What is Autonomic Dysreflexia?
Autonomic dysreflexia means over-activity of the autonomic nervous system – the part of the system that controls things you don’t have to think about, like heart rate, breathing, digestion, etc.
Anything that would normally be painful, uncomfortable or physically irritating may cause dysreflexia following SCI (see the section on Causes for more detail).
Normally sensory nerves would send messages to the brain but after SCI the nerves below the level of the injury are no longer in communication with the brain. So the message about the problem is prevented from getting there by the damage to the spinal cord.
Since the impulses cannot reach the brain, a reflex is activated that increases activity of the sympathetic portion of the autonomic nervous system.
- This results in spasms and a narrowing of the blood vessels, which causes a rise in blood pressure.
- Nerve receptors in the heart and blood vessels detect this rise in blood pressure and send a message to the brain.
- The brain then sends a message to the heart, causing the heartbeat to slow down and the blood vessels above the level of injury to dilate.
- However, the brain cannot send messages below the level of injury, due to the spinal cord lesion, which means blood pressure cannot be regulated and continues to rise.
This is what can lead to serious problems if the trigger is not identified and resolved.
(Includes information from The Christopher and Dana Reeve Foundation website)