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Axonal damage, which prevents the transmission
of neural signals, causes most of the physical problems associated
with spinal cord injuries (12). It
was first believed that axonal communication was interrupted by
the initial impact to the spinal cord, but it is now known that
secondary injury contributes to the damage. During this time, the
transport of vital molecules and cell components to and from the
axons is disrupted, and axons slowly deteriorate (12,
21).
Because of axonal damage, all communication with the body below
the site of the injury is terminated. Thus, the degree of diminished
or lost sensation and movement is a direct result of the height
of the injury on the spinal cord (26,
5) This results in problems associated
with both the sympathetic and autonomic nervous systems (21,
31).
Damage of the sensory nerve fibers can
cause loss of sensations such as temperature, touch and pressure,
but in some cases it also results in pain (21,
31).
Other major consequences of damage to nerve fibers include:
1. Diminished
or lost breathing capacity. (21,
31).
2. Muscle
atrophy (31)
3. Loss
of bladder and bowel control:
Bowel and urinary control are both partially under autonomic control
and partially under voluntary control. As a result of spinal cord
injury the voluntary control of these functions is lost. The automatic
control of these processes continues, however, and the muscles in
the intestinal tract continue to empty the bowels (31).
Initially patients will not be able to recognize when their bowels
are full, and they must be put on a schedule for regular waste elimination.
The urinary tract functions similarly. Patients are not able to
tell when their bladder is full and thus cannot prevent the bladder
from emptying. Loss of bladder control is called neurogenic bladder.
Many patients must use a catheter to empty the bladder and keep
urine from backing up in the kidneys, which could cause urinary
tract infections (16). The extent of
the injury determines the relative loss of bowel and bladder control.
4. Sexual
dysfunction: There are both
physical and emotional changes associated with sexual activities
as a result of spinal cord injuries. The extent of the changes depends
on the extent of the injury. As a result of spinal cord injury,
women retain the ability to become pregnant and give birth to healthy,
full-term babies. Men, however, have a reduced chance of producing
children through normal intercourse (26).
5. Spasticity:
During the initial weeks to months following a spinal cord injury
the body is in a state of "spinal shock" in which the normal reflexes
are lost below the site of injury. Once out of "spinal shock," the
reflexes return, and spasticity may develop. Spasticity is an exaggeration
of normal reflexes caused by the brains loss of control over reflexes
(31).
The spinal cord has primary control over many reflexes, but the
brain governs them as well. As a result of spinal cord injury the
information pathway to the brain is disrupted, and the brain can
no longer control reflexes associated with changes in the environment.
Because of this, reflex action in the spinal cord can become exaggerated
and result in spasticity. A spasm is caused by any stimulus entering
the spinal cord below the level of injury. This can be physical
stimulus such as cold air, or it can be an emotional stimulus such
as anxiety. As well as being a difficulty for patients, spasms can
also be of some help. They maintain the muscle tone in muscles that
would otherwise atrophy, and patients can learn to utilize spasms
to their advantage for performing tasks such as turning over in
bed or getting in and out of a wheelchair. Over time, patients learn
what stimuli cause spasms how to avoid them or utilize them (26).
6. Pressure
sores (also known as bedsores and decubitus ulcers):
Pressure sores are an indirect result of spinal cord injuries. They
are areas of skin that have broken down due to a reduced blood flow.
Pressure sores usually develop from sitting or lying in one position
for too long and they most often occur in places that support the
body weight (31).
These areas often lack fatty tissue to protect them from the pressure,
and as result, the bones compress the skin and blood flow is cut
off. Spinal cord patients are often unaware that they have remained
in one position too long, so they do not realize that areas of their
skin have been compressed too long (26).
7. Autonomic
Dysreflexia (AD) (also known as Hyperflexia): AD is a complication
of a spinal cord injury that causes increased blood pressure to
dangerous levels. It is the result of an irritating stimulus below
the level of the injury. The stimulus causes blood vessels to constrict
causing blood pressure to rise. In an uninjured spinal cord a set
of opposing responses cause the blood vessels to relax and blood
pressure to drop. In people who sustain spinal cord injuries at
the T-6 level or above, however, the message that initiates this
opposing response cannot pass through the injury and the vessels
remain constricted and blood pressure remains elevated. Some of
the nerves at the T-6 level also control the flow of blood to and
from the abdomen. Unregulated activity of these nerves can cause
the blood from the abdomen to flow to the rest of the body, which
increases blood pressure. If blood pressure is not controlled by
some external method, it could lead to a stroke or possible death
(22).
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