Autonomic Dysreflexia: Definition & Symptoms

Instructor: Danielle Haak

Danielle has a PhD in Natural Resource Sciences and a MSc in Biological Sciences

Autonomic dysreflexia is a serious condition where the body's blood pressure rises to dangerous levels. Read this lesson to learn about why this happens, who's at risk, and what the symptoms are.

What is Autonomic Dysreflexia?

Autonomic dysreflexia (referred to as AD throughout this lesson) is a condition where the body's blood pressure rises to dangerous levels. It most often affects people who have suffered a spinal cord injury, specifically the thoracic nerves of the spine at the T-6 level or higher, as well as those with multiple sclerosis, Guillain-Barre syndrome, or head/brain injuries. AD may also occur as a side effect of medication or due to drug abuse.

One of the ways the body controls blood pressure is by tightening or loosening muscles around the blood vessels. When vessels are tightened or constricted, blood pressure rises because blood is trying to move through a narrower space (and vice versa - loosened blood vessels cause blood pressure to drop). This mechanism relies on healthy communication between the heart and the brain so that the blood vessels are widened or narrowed at the right time with the sympathetic nervous system. However, when there's been a spinal cord injury, the signals informing the blood vessels to loosen or relax can't get through, causing vessels to stay tightened. This heart-brain feedback loop is disrupted. As a result, the autonomous (involuntary) nervous system is out of whack, and the sudden elevated blood pressure can lead to stroke, heart attack, retinal hemorrhage, pulmonary edema, or even death.

Causes of Autonomic Dysreflexia

AD usually occurs when there is some kind of negative stimulus below the site of the injury. A healthy individual would normally feel this stimulus, but in this case, the injury blocks them from feeling it. The most common causes of this irritating stimulus, which causes a rise in blood pressure, include the bladder or bowel overstretching or becoming irritated, a skin disorder or infection, broken bones, overstimulating sexual activity, abdominal conditions, menstrual cramps, or ovarian cysts.

Autonomic dysreflexia is caused by a disruption in the brain-heart feedback loop, causing blood pressure to remain elevated.

Symptoms of Autonomic Dysreflexia

Any of the stimuli discussed in the causes section can lead to hypertension (high blood pressure), and hypertension displays a number of symptoms. These can include headaches, flushed or blotchy skin (especially the face), sweating above the site of the injury, having a stuffy or runny nose, nausea, dilated pupils, anxiety, lightheadedness, confusion, goosebumps below the site of the injury, or having cold and clammy skin.

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