Autonomic Dysreflexia

Medically Reviewed by Jabeen Begum, MD on February 08, 2024
Written by Matt Smith, Lori M. King, PhD
6 min read

Your autonomic nervous system controls things that your body does without having to think about it, such as breathing and digesting. Autonomic dysreflexia (sometimes also called hyperreflexia) is a serious medical problem that can happen when you’ve injured the spinal cord in your upper back. Autonomic dysreflexia makes your blood pressure dangerously high, often because it overreacts to something in your body below the damage in your spinal cord. An autonomic dysreflexia episode is an emergency and needs immediate medical attention because it can be life-threatening. High blood pressure , especially when it comes on fast, can give you a heart attack or a stroke.

It's especially common when your injury is at or above the sixth thoracic vertebra (T6) in your spine. Your T6 vertebra is at about the level of your shoulder blades. You may lose feeling and muscle control below the damaged spot, but the nerves are still there, sending signals back to the brain. This can make your body do the wrong thing. For example, your blood vessels may react to the faulty signals and become narrower, which makes your blood pressure go up. Your brain tries to lower your blood pressure, but its message can’t get past the damaged part of the spinal cord. More than half of people with a spinal cord injury in the upper back get it.

Your symptoms may appear suddenly and come and go. They may vary from person to person. For instance, some people have mild symptoms that they might ignore, while others have severe symptoms. Some symptoms may be triggered by different things. You may have a few, any, or all of the following symptoms:

  • High blood pressure that rises fast and may be 20-40 points (or 15-20 points in children) higher than your normal upper blood pressure number
  • Slow or fast heart rate
  • Severe headache that may be pounding
  • Nausea and vomiting
  • Changes in your vision, including blurred vision
  • Stuffy nose
  • Cold skin
  • Feelings of anxiety, apprehension, or uneasiness

Some specific symptoms that happen in your body above the level of your injury include:

  • Heavy sweating
  • Red, hot skin (flushing)
  • Goosebumps or hair standing up
  • Tingling sensations

Some symptoms that happen below the level of your injury include:

  • Dry, pale, or cool skin
  • Clammy skin
  • Narrowed blood vessels

Silent autonomic dysreflexia

Some people have high blood pressure without any symptoms. This is known as silent autonomic dysreflexia. If you've had a spinal cord injury, monitor your blood pressure during your normal activities and tell your doctor right away if your blood pressure changes a lot.

In people with a spinal cord injury, certain types of stimulation can cause their nervous system to overrespond. Usually, this stimulation is something that could damage tissues or cause pain. It also typically happens below the level of the injury. In response to this stimulus, your nervous system triggers a reflex that narrows all your blood vessels above the injury, which raises your blood pressure.

An autonomic dysreflexia episode can be caused by various types of stimulation, including:

Bladder triggers. These are the most common. It's usually something that keeps you from peeing, which leads to an overfull bladder. These include:

  • A kink or clog in your Foley catheter
  • Bladder spasms
  • Bladder stones
  • Urinary tract infections
  • Bladder testing, such as cystoscopy (a procedure where your doctor uses a small, flexible camera to look at the lining of your bladder) and urodynamic testing (tests that measure how well you store and release pee)

Bowel triggers. Most of these overstretch or irritate your bowel, such as:

  • Pooping quickly
  • Poop stuck in your rectum
  • An enema or the manual removal of poop
  • Gas and gas pain
  • Constipation
  • Diarrhea
  • Diverticulitis
  • Crohn's disease
  • Anal fissure
  • Hemorrhoids

Skin triggers, including:

  • Rashes
  • Bedsores
  • Cuts or bruises
  • Clothes that are too tight, lumpy, or baggy
  • An itch that you can't sense or scratch
  • Ingrown toenails

People with neurologic disease, stroke, or brain injury may also get autonomic dysreflexia episodes. Conditions that may make you more prone to episodes include:

  • Central nervous system tumor (intramedullary astrocytoma)
  • Multiple sclerosis
  • Guillain-Barre syndrome
  • Side effects from some medicines
  • Severe head trauma or brain injury
  • Subarachnoid hemorrhage
  • Use of some stimulant drugs, such as cocaine and amphetamines

Your doctor will likely diagnose you based on your:

