This is known as spasticity, and it, too,
occurs only after spinal shock has worn off. Often when
the patient or his family first see this movement they interpret
it as the first sign of the patient's ability to walk again, but
this interpretation is not correct. Spasticity is
completely involuntary. The patient is not consciously trying to
move his limbs, and in fact, he cannot prevent them from moving.
Spasticity occurs because although the control signals from the
brain cannot reach the spinal cord level that controls the
muscle, the nerves from the spinal cord itself to the muscle are
still intact. Therefore, there can be reflex movement, but
no control of that movement.
Spasticity affects not only the muscles of the arms, legs and
trunk, but also the muscles of the urinary bladder and
intestine. While at first such spasms in the bladder and
bowel may result in losing the urinary and bowel contents at
inconvenient times, these same spasms can be helpful later on
since they can be timed or "retrained" to occur at
convenient and predictable times. For more information,
see the section on bowel management and bladder training, and
discuss this with your nurse. Spasticity can be controlled
to some extent by medication. Talk with your nurse and
doctor for more information on medication.
