In spinal cord injury, autonomic dysreflexia occurs in patients with injury above which level?

• A. Injury below T6.
• B. Only in cervical injuries.
• C. Only in upper lumbar injuries.
• D. Occurs in patients with spinal cord injury above T6.

Answer: (D)

Autonomic dysreflexia happens when there is a loss of brain control over sympathetic nerves below the level of spinal cord injury. When the injury is above about the T6 level, a noxious or even minor stimulus below the injury can trigger a massive, unregulated sympathetic response in the spinal segments from roughly T5 to L2. Because the brain can’t modulate this below-the-lesion activity, blood vessels below the injury constrict strongly, causing a sudden and dangerous rise in blood pressure. The heart may slow down (bradycardia) in response to the high blood pressure via a parasympathetic reflex, but this does not rectify the widespread vasoconstriction below the lesion. That’s why autonomic dysreflexia is classically seen in injuries above T6. If the injury is below that level, the pathways that would allow this unregulated discharge are not disrupted in the same way, so the syndrome is much less likely.