  • Medical history, especially your history of a spinal cord injury
  • Current blood pressure compared to your usual blood pressure
  • Symptoms

If you have symptoms of autonomic dysreflexia but haven't had a spinal cord injury, your doctor will run tests to help them figure out the cause of your symptoms, including:

  • Blood and pee tests
  • Drug testing
  • CT or MRI scans
  • X-rays
  • Electrocardiogram (EKG)
  • Spinal tap
  • Tilt-table test

If you don't know what your triggers are or you can't figure out what's causing this episode, call 911 and go to the ER right away. You will need emergency treatment with fast-acting drugs, such as nitrates, hydralazine, labetalol, or nifedipine, to lower your blood pressure.

Autonomic dysreflexia posture

Sit upright with your legs dangling, and take off any tight clothes, jewelry, or devices. This helps blood flow down to your legs, which lowers your blood pressure. Monitor your blood pressure to make sure it goes down to your usual level.

Most episodes of autonomic dysreflexia will go away once you remove the stimulus or trigger. If you know your usual triggers, check for and fix any of those, for instance:

  • Check that your bladder can drain. If you have no or little urine output, insert a catheter.
  • Check your bowel for poop blockage. Remove the blockage if you have one.
  • Check your skin for wrinkles, constrictions, and tight clothes.

If this doesn't resolve your episode, continue to look for and remove any triggers. Continue to monitor your blood pressure for at least 2 hours after your blood pressure starts to come down.

If your blood pressure does not start to come down after taking these steps, call 911 and go to the ER.

Most people with autonomic dysreflexia do well as long as you:

  • Get emergency treatment as soon as possible if you have an episode
  • Get diagnosed and know how to recognize when you're having an episode
  • Are educated and trained on the potential triggers
  • Avoid triggers whenever possible

It's not always possible to prevent an autonomic dysreflexia episode. However, if you have a spinal cord injury, you may be able to lower your chance of having an episode in the following ways:

  • Use the bathroom on a regular schedule. Keep your bladder and bowels from becoming too full.
  • Eat a healthy diet with fiber to prevent constipation.
  • Manage any pain.
  • Take steps to prevent a urinary tract infection.
  • Take care not to get skin sores or ingrown toenails.
  • Carry an emergency treatment bag including information about autonomic dysreflexia, treatment instructions, and basic supplies to help you lower your blood pressure during an episode.

If you have an autonomic dysreflexia episode and don't get the treatment you need, you can have serious complications, including:

  • Hypertensive encephalopathy (brain dysfunction caused by severely high blood pressure)
  • Stroke
  • Heart attack
  • Seizure
  • Death

How common is autonomic dysreflexia?

Doctors estimate that about 48%-70% of people with a spinal cord injury above the T6 vertebra get autonomic dysreflexia. About 17,000 people in the U.S. have a spinal cord injury each year. Most spinal cord injuries are in the neck and upper back, which are the areas in the spine that put you at risk for autonomic dysreflexia.

What drugs should be avoided in autonomic dysreflexia?

Don't take sildenafil (Viagra), vardenafil (Levitra), or Tadalafil (Cialis) for at least 48 hours after you have an episode. These medicines activate your nervous system, which may make your blood pressure go up again.

What are the 6 B's of autonomic dysreflexia?

The six B's refer to an aid to help you remember the common triggers of an autonomic dysreflexia episode. They include:

  • Bladder (catheter blockage or bladder distension, stones, infection, or spasms)
  • Bowel (constipation, impaction)
  • Back passage (hemorrhoids, rectal fissures, or anal abscesses)
  • Boils (bed sores, infected ulcers)
  • Bones (breaks, dislocations)
  • Babies (pregnancy)

Autonomic dysreflexia makes your blood pressure dangerously high. It's usually caused by a spinal cord injury in your upper back, but it can also be caused by neurologic disease, stroke, or brain injury. Certain types of stimulation that happen below the level of your injury can trigger your nervous system to react to faulty signals. This may cause your blood vessels to become narrower, which makes your blood pressure go up. These triggers are usually things such as an overfull bladder, bowel issues, or skin irritation or injuries. Once you find out which stimulation triggers your episodes, you will be able to manage your condition by avoiding and correcting your triggers before your blood pressure goes up.