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:
 Hypertensive emergency: the person's blood pressure gets very high all of a sudden.  The blood pressure can get so high that it can cause a stroke.  
 bradycardia, a slow heart rate.  If the heart beats too slowly, the rest of the body cannot get enough blood or oxygen.  This is dangerous, because every part of the body needs blood (which carries oxygen) to survive.  For example:
 If the brain does not get enough oxygen, a person can get brain damage or die.  
 If the heart does not get enough oxygen, it can stop beating normally or even stop beating completely.
 Bad headaches
 Very bad sweating
 Stuffy nose
 Skin flushing (redness) above the level of the spinal injury
 anxiety
 Thinking problems

 Causes 
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.

References

Category:Medical emergencies
Category:Diseases and disorders of the nervous system