Which level of spinal cord injury is most associated with autonomic hyperreflexia?

Which level of spinal cord injury is most associated with autonomic hyperreflexia?

• A. Above T6
• B. Below T6
• C. At T6
• D. Cervical level only

Answer: (A)

Autonomic hyperreflexia occurs when a spinal cord injury is high enough that the brain can no longer modulate sympathetic activity below the lesion. A noxious stimulus below the injury (like bladder distension or a pressure sore) triggers a powerful reflex sympathetic discharge, causing widespread vasoconstriction and a sudden, dangerous rise in blood pressure. Because the injury is above the level where descending control can reach, this sympathetic response is unopposed. The brain can mount a parasympathetic response above the injury (causing flushing, sweating, headache), but it cannot counteract the vasoconstriction below the lesion, so the hypertension persists. This is why injuries above the T6 level are most strongly associated with autonomic hyperreflexia. If the injury is below T6, some supraspinal modulation remains, making autonomic dysreflexia much less likely.

Autonomic hyperreflexia occurs when a spinal cord injury is high enough that the brain can no longer modulate sympathetic activity below the lesion. A noxious stimulus below the injury (like bladder distension or a pressure sore) triggers a powerful reflex sympathetic discharge, causing widespread vasoconstriction and a sudden, dangerous rise in blood pressure. Because the injury is above the level where descending control can reach, this sympathetic response is unopposed. The brain can mount a parasympathetic response above the injury (causing flushing, sweating, headache), but it cannot counteract the vasoconstriction below the lesion, so the hypertension persists. This is why injuries above the T6 level are most strongly associated with autonomic hyperreflexia. If the injury is below T6, some supraspinal modulation remains, making autonomic dysreflexia much less likely.