Autonomic dysreflexia (AD) is when your involuntary nervous system overreacts to external or bodily stimuli. It is a serious condition considered a medical emergency.

AD is also known as autonomic hyperreflexia.

This reaction causes:

  • a dangerous spike in blood pressure
  • slow heartbeat
  • narrowing of your peripheral blood vessels
  • other changes in your body’s autonomic functions

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-Barré syndrome, and some head or brain injuries. AD can also be a side effect of medication or drug use.

AD can be life threatening and result in:

  • stroke
  • cardiac arrest
  • retinal hemorrhage, a serious eye condition
  • pulmonary edema, when your lungs fill with fluid

The symptoms of AD may include:

  • a pounding or throbbing headache
  • flushed skin
  • irregular or slow heartbeat
  • high systolic blood pressure
  • anxiety and apprehension
  • nasal congestion
  • excessive sweating, particularly on the forehead
  • dizziness or lightheadedness
  • confusion
  • dilated pupils

A severe headache is usually the first sign of AD. Your lower body may be pale, cool to the touch, or sweaty.

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:

  • blood pressure
  • heart and breathing rates
  • body temperature
  • breaking down food into energy and using that energy in the body
  • balancing water and electrolytes
  • urination
  • defecation
  • sexual response

There are two branches of ANS:

  • sympathetic autonomic nervous system (SANS)
  • parasympathetic autonomic nervous system (PANS)

How they typically work

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.

What happens with AD

AD interrupts both the sympathetic and 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.

Your heart rate may slow down radically because pressure sensors located in your major arteries (called baroreceptors) respond to the abnormally high blood pressure by sending a signal to your brain. Your brain then tries to lower your blood pressure by slowing down your heart.

Triggers of AD in people with spinal cord injuries can be anything that generates nerve signals to the SANS and PANS, including:

Problems related to the bladder

Bladder problems are the most common cause of AD. Around 85 percent of AD episodes are caused by issues such as:

Problems related to the bowels

Problems related to the skin

Other triggers include bone and joint injuries and pregnancy.

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. These measures may include:

  • sitting upright, or receiving assistance to sit upright, to help lower blood pressure
  • checking for bladder or bowel triggers and treating them as needed
  • removing tight clothes and socks
  • removing any other potential triggers, such as drafts of air blowing on you or objects touching your skin
  • administering medication to bring your blood pressure under control

If your blood pressure does not go down, your doctor will need to continue emergency treatment to prevent more serious complications.

Talk with your doctor about your triggers and how to treat them. In some cases, you can learn to treat AD episodes yourself. It’s important to have someone with you who can call for emergency assistance if your condition worsens. If the cause of AD is unknown or your treatment plan is not working, call your local emergency services immediately.

Long-term treatment and prevention can identify and address the underlying issues that trigger AD. A long-term treatment plan might include:

  • self-management to avoid triggers when possible
  • changes in medication or diet to improve bladder and bowel function
  • improved management of urinary catheters
  • medications for high blood pressure

If you’ve had an AD episode in the past, consider talking with your doctor about creating an emergency kit to carry with you. An emergency kit usually contains medication and supplies to begin treatment and an information sheet to tell emergency personnel what’s happening if you’re unable to communicate during an episode.

AD can cause other serious conditions that affect your:

  • brain
  • heart
  • eyes
  • lungs

People who experience episodes of AD have a significantly increased risk of stroke. They can be 3 to 4 times more likely to have a stroke than people without AD.

Other possible complications of AD include:

Immediate treatment is needed to help prevent severe outcomes. In rare cases, AD can be fatal.

The outlook is more uncertain if your condition is due to situations that are hard to control or the cause is unknown. 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 of AD, the outlook is good.