Alternate Names : Autonomic Dysreflexia, Dysreflexia, Hyperreflexia
Autonomic hyperreflexia is an abnormal triggering of the autonomic
nervous system. It occurs after a spinal cord injury.
The body is unable to turn off the nerves that cause blood pressure to rise.
What is going on in the body?
Normally, the autonomic nervous system controls
automatically. It does this by commanding muscles around blood vessels to
tighten or relax in order to raise or lower blood pressure. The nervous system can
monitor blood pressure and continually adjusts the commands to keep blood pressure
When a person has a spinal cord injury,
it can cause damage to nerves in the spinal cord. And this results in a loss of control
in the nerves. This can happen
if the damage to the spinal cord is in the neck or upper back. The bones of the spine
are each labeled and numbered. Damage at the 6th thoracic bone or higher means
the person may develop this problem. If the damage is lower, autonomic hyperreflexia
will not be a problem.
In autonomic hyperreflexia, the autonomic nervous system can still
cause the blood pressure to rise. But it cannot easily cause it to come back down.
What are the causes and risks of the disease?
Below the level of damage in the spinal cord, the person usually is
paralyzed and cannot feel normal sensations. Autonomic hyperreflexia occurs
when an irritating stimulus occurs that the person cannot feel. The most common
cause is a very full bladder. The bladder sends signals through the nervous system
to the brain. The signals cannot get through because of the spinal cord damage.
The person cannot feel that the bladder is full and needs to be emptied. But the
automatic part of the nervous system that controls the blood pressure still gets
triggered and causes the blood pressure to go up.
Other common causes are a full bowel, an infection, or a sore on the
skin. Women with spinal cord injuries who have menstrual cramps may also have autonomic hyperreflexia.
Sometimes the trigger is as simple as accidentally sitting on a hard object or
having clothing bunched up.