Autonomic dysreflexia

Autonomic dysreflexia (AD), also called autonomic hyperreflexia, is a medical emergency. 
Who Gets Autonomic Dysreflexia?
AD usually happens in people with spinal cord injuries that have caused damage above the sixth thoracic vertebra (T6, which is about at the same level of the armpits). However, AD sometimes happens in people with spinal damage as low as their tenth thoracic vertebra (T10, which is about a few inches above the level of the belly button).
AD can also happen in people with diseases like multiple sclerosis (MS).
Symptoms.
Acute AD causes many symptoms. Some are very dangerous. These symptoms include:
What Causes Autonomic Dysreflexia?
Acute AD happens when the involuntary nervous system gets overexcited. The body's fight or flight response kicks in very strongly. 
Scientists think this happens because of afferent nerves. Afferent nerves are supposed to sense things (like touch) and send messages back to the brain and spinal cord so the brain can decide how to react. Scientists think that afferent nerves below the spinal cord injury cause blood pressure to get and stay high, by causing the blood vessels to get smaller. This is part of the fight or flight response.