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Autonomic dysreflexia (AD) is a condition in which your involuntary nervous system overreacts to external or bodily stimuli. It’s also known as autonomic hyperreflexia. This reaction causes:
The condition is most commonly seen in people with spinal cord injuries above the sixth thoracic vertebra, or T6. It may also affect people who have multiple sclerosis, Guillain-Barre syndrome, and some head or brain injuries. AD can also be a side effect of medication or drug use.
AD is a serious condition that’s considered a medical emergency. It can be life-threatening and result in:
To understand AD, it’s helpful to understand the autonomic nervous system (ANS). The ANS is the part of the nervous system responsible for maintaining involuntary bodily functions, such as:
There are two branches of ANS:
The SANS and PANS operate in opposite ways. This maintains the balance of the involuntary functions in your body. In other words, if the SANS overreacts, the PANS can compensate for it.
Here’s an example. If you see a bear, your sympathetic nervous system might initiate a fight-or- flight reaction. This would cause your heart to beat faster, your blood pressure to rise, and your blood vessels to get ready to pump more blood. But what if you realize you were mistaken and it wasn’t a bear? You wouldn’t need the stimulation of your SANS, so your parasympathetic nervous system would jump into action. Your PANS would bring your heartbeat and blood pressure back to normal.
AD interrupts both the sympathetic and the parasympathetic nervous systems. This means that the body’s SANS overreacts to stimuli, such as a full bladder. What’s more, the PANS can’t effectively stop that reaction. It may actually make it worse.
Your lower body still generates a lot of nerve signals after a spinal cord injury. These signals communicate your bodily functions, such as the status of your bladder, bowels, and digestion. The signals can’t get past the spinal injury to your brain.
However, the messages still go to the parts of the sympathetic and parasympathetic autonomic nervous systems that operate below the spinal cord injury. Signals can trigger the SANS and PANS, but the brain can’t appropriately respond to them so they no longer work effectively as a team. The result is that the SANS and PANS can get out of control.
The symptoms of AD may include:
Triggers of AD in people with spinal cord injuries can be anything that generates nerve signals to the SANS and PANS, including:
AD requires an immediate medical response, so your doctor will usually treat the condition on the spot. Treatment is based on the apparent symptoms, as well as pulse and blood pressure readings.
Once the immediate emergency passes, your doctor will probably want to do a thorough examination and run diagnostic tests. These tests can help your doctor determine the exact cause and rule out other possible causes.
The goal of emergency treatment is to lower your blood pressure and eliminate the stimuli triggering the reaction. Emergency measures may include:
Long-term treatment and prevention should identify and address the underlying issues that trigger AD. A long-term treatment plan might include:
The outlook is more uncertain if your condition is due conditions that are hard to control or unknown causes. Repeated episodes of uncontrolled spikes or drops in blood pressure can result in strokes or cardiac arrest. Work with your doctor to identify your triggers and take precautionary steps.
If you can manage the triggers for AD, the outlook is good.
Written by: Christine Case-Lo
Medically reviewed on: Apr 21, 2017: William Morrison, MD
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