All About Autonomic Dysreflexia (or Hyperreflexia)

What Is Autonomic Dysreflexia (AD)?

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 a dangerous spike in blood pressure, rapid heartbeat, constriction of your peripheral blood vessels, and 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-Barre syndrome, and some head or brain injuries. AD can also be a side effect of medication or drug use.

AD is potentially life-threatening and can result in:

  • stroke
  • retinal hemorrhage
  • cardiac arrest
  • pulmonary edema

AD is a very serious condition, and it’s a medical emergency.

What Causes Autonomic Dysreflexia?

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To understand AD, it’s helpful to know understand the autonomic nervous system (ANS).

The ANS is the part of the nervous system responsible for involuntary bodily functions such as:

  • blood pressure
  • heart and breathing rates
  • body temperature
  • digestion
  • metabolism
  • balance of water and electrolytes
  • production of body fluids
  • urination
  • defecation
  • sexual response

There are two branches of ANS:

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

The SANS and PANS operate in opposite ways to maintain 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, and the PANS can’t effectively stop that reaction and may actually make it worse.

Your lower body still generates a lot of nerve signals after a spinal cord injury. These signals communicate the status of your bladder, bowels, digestion, and other bodily functions. The signals can’t get past the spinal injury to your brain.

However, they are still being sent to the parts of the sympathetic and parasympathetic autonomic nervous systems that operate below the spinal cord injury. Signals from your bodily functions can trigger the SANS and PANS, but the brain can’t appropriately respond to them. They can no longer work effectively as a team. The result is that the SANS and PANS can get out of control.

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

  • a distended bladder
  • a blocked catheter
  • urinary retention
  • a urinary tract infection
  • bladder stones
  • constipation
  • a bowel impaction
  • hemorrhoids
  • skin irritations
  • pressure sores
  • tight clothing

What Are the Symptoms of Autonomic Dysreflexia?

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The symptoms of AD may include:

  • anxiety and apprehension
  • irregular or racing heartbeat
  • nasal congestion
  • high blood pressure with systolic readings often over 200 mm Hg
  • a pounding headache
  • flushing of the skin
  • profuse sweating, particularly on the forehead
  • lightheadedness
  • dizziness
  • confusion
  • dilated pupils

How Is Autonomic Dysreflexia Diagnosed?

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Because AD requires immediate medical response, 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. This can help determine the exact cause and rule out other possible causes.

How Is Autonomic Dysreflexia Treated?

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The goal of emergency treatment is to lower your blood pressure and eliminate the stimuli triggering the reaction. Emergency measures may include:

  • moving you into sitting position to cause the blood to flow to your feet
  • removing tight clothes and socks
  • checking for a blocked catheter
  • draining a distended bladder with a catheter
  • removing any other potential triggers, such as drafts of air blowing on you or objects touching you skin
  • treating you for fecal impaction
  • administering vasodilators or other drugs to bring your blood pressure under control

How Can I Prevent Autonomic Dysreflexia?

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

  • changes in medication or diet to improve elimination
  • improved management of urinary catheters
  • medications for high blood pressure
  • medications or a pacemaker to stabilize your heartbeat
  • self-management to avoid triggers

What Is the Long-Term Outlook?

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The outlook is more uncertain if your condition is due to unknown causes or conditions that are hard to control. 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.

The outlook is good if you can manage the triggers for AD.

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