Autonomic hyperreflexia with spinal cord injury.

Autonomic hyperreflexia occurs in up to 85 percent of individuals with spinal cord injuries above the major splanchnic sympathetic outflow. In such cases, paroxysmal reflex sympathetic activity develops in response to noxious stimuli below the level of the neurologic lesion. The clinical features of autonomic hyperreflexia are due largely to reflex sympathetic adrenergic and cholinergic discharges with dysfunctional supraspinal regulatory control. Cephalgia, diaphoresis, flushing, tachycardia or bradycardia, and paroxysmal hypertension are most commonly observed. Although a variety of stimuli can provoke autonomic responses of variable magnitudes, bladder and bowel distention continue to account for most episodes. Removal of the offending stimulus is important to restoring the autonomic nervous system to its baseline activity. Current understanding of the pathophysiology, clinical features, and medical management of this fascinating but potentially serious complication of spinal cord injury are reviewed.