Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Autonomic Dysreflexia of the Spinal Cord


Michael Rubin

, MDCM, New York Presbyterian Hospital-Cornell Medical Center

Last full review/revision Jun 2021| Content last modified Jun 2021
Click here for the Professional Version

Autonomic dysreflexia of the spinal cord is an overreaction of the autonomic nervous system to a spinal cord injury, causing life-threatening high blood pressure (hypertension).

Autonomic dysreflexia occurs 1 month to 1 year later in 20% to 70% of people who have had a spinal cord injury.

The autonomic nervous system is the part of the nervous system that regulates body processes, such as blood pressure, urination, bowel movements, digestion, erection, breathing, vision, sweating, and salivation. When the spinal cord is injured, certain nerves in the autonomic nervous system may overreact to the injury, causing blood vessels to narrow and blood pressure to increase. Normally, other autonomic nerves send signals down the spinal cord to widen blood vessels, allowing the blood vessels to carry more blood and thus lower blood pressure. However, when the spinal cord is injured, nerve signals cannot always travel down the spinal cord to widen blood vessels, and blood pressure may remain high.

Autonomic dysreflexia may be triggered by


Symptoms of autonomic dysreflexia vary. They usually begin suddenly and occur intermittently.

People with this disorder may have headaches. They may feel nauseated and vomit. They may sweat profusely and be flushed. The skin may be dry and pale. Other symptoms include problems with vision, nasal congestion, and feelings of anxiety and doom.

High blood pressure may suddenly increase even more (called hypertensive crisis). Hypertensive crisis is life-threatening. People with hypertensive crisis may have a severe, throbbing headache, blurred vision, confusion, chest pain, shortness of breath, and seizures.


  • A doctor's evaluation

Doctors suspect autonomic dysreflexia when people have a spinal cord injury in the upper back and very high blood pressure, especially if they also have a distended bladder or intestine.

They also check for possible triggers of autonomic dysreflexia, such as a distended bladder.


  • Correction of the cause

  • Control of blood pressure

Doctors remove or correct the problem causing autonomic dysreflexia.

Very high blood pressure is immediately treated with drugs that work quickly, such as nitroglycerin, hydralazine, labetalol, or nifedipine.

Doctors may refer pregnant women to an obstetrician who specializes in treating disorders such as autonomic dysreflexia.

OnabotulinumtoxinA (a drug used to block nerve activity), injected into the main bladder muscle, may help prevent episodes of autonomic dysreflexia.

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read

Test your knowledge

Bell Palsy
Bell palsy is sudden weakness or paralysis of the muscles on one side of the face due to malfunction of the seventh cranial nerve. This nerve moves facial muscles, stimulates salivary and tear glands, detects tastes, and controls a muscle involved in hearing. Which of the following is often the first symptom of Bell palsy?
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID