What is Autonomic Dysreflexia & How is it Treated? | How Does Autonomic Dysreflexia Happen?

Autonomic dysreflexia is a medical condition in which the involuntary nervous system starts overreacting to any bodily or external stimuli.^(1,2,3) This is commonly observed in people who have injured their spinal cord, especially in the upper back. Also known as autonomic hyperreflexia, this condition can cause the following:^(4,5)

• Slow down your heartbeat
• Dangerously high spike in your blood pressure
• Constriction of the peripheral blood vessels
• Other changes in the autonomic functions of the body

The condition is usually observed in people who have spinal cord injuries located above the T6 or the sixth thoracic vertebra. It is also commonly seen in people who have Guillain-Barre syndrome, multiple sclerosis, and other types of brain or head injuries. Autonomic dysreflexia can also happen as a side effect of certain medications or drug use.

Autonomic dysreflexia can be a serious condition if left untreated. It should be considered as a medical emergency as it can be life-threatening and cause the following: ^(6,7)

• Retinal hemorrhage
• Stroke
• Cardiac arrest
• Pulmonary edema

If you get autonomic dysreflexia because you have injured your spine either around the bottom or above the shoulder blades, you can start to lose muscle control and feeling below that damaged area. However, if the nerves of that location are still trying to send signals to the brain, this can make the body do wrong things or movement. For example, your blood vessels may start to react to these faulty signals and start becoming narrower, which can cause an increase in your blood pressure. Your brain will try to bring down your blood pressure, but its message may not be able to get past the damaged part of the spinal cord. Persistent high blood pressure can lead to a stroke or heart attack.⁽⁸⁾

If you want to understand this condition, you have to first understand how the autonomic nervous system functions. The autonomic nervous system is the part of your nervous system that helps maintain involuntary body functions, including:

• Digestion
• Blood pressure
• Breathing and heart rates
• Body temperature
• Urination
• Defecation
• Production of body fluids
• Balance of electrolytes and water
• Metabolism
• Sexual response

There are two parts of the autonomic nervous system. These are:^(9,10,11)

• Sympathetic autonomic nervous system (SANS)
• Parasympathetic autonomic nervous system (PANS)

The sympathetic autonomic nervous system and the parasympathetic autonomic nervous system function in entirely opposite ways. The autonomic nervous system maintains the balance of all the involuntary functions of the body. For example, if the sympathetic autonomic nervous system starts to overreact, the parasympathetic autonomic nervous system has to compensate for it. Consider this, if you come face to face with a bear, your sympathetic autonomic nervous system is likely to initiate a fight or flight reaction. This would cause your blood pressure to go up, your heart to beat faster, and your blood vessels get ready to start pumping more blood throughout the body. However, what happens when you realize that it was not a bear and you were mistaken? You would then not need the stimulation of the sympathetic autonomic nervous system, and your parasympathetic autonomic nervous system will work to bring down your blood pressure and lower your heartbeat back to normal.⁽¹²⁾

In people with autonomic dysreflexia, both the sympathetic and parasympathetic autonomic nervous systems get disrupted. This means that the sympathetic nervous system overreacts to any stimuli, such as a full bladder. At the same time, the parasympathetic nervous system is not able to effectively stop the overreaction, but it actually makes it worse.

Though the lower body still continues to generate a lot of nerve signals even after the injury to the spinal cord, these signals are not able to get past the spinal injury to reach the brain. This can include signals that communicate bodily functions like the status of the bowels, bladder, digestion, and many others.

These messages, though, are able to reach the parts of the sympathetic and parasympathetic autonomic nervous systems that are functioning below the spine injury. So while the signals trigger both the sympathetic and parasympathetic nervous systems, but the brain is not able to respond to them, which is why they are no longer able to work effectively. The result of this is that the sympathetic and parasympathetic autonomic nervous systems can get out of control and stop functioning properly. Symptoms of this may include slowing down of the heart rate because the pressure sensors are located in the carotid arteries.^(13,14)

The first signs of this condition are usually a flushed feeling or a persistent pounding headache. The other symptoms of autonomic dysreflexia may include:

• High blood pressure with systolic readings of over 200 mmHg
• Slow or irregular heartbeat
• Anxiety
• A pounding headache
• Nasal congestion
• Flushing of the skin
• Lightheadedness
• Confusion
• Profuse sweating, especially on the forehead
• Dizziness
• Dilated pupils
• Blurry vision
• Trouble breathing
• Goosebumps on the lower part of the body
• Stuffy nose

When you have autonomic dysreflexia, a trigger as simple as having an ingrown toenail or a full bladder can send the nervous system responses into an overdrive. Some of the causes that may trigger off the condition may include:

• Kidney or bladder stones
• Constipation
• Hemorrhoids
• Pressure sores
• Blistered or irritated skin
• Inserting a catheter or medical tube
• A blocked catheter
• Urinary tract infection
• Sunburn or burns from hot water
• Menstrual cramps
• Tight clothing
• Sexual stimulation
• Pressure on the scrotum
• Bowel impaction

Your doctor will carry out a thorough physical examination and measure your blood pressure while they try to diagnose if you have autonomic dysreflexia. They will check if there is any blockage or fullness of the bladder and bowels. They will also order imaging tests like an ultrasound or X-rays or other laboratory tests to examine your blood or urine.

Autonomic dysreflexia needs to be treated immediately, and your doctor will usually start treatment of the condition on the spot.

Treatment for autonomic dysreflexia depends on your symptoms, your heart rate, and blood pressure readings. The ultimate goal of immediate treatment for autonomic dysreflexia is to lower your blood pressure and to eliminate the stimuli that are causing your nervous system to overreact. Some of the emergency treatment measures that may be taken include:

• Removing any tight clothes and socks
• Moving the person into a sitting position to allow the blood to flow to your feet
• Treatment for any fecal impacting
• Draining a distended bladder with a catheter or removing any blockage in the catheter
• Removing any other triggers, such as objects touching your skin or drafts of air blowing on your
• Administering vasodilators or other medications to control your blood pressure. If the problem is severe, your doctor may want to monitor you for your blood pressure for at least 2 to 48 hours.

Long-term treatment for autonomic dysreflexia and prevention focuses on identifying and addressing the underlying issues that are causing your condition. A long-term treatment plan for autonomic dysreflexia may include:

• Medications for high blood pressure
• Changes in your diet or medication to improve elimination
• Better management of urinary catheters
• Self-management to avoid known triggers
• Medication or putting in a pacemaker for stabilizing the heartbeat

The long-term outlook for autonomic dysreflexia is uncertain if your condition is caused by situations that are hard to control or some unknown causes/triggers. Repeated episodes of uncontrolled drops or spikes in blood pressure can even cause cardiac arrest or stroke.

You have to work together with your doctor to identify the potential triggers and take the precautionary steps accordingly. Managing the triggers for autonomic dysreflexia can lead to a good outlook for this condition.

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