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autonomic hyperreflexia

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Autonomic nervous system

Alternative Names 
autonomic dysreflexia, dysreflexia, hyperreflexia

Autonomic hyperreflexia is an abnormal triggering of the autonomic nervous system that can occur 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 blood pressure 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 normal.

When a person has a spinal cord injury with damage to nerves in the spinal cord, this control can be lost. 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 cannot easily cause it to come back down.

What are the signs and symptoms of the disease? 
Autonomic hyperreflexia can cause the person's blood pressure to rise to a dangerous level. Symptoms may include: The severity of the symptoms can depend on how high the blood pressure goes. The symptoms go away quickly once the pressure drops.

What are the causes and risks of the disease? 
Below the level of damage in the spinal cord, the person usually is paralysed 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 who have menstrual cramps may have autonomic hyperreflexia. Sometimes the trigger is as simple as accidentally sitting on a hard object or having clothing bunched up.

What can be done to prevent the disease? 
A person with a spinal cord injury needs to learn the symptoms and causes of autonomic hyperreflexia. Keeping the bladder and bowel empty, taking good care of the skin, and avoiding infections are very important.

How is the disease diagnosed? 
Usually the person begins to feel the symptoms and quickly recognises the autonomic hyperreflexia. Checking the blood pressure can confirm the hyperreflexia. It is important to begin immediately to look for the cause and fix it.

What are the long-term effects of the disease? 
Once the cause of the autonomic hyperreflexia is removed, the condition goes away quickly. There are no long-term effects if the hyperreflexia is treated promptly. If treatment is not quick enough or is inadequate, the person may have a stroke. The stroke may cause speech impairments, cognitive impairments, and mobility impairments.

What are the risks to others? 
There are no risks to others.

What are the treatments for the disease? 
Autonomic hyperreflexia is a medical emergency. If the blood pressure stays high or continues to go up, a stroke can occur. The good news is that it is easy to treat.

The best treatment is to remove whatever is causing the autonomic hyperreflexia. This means emptying the bladder or bowels and making sure the person is not sitting on bunched-up clothing or a hard object. If the person is lying down, sitting up can help lower the blood pressure. Once the cause is removed, the symptoms immediately improve.

If the cause cannot be found, or the problem persists, it is important to contact emergency medical services immediately. Medications can be used to bring the blood pressure down to normal.

What are the side effects of the treatments? 
Side effects vary depending on the medications used to lower the blood pressure, but may include allergic reactions.

What happens after treatment for the disease? 
Autonomic hyperreflexia quickly goes away when the cause is removed. It is important to remember that the problem can return, so care must always be taken to prevent another episode.

How is the disease monitored? 
Usually, the person will notice symptoms as they occur and make sure the problem is quickly taken care of. It's a good idea to notify the doctor when an episode occurs unexpectedly. Any new or worsening symptoms should be reported to the doctor.

Reviewer: eknowhow Medical Review Panel
Editor: Dr John Hearne
Last Updated: 25/04/2005
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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